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Town of Amherst Subdivision By-Law
As adopted by Town Council June 21, 2004
And Approved by Provincial Director of Planning July 30, 2004
2
THIS IS TO CERTIFY that the following is a true
copy of the Town of Amherst's Sub-Division By-
Law as adopted at a duly called meeting of the
Town Council of the Town of Amherst duly held on
the 21st day of June , 2004.
GIVEN under the hand of the Town Clerk and
under the Corporate Seal of the Town this 6th
day of July , 2004.
______________________________________
Ed Childs
Town Clerk
Town of Amherst
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TABLE OF CONTENTS
SECTION 1: SHORT TITLE.........................................................................3
SECTION 2: INTERPRETATION...........................................................................3
SECTION 3: DEFINITIONS..........................................................................3
SECTION 4: GENERAL PROVISIONS ........................................... ..............6
SECTION 5: MUNICIPAL SERVICES ........................................... ................7
SECTION 6: PUBLIC OPEN SPACE ................................................. ..........9
SECTION 7: REQUIREMENTS FOR PRELIMINARY PLANS OF
SUBDIVISION .......................................................................11
SECTION 8: PROCEDURE FOR APPROVAL OF PRELIMINARY PLANS OF
SUBDIVISION.......................................................................11
SECTION 9: REQUIREMENTS FOR CONCEPT PLANS OF
SUBDIVISION........................................................................12
SECTION 10: PROCEDURE FOR APPROVAL OF CONCEPT PLANS OF
SUBDIVISION.......................................................................13
SECTION 11: REQUIREMENTS FOR TENTATIVE PLANS OF
SUBDIVISION .......................................................................15
SECTION 12: PROCEDURE FOR APPROVAL OF TENTATIVE PLANS OF
SUBDIVISION.......................................................................17
SECTION 13: REQUIREMENTS FOR FINAL PLANS OF
SUBDIVISION .......................................................................19
SECTION 14: PROCEDURE FOR APPROVAL OF FINAL PLANS OF
SUBDIVISION......................................................................21
SECTION 15: REPEAL OF SUBDIVISION.....................................................23
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LIST OF SCHEDULES
SCHEDULE "A" - Application For Subdivision Approval
SCHEDULE "B" - Notice of Approval
SCHEDULE "C" - Application for Approval of a Variance
SCHEDULE "D" - Application for Repeal of a Subdivision
SCHEDULE "E" - Repeal of a Subdivision
SCHEDULE "F" -Infrastructure Development Standards
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SUBDIVISION BY-LAW FOR THE
TOWN OF AMHERST
SECTION 1: SHORT TITLE
1.1
This By-Law may be cited as the "Subdivision By-Law" for the Town of Amherst.
SECTION 2: INTERPRETATION
2.1
In this By-Law the word "shall" is mandatory and not permissive. Words used in the
present tense shall include the future. Words used in the singular shall include the plural
except where otherwise indicated and words used in the plural number shall include the
singular. All other words shall carry their customary meaning except those defined
hereinafter.
2.2
SCHEDULES "A", "B", "C", "D", "E" and "F" attached hereto are adopted by
Resolution of Council and hereby declared to form part of this Bylaw.
2.3
This By-Law shall apply to the subdivision of all land within the Town of Amherst
and shall be administered by the Development Officer.
SECTION 3: DEFINITIONS
3.1
In these regulations,
(a)
"Act" means the Municipal Government Act (MGA), c. 18, Statutes of Nova
Scotia, 1998, as amended.
(b)
"Area of land" means any lot or parcel as described by its boundaries.
(c)
"Council" means the Council of the Town of Amherst.
(c)
"Contour" means a line joining like elevations as determined by a surveyor, or the
Nova Scotia Topographic Database.
(d)
"Cul-de-sac" means a local street, with only one connection to a thru street, and a
permanent circular turn around at its end.
(d)
"Department of the Environment" means the Nova Scotia Department of the
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Environment and Labour.
(e)
"Department of Transportation and Public Works" means the Nova Scotia
Department of Transportation and Public Works.
(f)
"Development Officer" means the officer, or assistant, who is appointed by
Council to administer the provisions of this Subdivision Bylaw.
(g)
"Director" means the Provincial Director of Planning.
(h)
"Engineer" means the engineer for the Town, and includes a person acting under
the direction of the engineer.
(i)
"Lot" means a parcel of land described in a deed or as shown on a registered plan
of subdivision.
(j)
"Lot Area" means the total horizontal area within the lot lines of a lot.
(k)
"Lot Frontage" means the length of a line joining the side lot lines and parallel to
the front lot line. Calculation of Lot Frontage for irregularly shaped lots shall be
the horizontal distance between the side lot lines as measured at a point, where a
line drawn perpendicular to a line joining the midpoint of the rear lot line and the
midpoint of the front lot line at a point equal to the required front yard. In
determining yard measurements the minimum horizontal distance from the
respective lot lines shall be used. Calculation of lot frontage for corner lots shall
be the horizontal distance between the side lot line and the flanking lot line.
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(l)
"Main Building" is the building in which the main use of the lot is carried out and
is not accessory to another building on the said lot.
(m)
"Municipal Planning Strategy and Land Use By-Law" means the Municipal
Planning Strategy and Land Use By-Law for the Town of Amherst.
(n)
"Public Sewer System" means any sanitary sewer system that is owned and
maintained by the Town.
(o)
"Public Storm Sewer System" means any storm sewer system that is owned and
maintained by the Town.
(p)
"Public Water System" means any water system that is owned and maintained by
the Town.
(q)
"Public street or highway" means any street or highway owned and maintained by
the Town of Amherst or the Department of Transportation and Public Works.
(r)
"Registry of Deeds" means the office of the registrar of deeds for the registration
district of Cumberland.
(s)
"Subdivider" means the owner, or owners agent, of the area of land proposed to
be subdivided.
(t)
"Subdivision" means the division of any area of land into two or more parcels,
and includes a re-subdivision or a consolidation of two or more parcels.
(u)
"Town" means the Town of Amherst.
(v)
"Thru street" means a street which has at least two connections to other thru
street(s).
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SECTION 4: GENERAL PROVISIONS for SUBDIVISION
4.1
All lots approved on a final plan of subdivision shall abut a public street.
4.2
All lots shall meet the applicable requirements contained in the Land Use By-law.
4.3
(a)
Notwithstanding the lot area and frontage requirements of Section 4.2, the
Development Officer may approve a maximum of two lots, shown on a plan of
subdivision, which are not less than 90% of the required minimums specified in
the Land Use Bylaw, excluding flag lots. Any person requesting a variation shall
submit to the Development Officer an application in the form specified in
Schedule "C".
(b)
Subsection (a) does not apply if the area requirements established by the
Department of the Environment for the construction or installation of an on-site
sewage disposal system are not met.
4.4
Notwithstanding Section 4.1 and the lot area and frontage requirements of Section 4.2,
the Development Officer may approve a subdivision altering the boundaries of two or
more areas of land for the purpose of improving an existing situation, where;
(a)
no additional lots are created;
(b)
the proposed subdivision will not result in any lot having either its lot area or lot
frontage further reduced beyond the minimum requirements of the Land Use
Bylaw.
4.5
Notwithstanding the lot area and frontage requirements of Section 4.2, where a
development component of a permanent nature such as a structure, driveway, well, or on-
site sewage disposal system is encroaching in or upon an immediately adjacent area of
land, the Development Officer may approve a plan of subdivision to the extent necessary
and practical to remove the encroachment.
4.6
Notwithstanding the lot area and frontage requirements of clause 4.2, where a parcel of
land contains more than one main building, the Development Officer may approve a final
plan of subdivision creating the same number of lots or fewer as there are main buildings
provided that each proposed lot is serviced independently by both municipal water and
municipal sanitary sewer and fronts on a public street.
4.7
Wherever possible, side lot lines shall be substantially at right angles to a public street, or
radial to a curved public street.
4.8
Wherever possible, the rear lot lines of a series of adjoining lots shall be continuous, not
stepped or jogged.
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SECTION 5: MUNICIPAL SERVICES AND STREETS
5.1
Where a proposed subdivision involves the construction or extension of a public street or
public water, sanitary sewer, or storm sewer system(s), the subdivider shall construct and
provide such streets and services, free of encumbrances to the Town. Furthermore, the
said streets and services shall comply with the specifications set forth in SCHEDULE "F
Town of Amherst Development Standards" of this Bylaw.
5.2
(a)
All proposed municipal public streets shall be approved by the Town Engineer.
(b)
Where a proposed municipal public street intersects a provincial public street, that
intersection shall be approved by the Town Engineer and the Department of
Transportation and Public Works.
5.3
All proposed accesses to a public street shall be approved by the Development Officer.
5.4
Where a plan of subdivision shows a proposed lot abutting an existing street, the engineer
shall verify that the street is a public street.
5.5
The following are the minimum right-of-way widths for new public streets:
Type of Street
Width
Local
15 m
Cul-de-sac
18.6 m radius
Collector
18 m
Arterial
18 m
5.6
A local public street, unbroken by an intersection shall not exceed 500 metres.
5.7
There shall be no more than four public street approaches in an intersection.
5.8
The minimum distance between public street intersections shall be 60 metres.
5.9
The length of a proposed cul-de-sac shall not exceed 200 meters from an intersection of a
thru street to the base of the turning circle.
5.10
The Development Officer may approve a dead end street in excess of 200 metres in
length, provided it has a temporary turning circle and a second connection to a thru street
is shown on an approved Concept Plan of Subdivision.
5.11
All proposed intersecting streets must intersect at an angle of 70 to 110 degrees for a
minimum distance of 30 meters from the intersection measured from the respective center
lines.
5.12
Where a public street in an adjoining subdivision abuts the boundaries of a plan of
subdivision submitted for approval, the public street in the latter shall, if reasonably
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feasible, be laid out in prolongation of such existing public streets, unless it would be in
violation of this Bylaw.
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SECTION 6: PUBLIC OPEN SPACE
6.1
Prior to approval of the final plan of subdivision by the Development Officer, the
subdivider shall reserve and convey to the Town free of encumbrances, for park,
playground or similar public purposes an area of useable land, as defined below, equal
to 5% of the area of land shown on the final plan of subdivision exclusive of public
streets and the remainder lot.
6.2
The requirements of section 6.2 are waived when the applicant is requesting approval
for:
(a)
the subdivision or consolidation of lots in any zone, other than a residential
zone; or,
(b)
the consolidation or re- subdivision of existing lots where no additional lots are
created, or;
(c)
the consolidation or subdivision of land for which the public land dedication
requirement has already been paid.
6.3
USEABLE LAND for the purpose of this section, means that:
(a)
the land area has a minimum frontage of 6 metres on a public street and an area
that can accommodate a circle with a minimum diameter of 10 metres, except in
the case of a walking or bicycling trail, where the minimum width and street
frontage shall be 3 metres; and,
(b)
in the opinion of the Development Officer and the Director of Operational
Services, can be utilized for passive purposes such as nature trails, picnic sites,
leisure park area, the protection of environmentally significant or sensitive areas
or other public purposes; or,
active purposes such as playing fields, playgrounds, etc., providing that such
acquisition is not premature or inappropriate in terms of the capability of the
Town to absorb any costs relating to the development of the said lands.
6.4
For the purposes of this section "Equivalent Value" shall mean: Payment, in the form of
cash, based on the market value of the newly created lots as determined by an assessor.
6.5
Notwithstanding Section 6.5, where in the opinion of the Development Officer and the
Director of Operational Services, land within the proposed subdivision does not satisfy
the intent of the recreation land acquisition policies of the Municipal Planning Strategy,
the subdivider shall:
(a)
be required to provide equivalent value in the form of cash; or,
(b)
subject to Council approval, provide an equivalent amount of land, or a
combination of equivalent value and land, outside the area being subdivided
which satisfies the intent of the recreation land acquisition policy of the MPS.
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SECTION 7: REQUIREMENTS FOR PRELIMINARY PLANS OF SUBDIVISION
(Subdivider's Optional First Step)
7.1
A subdivider submitting a preliminary plan of subdivision for approval shall submit to the
Development Officer 3 copies of the preliminary plan.
7.2
Preliminary plans shall show the following information:
(a)
the words "Preliminary Plan" located in the title block;
(b)
the "purpose" of the plan described below the title block;
(c)
name of owners of the property being subdivided;
(d)
the civic number of main building(s) on the area of land being subdivided;
(e)
the shape, dimensions, and area of the lots being created or altered;
(f)
each proposed lot identified by a unique number;
(g)
the location of existing and proposed public streets;
(h)
the location of existing buildings within 10 metres of a property line;
(i)
the general location of watercourses and wetlands;
(j)
the north point;
(k)
the scale (in metric);
(l)
any other information necessary to determine if the subdivision meets with
municipal standards and accepted engineering practice as determined by the
Development Officer.
SECTION 5: PROCEDURE FOR APPROVAL OF PRELIMINARY PLANS OF
SUBDIVISION (Optional First Step)
8.1
Application for an evaluation of a preliminary plan shall be made to the Development
Officer in the form specified in Schedule "A" of these regulations.
8.2
The Development Officer shall contact any department of the Town necessary to
determine if the proposed subdivision satisfies the various bylaws and regulations of the
Town.
8.3
The Development Officer shall inform the applicant that he should forward a copy of the
preliminary plan of subdivision to any agency of the Province that the Development
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Officer deems necessary.
8.4
The Development Officer shall inform the subdivider in writing of the results if the
evaluation of the preliminary plan of subdivision.
8.5
The following information shall be stamped or written and completed by the
Development Officer on any preliminary plan which is approved:
(a)
"This preliminary plan is approved. Such approval lapses if the lots are not
shown on a final plan of subdivision approved within one year of the date of the
approval of the preliminary plan."
(b)
the date of the approval of the preliminary plan; and
(c)
"This preliminary plan shall not be filed in the registry of deeds as no subdivision
takes effect until a final plan of subdivision is approved by the Development
Officer and filed in the registry of deeds."
SECTION 9: REQUIREMENTS FOR CONCEPT PLANS OF SUBDIVISION
9.1
Where an area of land is being subdivided in phases and will contain new streets, a
subdivider may submit to the Development Officer a Concept Plan of Subdivision. When
a Concept Plan of Subdivision is submitted the subdivider shall submit ten copies of a
concept plan of the entire area of land at one of the following metric scales - 1:500,
1:1,000 or 1:2,000.
9.2
Concept plans shall have a minimum font size of 2.187 mm and show the following
information:
(a)
the words "Concept Plan" located in the title block;
(b)
the "purpose" of the plan described below the title block;
(c)
name of property owner(s) and name of all abutting landowners;
(d)
the proposed internal street system with connections to existing streets;
(e)
the proposed location of public open space;
(f)
the location of existing development, if any;
(g)
an approximate estimated lot yield figure, based on existing zoning requirements
or requirements of the Department of the Environment and Labour;
(h)
the north point; and
(i)
contours at 2.5 metre intervals;
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(j)
any other information necessary to determine if the subdivision meets with
municipal standards and accepted engineering practice as determined by the
Development Officer.
SECTION 10: PROCEDURE FOR APPROVAL OF CONCEPT PLANS OF
SUBDIVISION
10.1
Application for approval of a concept plan shall be made to the Development Officer in
the form specified in Schedule "A" of these regulations.
10.2
The Development Officer shall comply with the notification and approval provisions of
the Act.
10.3
The Development Officer shall forward the concept plan and any supplementary
information to appropriate agencies in order to evaluate the concept plan in terms of:
(a)
the design's consideration of topography, natural features, and other site
constraints and restrictions;
(b)
street layout, pedestrian routes, and connections with existing and proposed
transportation links on a local and regional scale;
(c)
the feasibility of servicing with applicable services, and the effect of the layout on
the provision of future services where applicable;
(d)
public open space; and
(e)
any proposed community and commercial uses.
10.4
Any agency that has been forwarded a copy of the concept plan pursuant to Section 10.3
shall forward a written report of their assessments or recommendations to the
Development Officer within 7 days of receipt of the said concept plan.
10.5
Approval of a concept plan may not be refused or withheld as a result of the assessment
or recommendations made by the Department of the Environment, the Department of
Transportation and Public Works or of any other agency of the Province or the
municipality unless the concept plan is clearly contrary to a law of the Province or
regulation made pursuant to a law of the Province, including the Town's Municipal
Planning Strategy.
10.6
Where the Development Officer either approves or refuses to approve a concept plan, the
Development Officer shall give notice of the approval or refusal to all agencies that were
forwarded a concept plan pursuant to Section 10.3.
10.7
Where the Development Officer refuses to approve a concept plan, the Development
Officer shall inform the subdivider of the reasons for the refusal in writing and advise the
subdivider of the appeal provisions of Section 284 of the Act.
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10.8
The following information shall be stamped or written by the Development Officer on
any concept plan which is approved:
(a)
"This concept plan is approved. Such approval lapses if the lots are not shown on
a final plan of subdivision approved within five years of the date of the approval
of the concept plan."
(b)
the date of the approval of the concept plan; and
(c)
"This concept plan shall not be filed in the Registry of Deeds as no subdivision
takes effect until a final plan of subdivision is approved by the Development
Officer and filed in the Registry of Deeds."
10.9
The Development Officer shall forward an approved copy of the concept plan to the
subdivider.
SECTION 11: REQUIREMENTS FOR TENTATIVE PLANS OF SUBDIVISION
11.1
A subdivider proposing to subdivide an area of land shall submit to the Development
Officer ten copies of the tentative plan of the proposed subdivision meeting the
requirements of this Section.
11.2 Notwithstanding Section 11.1, the Development Officer may waive the requirement for
the application for tentative plan of subdivision to be submitted where:
(a) the proposed lots abut an existing public street; and,
(b) the proposed lots will be serviced by existing municipal water and sewer services.
11.3
Tentative plans of subdivision submitted to the Development Officer shall be:
(a)
drawn to a scale of either 1:500 or 1:1,000;
(b)
based on a description of the area of land to be subdivided, preferably but
not necessarily as surveyed.
11.4
Tentative plans shall have a minimum font size of 2.187 mm and show the following
information:
(a)
the words "TENTATIVE PLAN OF SUBDIVISION" located above the
title block;
(b)
the "purpose" of the plan described below the title block;
(c)
a clear space for stamping being a minimum of 225 square centimetres
with a minimum width of 8 centimetres;
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(d)
the name of the subdivision, if any, and the name of the owner of the area
of land;
(e)
if applicable, the book and page number of the deed to the area of land as
recorded in the name of the owner in the registry of deeds;
(f)
the unique Parcel Identifier (PID) of all areas of land being subdivided;
(g)
the civic number of main buildings on the area of land being subdivided;
(h)
the names of all owners and the unique Parcel Identifier (PID) of all
properties abutting the proposed subdivision;
(i)
a location map, drawn to a scale not smaller than 1:50,000 (such scale to
be shown on the map), with the same orientation as the area of land
proposed to be subdivided;
(j)
the shape, dimensions, and area of the lots being created;
(k)
each lot being approved identified by a unique number, beginning with the
current calendar year;
(l)
no duplication of lot identifiers;
(m)
the boundaries of lots being created shown by solid lines, and the
vanishing boundaries of existing areas of land being subdivided,
consolidated or both, shown as broken lines;
(n)
the location of existing buildings within 10 metres of a new property
boundary;
(o)
the location of existing and proposed public streets;
(p)
the name of existing and proposed public streets as issued pursuant to the
Town's street naming policy;
(q)
the width and location of railroads and railway rights-of-way;
(r)
the general location of watercourses, wetlands, or prominent rock
formations;
(s)
the width, location, and nature of any easements on or affecting the area of
land proposed to be subdivided;
(t)
where applicable, a notation stating the lots are serviced by a central sewer
and/or water system;
(u)
the north point;
(v)
the date on which the plan of subdivision was drawn and the date of any
revisions;
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(w)
the scale to which the plan of subdivision is drawn; and
(x) any other information necessary to determine whether or not the plan of
subdivision conforms to these regulations.
11.5 Where the tentative plan of subdivision is to be forwarded to the Department of the
Environment the following additional information, if required by the Department of the
Environment, shall be part of, or included with, the tentative plan:
(a)
the lot layout including buildings, proposed on-site sewage disposal
system, proposed driveway and water wells;
(b)
the location of watercourses, wetlands and other features that may
influence the design of the system, including ditches, roads and driveways;
(c)
the surface slopes and directions;
(d)
an explanation of the extent, volume and type of usage to which the
system will be subjected;
(e)
an assessment report of the lot respecting its suitability to support an on-
site sewage disposal system including the results of a soil evaluation test,
except where the assessment report is to be prepared by the Department of
the Environment; and
(f)
any other information necessary to determine whether the subdivision
meets the On-site Sewage Disposal Systems Regulations.
SECTION 12: PROCEDURE FOR APPROVAL OF TENTATIVE PLANS OF
SUBDIVISION
12.1
Application for approval of a tentative plan of subdivision shall be made to the
Development Officer in the form specified in Schedule "A" of these regulations.
12.2
The Development Officer shall comply with the notification and approval provisions of
the Act.
12.3
When applicable the Development Officer shall forward a copy of the tentative plan of
subdivision to:
(a)
in areas not served by a central sewer, the Department of the Environment to
determine compliance with the On-site Sewage Disposal Systems Regulations,
except where the proposed lot:
(i)
is more than 9000 square metres; and ,
(ii)
has a width of 75 metres or more, and
(iii)
is to be used for a purpose that does not require an on-site sewage disposal
16
system;
(b)
the Town Engineer;
(c)
the Manager of Recreation Facilities;
(d)
the authority having jurisdiction for public streets; and
(e)
any other agency of the Province or the municipality that the Development Officer
deems necessary.
12.4
Any agency that has been forwarded a copy of a tentative plan of subdivision pursuant to
Section 12.3 shall forward a written report of their assessments or recommendations to
the Development Officer within 7 days of receipt of the said concept plan.
12.5
Approval of a tentative plan of subdivision may not be refused or withheld as a result of
the assessment or recommendations made by the Department of the Environment, the
Department of Transportation and Public Works or of any other agency of the Province or
the municipality unless the tentative plan of subdivision is clearly contrary to a law of the
Province or regulation made pursuant to a law of the Province, including the Town's
Municipal Planning Strategy.
12.6
Where the Development Officer either approves or refuses to approve a tentative plan of
subdivision, the Development Officer shall give notice of the approval or refusal to all
agencies that were forwarded a plan pursuant to Section 12.3.
12.7
Where the Development Officer refuses to approve a tentative plan of subdivision, the
Development Officer shall inform the subdivider of the reasons for the refusal in writing
and advise the subdivider of the appeal provisions of Section 284 of the Act.
12.8
The following information shall be stamped or written by the Development Officer on
any tentative plan of subdivision which is approved together with any other information,
including conditions, necessary for the tentative plan to proceed to the final plan stage.
(a)
"This tentative plan of subdivision is approved for Lots ___________. Such
approval lapses if the lots are not shown on a final plan of subdivision approved
within two years of the date of the approval of the tentative plan.";
(b)
the date of the approval of the tentative plan; and
(c)
"This tentative plan of subdivision shall not be filed in the Registry of Deeds as no
subdivision takes effect until a final plan of subdivision is approved by the
Development Officer and filed in the Registry of Deeds."
12.9
The Development Officer shall forward a copy of the approved tentative plan of
subdivision to the subdivider and the surveyor.
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SECTION 13: REQUIREMENTS FOR FINAL PLANS OF SUBDIVISION
13.1
A subdivider proposing to subdivide an area of land shall submit ten copies of the final
plan of subdivision meeting the requirements of Section 13.2 of these regulations to the
Development Officer for approval. In addition, a digital copy of the plan shall also be
submitted in one of the following formats: .dwg, .dxf or ESRI format.
13.2
Final plans of subdivision submitted to the Development Officer shall be:
(a)
drawn to a scale of either 1:500 or 1:1,000;
(b)
certified and stamped by a Nova Scotia Land Surveyor that the lots for
which approval is requested and any proposed street and road have been
surveyed in the manner required by the Land Surveyors Act and its
regulations; and
(c)
folded to approximately 20x30 centimetres with the face of the folded
print being the title block that is located in the lower right-hand corner of
the final plan of subdivision.
13.3
Final plans shall have a minimum font size of 2.187 mm and show the following
information::
(a)
the words "PLAN OF SUBDIVISION" located in the title block;
(b)
a clear space for stamping being a minimum of 225 square centimetres
with a minimum width of 8 centimetres;
(c)
the "purpose" of the plan described below the title block;
(d)
the name of the subdivision, if any, and the name of the owner of the area
of land;
(e)
if applicable, the book and page number of the deed to the area of land as
recorded in the name of the owner in the registry of deeds;
(f)
the unique Parcel Identifier (PID) of all areas of land being subdivided;
(g)
the civic number of main buildings on the area of land being subdivided;
(h)
the names of all owners or the identifiers of all properties abutting the
proposed subdivision;
(i)
a location map, drawn to a scale not smaller than 1:50,000 (such scale to
be shown on the map), with the same orientation as the area of land
proposed to be subdivided;
18
(j)
the shape, dimensions, and area of the lots being created;
(k)
each lot being approved identified by a unique number;
(l)
the boundaries of lots being created shown by solid lines, and the
vanishing boundaries of existing areas of land being resubdivided,
consolidated or both, shown as broken lines;
(m)
the location of all buildings within 10 metres of a proposed property
boundary;
(n)
the location of all buildings within 3 metres of an existing boundary;
(o)
the width and location of existing and proposed public streets;
(p)
the name of existing and proposed public streets;
(q)
the width and location of railroads and railway rights-of-way;
(r)
the general location of watercourses, wetlands, or prominent rock
formations;
(s)
the width, location, and nature of any easements on or affecting the area of
land proposed to be subdivided;
(t)
the north point;
(u)
the date on which the plan of subdivision was drawn and the date of any
revisions;
(v)
the scale to which the plan of subdivision is drawn;
(w)
the name, stamp and signature of the surveyor;
(x)
any other information necessary to determine whether or not the plan of
subdivision conforms to this bylaw, and
(y)
where applicable, the Land Registration Act Number (LRA #).
13.4
Where the final plan of subdivision is to be forwarded to the Department of the
Environment the following additional information, if required by the Department of the
Environment, shall be part of, or included with, the final plan:
(a)
the lot layout including buildings, proposed on-site sewage disposal
system, proposed driveway and water wells;
(b)
the location of watercourses, wetlands and other features that may
influence the design of the system, including ditches, roads and driveways;
(c)
the surface slopes and directions;
19
(i) an explanation of the extent, volume and type of usage to
which the system will be subjected;
(e)
an assessment report of the lot respecting its suitability to support an on-
site sewage disposal system including the results of a soil evaluation test,
except where the assessment report is to be prepared by the Department of
the Environment; and
(f)
any other information necessary to determine whether the subdivision
meets the On-site Sewage Disposal Systems Regulations.
SECTION 14: PROCEDURE FOR APPROVAL OF FINAL PLANS OF SUBDIVISION
14.1
Application for approval of a final plan of subdivision shall be made to the Development
Officer in the form specified in Schedule "A" of this bylaw.
14.2
The Development Officer shall comply with the notification and approval provisions of
the Act.
14.3
When applicable the Development Officer shall forward a copy of the final plan of
subdivision to:
(a)
in areas not served by a central sewer, the Department of the Environment to
determine compliance with the On-site Sewage Disposal Systems Regulations;
(b)
the Town Engineer;
(c)
the Manager of Recreation Facilities;
(d)
any other agency of the Province or the Municipality that the Development Officer
deems necessary.
14.4
Any agency that has been forwarded a copy of the final plan of subdivision pursuant to
Section 14.3 shall forward a written report of their assessments or recommendations to
the Development Officer within 7 days of receipt of the said final plan.
14.5
Approval of a final plan of subdivision may not be refused or withheld as a result of the
assessment or recommendations made by the Department of the Environment, the
Department of Transportation and Public Works or of any other agency of the Province or
the municipality unless the final plan of subdivision is clearly contrary to a law of the
Province or regulation made pursuant to a law of the Province, including the Town's
Municipal Planning Strategy.
14.6
At the time of application for approval of a final plan of subdivision, the subdivider shall
submit to the Development Officer:
(a)
the fees for registering the final plan of subdivision, and;
(b)
the fees for filing the notice of subdivision.
20
14.7
Before approving a final plan of subdivision that adds or consolidates parcels or areas of
land in different ownerships, the Development Officer shall have received:
(a)
the executed deeds suitable for registering to effect the addition or consolidation;
(b)
the fees for registering the deeds;
(c)
the affidavit of value including particulars of any exemption, pursuant to Part V of
the Act, including any fees payable
14.8
The Development Officer shall forward an approved copy of the final plan of subdivision
to the subdivider and the surveyor.
14.9
Where the Development Officer either approves or refuses to approve a final plan of
subdivision, the Development Officer shall give notice of the approval or refusal to all
agencies that were forwarded a plan pursuant to Section 14.3.
14.10 Where the Development Officer refuses to approve a final plan of subdivision, the
Development Officer shall inform the subdivider of the reasons for the refusal in writing
and advise the subdivider of the appeal provisions of Section 284 of the Act.
14.11 A final plan of subdivision showing lots to be approved under circumstances described in
subsection 287(3) of the Act, by special note on the plan shall:
(a)
identify such lots;
(b)
state the names of the grantor and the grantee of such lots; and
(c)
state the date, book and page number of the conveyance of such lots as recorded in
the Registry of Deeds.
14.12 The following information shall be stamped or written and completed by the
Development Officer on any final plan of subdivision which is approved:
(a)
"This final plan of subdivision is approved for Lots __________ ";
14.13 The Development Officer shall forward to the registry of deeds:
(a)
Six (6) approved copies of the final plan of subdivision and a notice of approval in
the form specified in Schedule "B" of these regulations; and
(b)
if applicable, the items required by Section 14.7 of this by-law.
21
SECTION 15: REPEAL OF A SUBDIVISION
15.1
Any person requesting a repeal shall submit to the Development Officer an application in
the form specified in Schedule "D".
15.2
The notification and approval provisions of the Act that apply to the approval of a plan
shall also apply to a repeal.
15.3
When the Development Officer is satisfied that an application for repeal is complete, the
Development Officer may forward a copy to any agency which provided an assessment or
recommendations on the original plan of subdivision.
15.4
Where buildings have been erected on the subject lands after the date of the subdivision
approval sought to be repealed, no repeal shall be granted which would cause these
buildings to be in violation of any building code regulations, land-use by-law, or on-site
sewage disposal regulations unless the violation can be rectified by the approval of a new
plan of subdivision filed at the registry of deeds on the same day as the repeal is filed.
15.5
The Development Officer shall forward to the registry of deeds the repeal in the form
specified in Schedule "E".
15.6
The Development Officer shall forward a copy of the repeal to:
(a)
the subdivider, and
(b)
any agency that provided an assessment or recommendations on the original plan
of subdivision.
15.7
At the time of application for the repeal of a subdivision the subdivider shall submit to
the Development Officer:
(a)
the fees contained in the Costs and Fees Act, and its regulations, for registering a
repeal of a plan of subdivision; and,
(b)
Where the Development Officer refuses to repeal a subdivision, the Development
Officer shall return the fees referred to in clause 15.7 (a) to the subdivider.
15.8
Where the Development Officer refuses to repeal a subdivision, the Development Officer
shall give notice of the refusal to all agencies that were forwarded the application for
repeal pursuant to Section 15.3.
22
SCHEDULE "A"
TOWN OF AMHERST
APPLICATION FOR THE APPROVAL OF SUBDIVISION OF LAND
File Reference:
(office use only)
Development Officer:
Type of approval requested:
Tentative
Final
Submitter:
Owner:
Name:
Name:
Address:
Address:
Phone:
Phone:
Fax:
Fax:
Correspondence and approved plan should
be sent to: (please circle)
Submitter
Owner
Other:
Name:
Address:
Phone:
Fax:
Plans Certified by
Approval is requested for the attached plan of subdivision.
The land in question is owned by the undersigned and it is the
intention to subdivide in the manner shown on said plan.
a Nova Scotia Land Surveyor, dated:
Signed:
Please Complete the Following
1. Name of Subdivision:
2. Location of Property:
3. Proposed Lot(s) Identification: (i.e. Lot-1)
4. PID(s) of Affected Parcels:
5. Number of Plans Submitted for approval:
yes
no
n/a
6. Where Applicable, are you prepared to
construct roads to the specifications of the
Town of Amherst?(please circle)
7. Has Deed and affidavit of Value Been Submitted:
yes
no
n/a
(required with two or more owners)
Office Use Only
1. Plan Review Complete:
5. Fees Received:
2. Plan Sent to Reg. for LRA:
6. Plan Approved:
Date:
3. Did Sub. Qualify for LRA?
7. Correspondence Sent:
Date:
4. LRA info Received:
8. Notes:
23
SCHEDULE "B"
NOTICE OF APPROVAL OF A PLAN OF SUBDIVISION IN
ACCORDANCE WITH SUBSECTIONS 285(3) AND 285(4) OF THE MUNICIPAL
GOVERNMENT ACT
Name of Owner(s)
Name of Subdivision
Location
Date of Approval ________________________
For Lot(s)
Surveyor ________________________
Date of Plan
Dated this
day of
Development Officer
______________________, ____
(DATE)
(YEAR)
Plan of Subdivision filed in the registry of deeds as Plan #
Dated this
day of ________________________, 2002.
This plan of subdivision may also contain information regarding the lots
approved on this plan with respect to one or more of the following:
1.
The lots' eligibility for on-site sewage disposal systems.
2.
The availability of central sewer and water systems.
3.
Information indicating whether or not the lots abut a public
street.
24
SCHEDULE "C"
APPLICATION FOR APPROVAL OF LOTS NOT MEETING REQUIREMENTS
This application form should be completed in full and forwarded to the Development Officer for the Town
of Amherst. The applicant is applying under the provisions of Section 4.3 of this Subdivision Bylaw and
Section 279 of the Municipal Government Act, R.S.N.S., 1998, C. 18, as amended for a variance on the
minimum lot dimensions or lot area required by the Land-Use Bylaw and said variance is within the following
guidelines:
1.
The request involves a maximum of two (2) lots.
2.
The lots are/or are not intended to be served by municipal sewer and water services.
3.
The difficulty experienced is not general to the properties in the area or resulting from
the intentional disregard of the requirements of this Subdivision Bylaw.
4.
The proposed lot area and dimensions are no less than ninety percent of the required
minimums for the lot area and dimension.
Name of Property Owner:
Address:
Phone:
Name of Applicant (if not owner):
Address:
Phone:
Location of lot/lots for which a variance is requested:
Lot #1:
Lot #2:
Required
Proposed
Required
Proposed
Area
__________ __________
__________ __________
Lot lines:
Front
__________ __________
__________ __________
R. Side
__________ __________
__________ __________
L. Side
__________ __________
__________ __________
Rear
__________ __________
__________ __________
Why is it not possible to comply with the provisions of this Bylaw?
Has a relaxation ever been applied for on these lots?
YES
NO
If yes, describe briefly:
I certify that I am the owner or am acting with the owner's written consent.
Signature of Applicant
Date
25
SCHEDULE "D"
APPLICATION FOR REPEAL OF A SUBDIVISION
Plan of Subdivision
File Number
APPLICANT RELATED INFORMATION
Name of Land Owner(s) _____________ __________
Phone
Address of Land Owner(s)______________________
Postal Code
Documents To Be Returned To
Correspondence To Be Directed To
INFORMATION RELATED TO THE SUBDIVISION
SOUGHT TO BE REPEALED
Name of applicant for subdivision approval
Location __________________________________ Municipality
The subdivision was approved on the_______day of_________________________ , _________.
(YEAR)
and is filed in the Registry of Deeds at _____________________in the Municipality of
________________________ the County of as #____________
Lot(s) # was/were approved and repeal is
sought for approval of Lot(s) # _____________________________________________________.
Registration fee submitted.
CERTIFICATION OF FACTS
(Reasons For Repeal)
(If more space required, attach additional sheet)
OWNER'S CERTIFICATE
I certify that the information in this application is true and complete, that I am applying for repeal of this
subdivision with the full knowledge and consent of all persons with legal interest, including mortgagees, in the
lands affected by the repeal and that these persons have co-signed this application.
Signature of owner/agent________________________
Date ________________________
Co-Signer
________________________
Date ________________________
26
SCHEDULE "E"
NOTICE OF REPEAL OF A SUBDIVISION
Plan of Subdivision
Name of Owner(s)
Name of Subdivision
Location
Date of Approval of the Subdivision
Being Registration #
at the registry of deeds.
THIS SUBDIVISION IS REPEALED
Entire Plan
or
Only Lots # ________________________
Dated at _______________________________________________________________________
in the Province of Nova Scotia, this _____ day of________________________________, _______.
(DATE)
(YEAR)
Development Officer
Please note: Any lot or parcel created by this repeal may not be eligible for development.
27
SCHEDULE "F"
TOWN OF AMHERST; INFRASTUCTURE DEVELOPMENT STANDARDS
Introduction & Definitions
2
Existing Infrastructure
3
Cost Sharing Policy
3
Developer's Obligation
4
Sanitary Sewer System
7
Sewage Pumping Station
15
Sewage Forcemain Standards
26
Easements
29
Water Distribution System
30
Domestic Water Pumping Station
41
Storm Drainage System
51
Street System
78
28
INTRODUCTION
The intent of this document is to establish the required servicing standards for development in
the Town of Amherst. These standards shall be used in the design and construction of
sanitary and storm sewers, waterworks, and roads, in new developments.
The Developer is responsible for all engineering and will retain the services of a Consulting
Professional Engineer for all engineering which will involve preliminary and final design and
drawings as well as sufficient resident inspection of the works to certify that prior to the Town
taking over the works that the project has been completed to standard. The developer is
responsible to retain and pay for the services of a registered land surveyor where needed.
DEFINITIONS
"Consulting Engineer" shall mean the Engineers appointed by the developer who are
licensed to practice in the Province of Nova Scotia.
"Development" shall mean any change or alteration in the use made of
land including extensions or other modifications to
existing municipal infrastructure as regulated by these
standards.
"Developer" shall mean the owner of an area of land, proposed to be developed, and,
including anyone acting with the Owners written consent.
"Service Laterals" shall mean any service pipe connected to the municipal water, sanitary
sewer or storm water street main.
"Standard Specifications" shall mean the Nova Scotia Standard Specification for Municipal
Services latest edition for construction of the works required for development within the Town
of Amherst.
"Substantial Performance" shall have been reached when the work is ready for use or is
being used for the purpose intended and is so certified by the consulting engineer.
"Total Performance" is defined as the date of one year following the issuance of the
certificate of Substantial Performance which will be the completion of the warranty period.
"Town" shall mean the Town of Amherst, NS.
"Town Engineer" is the Town Engineer or his designate.
"Works" shall mean all required aspects of the development infrastructure required to meet
the Town's standards and any other requirements which may be deemed necessary by the
Town upon review of this particular development
29
EXISTING INFRASTRUCTURE
It is a requirement of the Developer to assess the impact of the development on all existing
infrastructure. This may involve traffic analysis, flow monitoring and pressure testing, or other
investigations as may be described by the Town at the time of the development application.
The Town will be the sole judge of the impact that the development may have on the Town's
infrastructure.
Overloading, damaging or destroying existing infrastructure shall not be permitted. The
developer may be required to upgrade existing infrastructure if it is demonstrated through an
engineering design brief that adverse effects are predicted due to the development. Additions
to existing infrastructure systems shall not cause any adverse effect to or overload of existing
systems.
Where a phased development is being proposed, the developer shall provide a master plan
and design and construct all infrastructure to accommodate full build out of the development.
In addition, infrastructure shall be oversized where required to accommodate future
development on adjacent parcels of land.
COST SHARING POLICY
Certain infrastructure is eligible for cost sharing by the Town when not required to support the proposed
development, including:
-
Sanitary sewer mains exceeding 200 mm in diameter.
-
Water mains exceeding 200 mm in diameter.
-
Storm sewers exceeding 600 mm in diameter.
-
Looping of water mains in cul-de-sacs.
The Town will pay the difference in material costs between the pipe diameters noted above
and the pipe diameters required for the development. If the construction is to be undertaken
by the developer, cost-sharing is contingent upon the following:
-
Formal approval of the Town's portion of the costs by either budget appropriation
or funding authorization.
-
Approval of the plans, specifications and cost-estimate of the work by the Town
before the work commences.
30
DEVELOPER'S OBLIGATIONS
Pre-Construction Obligations:
The developer is responsible for obtaining all approvals for the development in accordance
with all applicable Municipal, Provincial and Federal regulations and specifications including
Town of Amherst and Nova Scotia Department of Environment and Labour.
Design, Construction and Post-Construction Obligations:
1.
Provide construction services through a Professional Engineer with experience in
site development, municipal infrastructure construction and roadway construction
who has been contracted to provide the requirements outlined in this document.
2.
Provide construction drawings and supplementary technical specifications.
3.
Provide and warranty for one year all infrastructure constructed within the
development.
4.
Supply and install electric power and telephone infrastructure on all subdivision
streets per utility and Town requirements.
5.
Provide construction inspection and certification by a Consulting Engineer that all
works have been completed to the relevant Town and Provincial standards.
Certification by the Engineer to be submitted to the Town at the issuance of
Substantial Performance.
6.
Provide record drawings to Town in digital (.dxf) and hardcopy format.
The Contractor/Developer shall ensure that the completed works are protected pending the
Total Performance of the Contract and shall be responsible for the correction of any defects in
the works regardless of whether or not they were apparent when the Certificates of Provisional
or Final Acceptance were issued.
The Consulting Engineer and Town of Amherst shall, upon receipt of an application from the
Contractor/Developer for a Certificate of Substantial Performance, make an inspection and
assessment of the work to verify the validity of the application. When the Engineer finds the
Work to be Substantially Performed a certificate shall be issued. The date of this certificate
shall be the date of Substantial Performance of the Contract.
Immediately following the issuance of the Certificate of Substantial Performance, the Engineer
and the Town of Amherst, in consultation with the Contractor/Developer shall establish a
reasonable date for the Total Performance of the Contract. This will normally be one year
from the date of issuance of the Certificate of Substantial Performance, and will begin the one
year warranty period leading to Total Performance.
The Consulting Engineer and Town of Amherst shall, upon receipt of an application from the
Contractor/Developer for payment upon Total Performance of the Contract, make an
inspection and assessment of the work to verify the validity of the application. The Engineer
shall notify the Contractor of approval or disapproval of the application. When the Engineer
finds the Work to be totally performed satisfactorily a Certificate of Total Performance shall be
issued.
The issuance of the Certificate of Total performance shall constitute a waiver of all claims by the Town
of Amherst against the Contractor/Developer except those previously made in writing and still unsettled,
31
if any, and those arising from the provisions of Warranty, or those arising from negligence on the part of
the Contractor.
Design Brief
Documentation must be provided containing the design rationale and submission
requirements noted in this document for each of the following elements of the subdivision.
- Domestic Water Supply and Fire Protection
- Storm Sewer
- Sanitary Sewer
- Road System
This documentation must be stamped by a Professional Engineer licensed in the Province of
Nova Scotia and be bound into one complete document.
Engineering Design Drawings
All plan and profile drawings and detail drawings shall be presented as follows:
- Each submission to be accompanied by a cover sheet indicating the project title, name
and address of the Developer and the Consulting Engineer.
- Plan and profile tracings shall be top half clear, bottom half ruled. Drawing and
proposed dimensions shall be 600mm x 900mm. All dimensions are to be in metric
units.
- Existing conditions must be shown.
- Plan and profile drawings shall have a horizontal scale of 1:500 and a vertical scale of
1:50.
- North shall point to the top or to the right on all drawings.
- All grading plans and profiles shall be to Geodetic Survey of Canada Datum.
- The zero meterage shall start at the projection of an intersecting street centerline.
- The profile must be a vertical projection of the plan. Intersecting street meterages and
names must be shown on the profile.
- Calculated meterages of the beginning and ends of curves must be noted on the plan
and profile.
- Existing and future services shall be shown on all drawings.
- Each plan shall have the Engineers stamp, signature and date including revision
number.
The following design drawings shall be submitted for review:
- A Cover Sheet shall be provided indicating the following:
o A list of the drawings included in the Contract Set.
o A Key Plan (Scale of 1:50,000) showing the location of the proposed
development.
o The project title and the name and address of the owner and
the Consulting Engineer. A general plan, to a scale of 1:500
showing all services to be constructed.
- Plan and profile drawings with a plan scale of 1:500 showing the existing and proposed
32
finished centerline profile, sanitary sewer system, storm sewer system and water
distribution system.
- A lot grading plan to a scale of 1:1000 showing:
o Estimated final ground elevations at lot corners
o Proposed final centre line of road elevations at 25 metre stations.
o Contours extending a minimum of 25 metres beyond the limit
of the plan at 2.5 meter intervals. N.S. Topographic Records
Database acceptable.
Location and direction of flow of swales by means of arrows with at least one
arrow to be shown at the rear of each lot.
All proposed rear lot catch basins, leads and easements if required.
33
SANITARY SEWER SYSTEM
Developer's Obligations
This section establishes criteria relating to the design and installation of sanitary sewer
systems for new development in the Town of Amherst. All subdivisions or developments
requiring sanitary sewers shall be serviced by connecting sewer lines to the municipal sanitary
sewer system. All plans of such works shall be approved by the Town. These Standards do
not preclude the use of higher standards where required, in the design of infrastructure to
service new development.
Regulatory Standards
Sanitary sewers shall be designed and constructed in accordance with the latest revision of
the Nova Scotia Municipal Services Specification and the Nova Scotia Department of
Environment & Labour for the Installation of Gravity Sewers, Sewage Force mains and Water
Mains in Combined and Separate Trenches. In addition, a copy of the plans must be
submitted to the Provincial Department of Environment & Labour for approval.
A copy of all Regulatory Agency approvals shall be forwarded/copied to the Town before any
work commences.
Contractors/Developers shall make themselves familiar with the requirements of the Nova
Scotia Municipal Services Specification before making application to the Town.
3.1
Scope
anitary sewage is defined as the wastewater from a community consisting of
liquid conveying solids from residential, commercial, and
industrial facilities excluding stormwater inflow and
groundwater infiltration. A sanitary sewerage system is a
system receiving, conveying, and controlling sanitary sewage.
Such systems consist of mainline sewers, lateral sewers, service
lateral lines, pumping facilities, and treatment facilities.
34
3.2
Gravity Systems
3.2.1
Design Requirements
3.2.1.1 General
The sanitary sewerage system shall be designed for peak
flows generated from all lands within the serviceable area
which are naturally tributary to the drainage area as
determined from topographic plans. Any lands within the
serviceable area which are tributary by pumping or
regrading which are at present or anticipated to
contribute to the design area are to be included in the
calculated flows for the system being designed.
3.2.1.2
Materials
Sanitary sewer main material, fittings, and appurtenances
are to be as per the latest version of the Nova Scotia
Standard Specifications for Municipal Services.
Sanitary sewer mains shall be PVC DR-35 colour-coded green
meeting ASTM D 3034 (Latest Edition)
3.2.1.3
Hydraulic Design
Sanitary sewer mains, fittings, and appurtenances shall be
designed to convey the calculated peak design flow (PDF).
The consultant shall ensure that surcharging of the
system does not occur during peak design flow conditions
by taking into consideration the hydraulic gradeline
accounting for factors including backwater effects and
energy losses at manholes.
Peak design flow (PDF) may be calculated by
the following equation:
where:
PDF
peak design flow including extraneous flows (L/s),
P
design population in thousands,
q
average daily domestic flow (L/capday),
M
peaking factor,
I
peak extraneous flow (L/sha)
A
tributary area (ha).
The peaking factor (M) may be calculated by the Harman equation or the Babbit
equation:
[3.2]
A
I
m
q
P
PDF
⋅
+
⋅
⋅
=
4.
86
5.0
4
14
1
P
M
+
+
=
35
[3.3]
The sanitary sewerage system shall be designed for a gross
population density of 45 persons per hectare. Average
daily domestic dry weather flows shall be calculated on
the basis of an allowance of 320 litres per person per
day.
Peak design flows shall be calculated based on an
allowance of 1,430 litres per person per day, plus an
infiltration allowance of 11,230 litres per hectare per
day.
The capacity of the sanitary sewer mains is to be
calculated using the Manning equation or an appropriate
nomograph.
Table presents 3.1 presents a list of Manning roughness coefficients
(n) for various materials.
Table 3.1 - Manning Roughness Coefficient (n) for Piped Flow
Material
Manning
Roughness
Coefficient
(n)
Cast Iron Pipe (Cement Lined)
0.011 to 0.015
Concrete (monolithic)
0.012 to 0.014
Concrete
Reinforced Concrete Pipe (RCP)
0.011 to 0.015
Corrugated Metal Pipe (plain)
0.022 to 0.026
Corrugated Metal Pipe (paved invert)
0.018 to 0.022
Corrugated
Steel
Pipe
Corrugated Metal Pipe (spun asphalt
lined)
0.011 to 0.015
Ribbed
Plain
0.011 to 0.015
Plastic Pipe
PVC/HDPE
3.2.1.4
Minimum Velocity
Under peak design flow (PDF) conditions from the tributary
area, when fully developed, sanitary sewage flow
velocities shall be a minimum of 0.6 m/s.
3.2.1.5
Maximum Velocity
Under peak design flow (PDF) conditions from the tributary
area, when fully developed, sanitary sewage flow
velocities shall be a maximum of 4.0 m/s.
2.0
5
P
M =
36
3.2.1.6
Minimum Diameter
Sanitary sewer main diameter shall not be less than 200 mm
in diameter.
3.2.1.7
Changes in Diameter
Sanitary sewer main diameter shall not decrease in the
downstream direction. Manholes are to be provided where
the sanitary sewer main diameter changes.
3.2.1.8
Minimum Slope
The minimum pipe slope for sanitary sewerage mains is
0.4%. The minimum slope for sanitary sewerage mains on a
permanent dead-end is 0.6%. Under special conditions, if
full and justifiable reasons are given, slopes less than
0.4% and 0.6% may be permitted provided that self-
cleansing velocities under full flow conditions are
maintained. Minimum pipe slopes required to produce a
self-cleansing velocity for full flow conditions of 0.6
m/s are presented in Table 3.2. Such decreased slopes
will only be considered where the depth of flow will be at
least 30 percent of the diameter of the pipe for Peak
Design Flow. The slope shall be selected to obtain the
greatest practical velocities to minimize settling
problems. In no case shall the slope be reduced to less
than 0.10 percent.
37
Table 3.2 - Minimum Slope for Sanitary Sewers Possessing Self-
Cleansing
Velocities Under Full-Flow Conditions
Sanitary Sewer Main Diameter
(mm)
Minimum Slope
(m/m)
200
0.40
250
0.28
300
0.22
350
0.17
375
0.15
400
0.14
450
0.12
525
0.10
600
0.1
675
0.1
750
0.1
900
0.1
3.2.1.9
Minimum Depth
The design engineer shall take into consideration possible
future extensions of the gravity sanitary sewer system
when determining depth of cover and grade of sewer mains
so that, wherever possible, those mains shall be installed
at a sufficient depth to provide service to adjoining
lands.
The depth of sanitary sewer mains as measured from the
design grade at finished surface to the crown of the pipe
shall be a minimum of 1.5 m. The depth of sanitary
service laterals at the property line measured from
finished surface to crown of pipe shall be a minimum of
1.5 m.
The sanitary sewer depth shall be sufficient to service
the proposed basement elevations and to avoid conflicts
with other underground utilities.
3.2.1.10 Location
Wherever possible, all sanitary sewer mains and
appurtenances shall be located within the street right-of-
way or a right-of-way owned by the Town of Amherst.
The minimum width of an easement shall be 6.0 m. However,
the actual width shall depend upon the depth and size of
any pipe contained therein such that safe access to the
pipe is possible. Easements shall be of sufficient width
to allow safe access to the pipe line in accordance with
38
the requirements of the Occupational Health and Safety Act
for the Province of Nova Scotia. All sanitary sewer mains
shall be located as close as possible to the centreline of
the street or right-of-way.
Where a need is identified by the Town of Amherst to
accommodate future upstream lands naturally tributary to
the drainage area, an easement shall be provided from the
edge of a street right-of-way to the upstream limit of the
subdivision at a location to be approved by the Town
Engineer.
3.2.1.11 Manholes
Sanitary sewer manholes are to be as per the latest
version of the Nova Scotia Standard Specifications for
Municipal Services.
A manhole is to be provided on a sanitary sewer main at
any change in diameter, material, horizontal alignment,
vertical alignment, at pipe main intersections, and at the
upstream end of each line. Where a sanitary sewer main is
less than 600mm in diameter, manhole spacing shall not
exceed 100m.
The following criteria shall be used for pipe elevation
and alignment in sanitary sewer manholes to account for
hydraulic losses through the manhole:
-
An invert drop equal to those presented in Table 3.3
shall be provided unless a different drop is determined
by appropriate calculations.
39
Table 3.3 - Minimum Manhole Drops for Sanitary Sewers
Manhole Deflection
Minimum Manhole Drop
(mm)
Straight Run
15
Deflection up to 45o
30
Deflection up to 90o
60
-
The crown of a downstream pipe shall not be higher than
the crown of an upstream pipe.
-
At the connection of a lateral sewer to a mainline sewer,
300 mm in diameter or larger, the lateral sewer invert
shall be no lower than the 0.75 D point of the mainline
sewer, as measured from the invert of the mainline sewer.
-
An internal/external drop manhole shall be constructed
where the vertical drop between pipe inverts in the
manhole exceeds 1.0 m.
The design engineer shall take into consideration energy
losses at manholes during peak design flow (PDF)
conditions to ensure that surcharging of the system does
not occur.
The minimum internal diameter of a manhole shall be 1050
mm. The design engineer shall ensure that the internal
diameter is adequate to accommodate all pipe and
appurtenances in accordance with manufacturer's
recommendations.
3.2.1.12 Service Laterals
All sanitary service laterals, fittings, and appurtenances
are to be as per the latest version of the Nova Scotia
Standard Specifications for Municipal Services.
All service laterals shall be installed according to the
following provisions:
-
Each property will be provided with sewer lateral
connection of a minimum diameter of 100 mm, having a
minimum slope of 1.5% from the main to the property line.
40
-
A "tee connection" or saddle must be provided at the main
for the sanitary sewer service lateral.
-
Where existing isolated buildings become part of a
subdivision, their sewers shall be connected to the new
system.
-
Storm service lateral locations will be subject to the
approval of the Town Engineer. Where the lot slopes
along the frontage, the service lateral must be installed
at the down grade corner of the lot.
-
Sanitary service laterals 200 mm or greater must connect
to the sewer main at a manhole structure.
-
All properties shall have a back water valve installed on
the sanitary sewer service line located within the
building limits or, at the Towns discretion, outside the
building limits.
-
For semi-detached buildings, one sanitary service lateral
is required for each dwelling.
-
The depth of sanitary service laterals shall not be less
than 1.5 m within the street right-of-way.
-
Sanitary service laterals with a total length greater
than 25 m shall be installed complete with a wye-type
cleanout or access manhole in a location as approved by
the Town of Amherst.
-
Sanitary Sewer Service laterals shall be PVC DR-35 color
coded green meeting STM D 3034, latest edition.
3.2.1.13 Groundwater Migration
The design engineer shall assess the possibility of
groundwater migration through mainline, lateral, and
service lateral trenches resulting from the use of
pervious bedding material. Corrective measures, including
provision of impermeable collars or plugs, to reduce the
potential for basement and street flooding resulting from
groundwater migration should be employed.
3.2.1.14 Video Inspection
All sanitary sewer mains and lateral services between the
main and property line shall be video inspected to ensure
the integrity of the pipe installation. Video tape
recording and inspection report including index of this
inspection will be turned over to the Town Engineer before
the final inspection of the municipal services.
3.3
Sewage Pumping Station
3.3.1
Design Requirements
3.3.1.1 General
Pumping stations shall be provided when, in the opinion of
the Town of Amherst, a gravity system is either not
possible or not economically feasible.
41
3.3.1.2 Flooding
Sewage pumping stations and appurtenances should be
protected from flooding and flood related damage by the 1
in 100 year storm.
Sewage pumping stations and appurtenances should remain
operational during the 1 in 25 year storm.
3.3.1.3 Surcharge
Pumping stations are to be designed such that the incoming
sewers will not surcharge under peak flow conditions.
3.3.1.4
Access
Town approved access hatchways and doorways shall be
provided. All locks shall be keyed alike to the Town of
Amherst standard.
3.3.1.5 Equipment Removal
All pumping stations shall be equipped with Town approved
devices for the removal and maintenance of pumps, motors,
controls, and auxiliary power equipment.
3.3.1.6 Design Capacity
Unless otherwise approved by the Town of Amherst, all
pumping stations, including wet wells, dry wells, pumps,
forcemains and appurtenances shall be designed for the
ultimate sanitary sewage flows from the tributary drainage
area as described in Section 3.2.1. In the selection of
pumps, both present and ultimate development conditions
shall be considered, and pump overloading situations
avoided.
Design parameters such as the Hazen Williams roughness
coefficient (Chw) of pipe and flow volumes can vary
significantly over time, and therefore pumps must be
designed for the maximum ultimate flow.
3.3.1.7 Phased Development
In situations of phased development, the effects of
minimum flow conditions shall be investigated to ensure
that the retention time in the wet well will not create an
odour or septic problem, and that pumping equipment will
not operate too infrequently based on manufacturer's
recommendations. Pump operational floats and wet well
levels should be adjusted to account for phased
development.
42
3.3.1.8 Safety Precautions
The pumping station and appurtenances shall be designed in
such a manner as to ensure the safety of operations, in
accordance with all applicable Municipal, Provincial, and
Federal regulations including the Occupational Health &
Safety Act of the Province of Nova Scotia. All moving
equipment shall be covered with suitable guards to prevent
accidental contact.
Equipment that automatically starts and stops shall be
suitably signed to ensure that operators are aware of this
condition. Lock-outs on all equipment shall be provided
to ensure that the equipment is completely out of service
when maintenance or servicing is being conducted.
3.3.2
Pumping Requirements
3.3.2.1
Pump Selection
Pumps are to be selected to perform at maximum efficiency under
normal operating conditions.
System head calculations and curves shall be provided for the
range of operating conditions and roughness coefficients
presented in Table 3.4.
43
Table 3.4 - Sanitary Sewage Pump Selection Criteria
Operating
Conditio
n
Roughness
Coefficient
(Chw)
Wet Well
Sewage Level
A
110
Low sewage level in initial condition
B
120
Medium sewage level over normal operating
range
C
130
High sewage level in overflow condition
Operative curves for condition 'b' shall be used to select the
pump and motor since this most closely represents normal
operating conditions. The extreme operating ranges will
be given by the intersections of condition 'a' and
condition 'c' with the selected pump curve. The pump and
motor shall be capable of operating satisfactorily over
the full range of operating conditions.
3.3.2.2 Duplicate Pumps
All pumping stations must have a minimum of two pumping
assemblies. If only two pumps are provided, they shall
each have the same capacity, with each pump capable of
handling the expected Peak Design Flow. Where three or
more units are provided, they shall be designed to fit
actual flow conditions and must be of such capacity that,
with any one unit out of service, the remaining units will
have capacity to handle Peak Design Flow, taking into
account head losses associated with parallel pump
operation.
The pump control circuitry shall be designed to automatically
alternate pumps for each pumping cycle. Run time meters
shall be provided for each pump, and an additional meter
shall be provided to record run time for two pumps
operating simultaneously.
3.3.2.3 Pump Intake
Each pump should have an individual intake located in the wet well to minimize
turbulent flow conditions.
3.3.2.4 Positive Suction Head
Pumping stations, wet wells, and dry wells, are to be designed
such that all pumps will operate under a continuous
positive suction head condition during the entire pump
cycle.
3.3.2.5 Minimum Velocity/Maximum Velocity
44
Suction and header piping shall be sized to carry the Peak
Design Flow of the maximum permissible discharge rate.
Flow velocities shall be:
-
Minimum self-cleansing velocity of 0.6 m/s
-
Maximum velocity of 1.5 m/s
Regardless of the above conditions, piping less than 100 mm in
diameter is not acceptable, unless otherwise approved by
the Town of Amherst.
3.3.2.6 Mechanical Piping
All mechanical piping including suction and header piping shall
be either ductile iron, Class 54 with coal tar epoxy
lining or stainless steel, Type 316 or 316L, 11 Gauge.
Regular steel pipe spool pieces are not permitted.
Threaded flanges shall be used for all ductile iron pipe
joints, fittings, and connections within the station.
Pressed or rolled vanstone neck flanges shall be used for
all stainless steel pipe joints, fittings, and
connections. All piping within the pumping station shall
be properly supported and shall be designed with
appropriate fittings to allow for expansion, contraction,
and thrust restraint.
3.3.2.7 Valves
Hand operated isolation valves must be provided on discharge
and/or suction piping to allow for proper maintenance. A
check valve shall be provided on the discharge lines
between the isolation valve and the pump. Check valves
shall be accessible for maintenance.
All valves and other appurtenances must be located outside the
wet well and installed so that they can be operated under
normal conditions.
3.3.2.8 Pump Openings
All pump openings shall be capable of passing spheres a minimum
of 75 mm in diameter. All pump inlet and discharge
openings shall be a minimum of 100 mm in diameter.
3.3.2.9
Pump Removal
All pumps shall be removable for maintenance and repair.
All submersible pumps shall be removable for maintenance and
45
repair without dewatering the wet well.
All submersible pumps shall be equipped with remote release
mechanisms, guide tracks, lift rings, cables, hoisting
equipment and appurtenances.
3.3.2.10 Submersible Pump Flush Valve
Submersible pumps are to be designed to minimize the deposition
of solids in the wet well. One flush valve per wet well
is to be provided on all submersible pump installations.
3.3.2.11 Hydraulic Analysis
A hydraulic transient analysis shall be undertaken to ensure
that pressure surges resulting from pump start, stop, and
full load rejection during power failure do not adversely
affect the mechanical piping or valves in the system.
3.3.3
Power Supply
3.3.3.1 Electrical
All electrical equipment and appurtenances installed within
partially enclosed, or fully enclosed spaces that may be
subjected to the presence of flammable or explosive
materials shall comply with Part 1 of the Canadian
Electrical Code.
-
Electric motors less than 10 h.p. shall be 208 v, 3-
phase.
-
Electric motors 10 h.p. and larger shall be 600 v, 3-
phase, and VFD controlled.
In instances where only single-phase power is available,
electric pump motors must be supplied to suit this
condition.
3.3.3.2 Control Panel
All pumping station control equipment is to be mounted in
either a CSA Type 3 stainless steel enclosure, or a
Surflex Model 215, or an approved equal. Each panel is to
be equipped with a Surfline Model 9015 pump controller
complete with communications hardware, including all
connections made to phone data lines and interface cables.
46
Communication software shall be provided and must be fully
compatible with the Town of Amherst's SCADA central
monitoring system.
Adequate grounding of all electrical equipment and
appurtenances and lighting arrestors shall be provided.
The control panel is to be isolated from the wet well by a
conduit seal meeting the requirements of Part 1 of the
Canadian Electrical Code.
3.3.3.3 Power Cord
The pump motor power cord shall be designed for flexibility and
serviceability for use in a wet and corrosive environment.
The pump motor power cord shall be equipped with ground
fault protection and meet all requirements of Part 1 of
the Canadian Electrical
Code.
3.3.3.4 SCADA System
The SCADA unit must be compatible with the system presently in
use in the Town of Amherst. The SCADA unit shall have two
extra digital points and two extra analog points and shall
be capable of transmitting the following signals and
alarms to the central monitoring location:
Electrical service from the transmission main to the control
panel and the data transmission wiring from the station
SCADA output to the telephone system shall be placed
through buried conduit.
Pumping station functions must be monitored using an integrated Supervisory
Control and Data Acquisition (SCADA) system to ensure that the station is
performing satisfactorily. All software is to be fully compatible with the Town of
Amherst central SCADA system. The SCADA unit must have two extra digital
points and two extra analog points and must be capable of transmitting the
following signals and alarms to the central monitoring location:
A flow meter, approved by the Town Engineer, must be installed in the pumping
station. Town approved pressure gauges, complete with isolation valves, must
be installed on the suction side and on the discharge side of the pumps.
Pumping Stations shall be equipped with alarm systems that will activate and
send a signal for the following conditions:
Alarm Conditions
47
-
Hand-off automatic selector switch status
-
Output control thought SCADA system
-
Power generating system (overload, battery status, fuel tank level, etc.)
-
Low level alarm
-
High level alarm
-
Intrusion alarm
-
Building fire alarm
-
Power failure alarm
-
Panic alarm
-
Low and or High temperature alarm
-
Pump information alarms (overload, underload, leakage, motor current, pump
status and phase monitoring)
-
Building flood alarm
Station Operating Data
-
Station voltage
-
Amperages
-
Station metered discharge
-
Pump status (On/Off)
Standby Power Unit Alarms (If applicable)
-
Power failure alarm
-
Generator status (On/Off)
-
Hand-off automatic selector switch status (On/Off)
-
Battery status (Charged/Charging)
-
Fuel tank level (Diesel only)
-
Fuel tank pressure (Propane only)
-
Generator current overload alarm
-
Generator temperature overload alarm
3.3.4
Wet Wells
3.3.4.1 Pump Cycle
The wet well should be sized in order to provide a minimum of a 10 min. cycle
time for each pump. For a two pump sewage pumping station, the wet well
should be sized in order to provide a volume (m3) of 0.15 times the maximum
pumping rate (l/s) of one pump for one pump cycle.
3.3.4.2 Float Controls
All pumping stations shall have either pressure transducer
controls, mechanical float controls (Flygt ENM-10 or
equivalent mechanical switches) or ultrasonic echo
controls set to control pump starts and stops. Additional
48
controls shall be provided for high level alarm and low
level alarm.
3.3.4.3 Pump Start Elevation
The wet well level required for pump start should be a minimum
of 300 mm below the invert of the inlet pipe to the wet
well. However, under special conditions, if full and
justifiable reasons are given, the wet well level required
for pump start may be permitted above the invert of the
inlet pipe provided that surcharging of the gravity
system, basement flooding, and solids deposition do not
occur.
3.3.4.4 Pump Stop Elevation
The wet well level required for pump stop should be a minimum
of 300 mm, or two times the pump inlet pipe diameter above
the centreline of the pump inlet pipe.
3.3.4.5 Sump Elevation
The wet well sump should be a minimum of D/3 and a maximum of
D/2 below the intake of bell-mouth and turned-down pump
inlets where D is the diameter of the pump inlet.
3.3.4.6 Emergency Overflow
Although every sewage pumping station is designed to minimize
or eliminate the occurrence of overflows by the provision
of redundant pumping systems, underground storage, and
auxiliary power, each pumping station shall be provided
with an emergency overflow arrangement acceptable to both
the Town of Amherst and Nova Scotia Department of
Environment and Labour.
The invert of the emergency overflow pipe at the pumping
station shall be lower than the invert of any sanitary
sewer laterals at the property line. The invert of the
emergency overflow pipe shall be at an elevation high
enough to prevent backwater effects or surcharging of the
sanitary sewerage system due to elevated hydraulic
gradelines in the receiving system.
In addition, to prevent or minimize emergency overflows, each
pumping station shall be designed with a detention
49
capacity calculated on the basis of Peak Design Flow for a
duration related to frequency and length of power outages
based on historical records for the area.
In the absence of reliable historical records regarding the
frequency and length of power outages, a minimum detention
capacity of 4.5 hours at Peak Design Flow shall be
provided. An auxiliary power supply may be used as a
substitute for detention capacity at the pumping station.
3.3.4.7
Auxiliary Power
The auxiliary power supply shall be designed with adequate
capacity to start and operate the sewage pumps required to
pump Peak Design Flows, control and monitoring systems,
and heating and lighting systems within the pump house.
3.3.4.8 Auxiliary Power Building
A building shall be provided to house the auxiliary power
supply unit, control panel, piping, valves, and any other
appurtenances. These items shall be located in the
building in such a way as to provide convenient access and
safety of maintenance personnel.
The auxiliary power supply building construction shall meet the
requirements of all applicable Municipal, Provincial, and
Federal regulations, including the latest edition of the
National Building Code of Canada, and the latest edition
of the Canadian Electrical Code.
Exterior wall assembly shall be 200 mm (8 inch) split face
concrete block with a minimum of R-10 insulation.
The building shall have a hip roof with a minimum slope of 12
horizontal to 6 vertical and a minimum of R-20 insulation.
There shall be no windows in any exterior wall. Adequate
ventilation for all mechanical equipment shall be provided
by vandal-resistant, heavy duty type steel intake and
exhaust louvres. Engine emissions shall be directed away
from the building so as not to create a ventilation "short
circuit". Provision shall be made to support wall mounted
equipment inside the building.
The building floor shall be a minimum 150 mm above the external
ground surface. The sewage pumping station shall
accommodate the flooding criteria of Section 3.3.1.2.
Pump house floors shall be poured reinforced concrete and
sloped toward the access door, or be designed with a floor
drain system.
50
All interior wall surfaces, doors, and trim shall be painted to
a colour scheme as approved by the Town of Amherst.
3.3.4.9 Floor Slope
The wet well floor slope to the hopper bottom shall be a
minimum of 1:1 (H:V). The area of the hopper bottom shall
be no greater than necessary to accommodate the
installation and operation of the pump inlets.
3.3.4.10 Wet Well Ventilation
Adequate ventilation shall be provided for all sewage pumping
stations. Mechanical ventilation is required for all
buried installations, including wet wells, dry wells, pump
pits, and valve chambers. Wet wells and dry wells shall
have independent ventilation systems with no
interconnection between the systems. For buried
installations greater than 4.5 m in depth, multiple
ventilation inlets and outlets are recommended.
For submersible pump installations, an adequate ventilation
system capable of delivering fresh air to the wet well at
a rate of 110 litres per second at 15 mm static pressure
is to be provided (acceptable model - Joy 4076, 115, 1/12
HP, or equivalent). A separate circuit is to be provided
for the fan with ground fault interrupter. The
ventilation fan is to be controlled by a switch at the
pumping station control panel set to operate when the
control panel door is opened. The ventilation fan
controls shall also provide for automatic operation of the
fan at least 4 times during a 24 hour period. The
ventilation fan is to be mounted on the pumping station
control panel mounting structure adjacent to the control
panel.
3.3.4.11 Inlet Arrangement
A manhole shall be provided outside of the pumping station to
collect the flow from all contributing sanitary sewer
mains. Only one inlet pipe shall be permitted from this
collection manhole to the pumping station wet well.
Discharge to the wet well must be controlled to prevent
turbulence and flood interference.
51
.3.4.12 Access
Vehicle access to the sewage pumping station shall be provided in order
to accommodate the need for maintenance and service
personnel and vehicles.
Driveway of 3.4m minimum width shall be provided. The driveway shall be
constructed of 300 mm thick crushed stone.
Town approved access hatchways and doorways shall be provided. All locks
shall be keyed alike to the Town of Amherst standard with
keys provided to the Town.
3.3.5
Site Considerations
All pumping stations and control panels shall be located off the street right-of-way
in an appropriate area specifically designated for that purpose. The ownership of
this property shall be deeded to the Town. All pumping station land shall be
graded such that ponding of water does not occur. The elevation of the top of
the wet well shall be no less than 100 mm and no more than 150 mm above the
finished grade of the pumping station lot. All exposed areas shall be
sodded/hydroseeded.
3.3.6
Operation and Maintenance Manual
Three (3) copies of the pumping station operation and maintenance manual must
be prepared in a form acceptable to the Town of Amherst, and provided to the
Town of Amherst prior to acceptance of the pumping station. This manual must
contain at least the following:
-
System description
-
Design parameters, system hydraulics, design calculations, and system
curves
-
Civil, mechanical, and electrical drawings, record drawings
-
Pump literature, pump curves, and operating instructions
-
Manufacturer's operation and maintenance instructions for all equipment
-
Name, address, and telephone number of all equipment suppliers and
installers
-
Information on guarantees/warranties for all equipment
All special tools and standard spare parts for all pumping station equipment is to
be provided by the contractor prior to acceptance of the system by the Town of
Amherst.
3.4
Forcemain Standards
3.4.1
Sanitary Forcemain
52
The following types of pipe are approved for use for all sanitary sewer forcemains
in the Town of Amherst. Also included in this listing are conditions or
requirements which are to be met where each type of pipe is proposed for use.
-
Ductile Iron Pipe, Class 52, cement lined is generally
accepted for use in any buried forcemain application in
the Town of Amherst. However, the design engineer shall
carry out an investigation of soil conditions to
determine requirements for an appropriate means of
corrosion protection.
-
Ductile Iron Pipe, Class 350, cement lined may be used in
certain applications. This pipe is approved for use in
sizes up to and including 250 mm diameter. All Class 350
ductile iron pipe is to be installed with polyethylene
encasement and all fittings are to be wrapped with an
approved anti-corrosion tape such as "Denso" or approved
equal.
-
PVC Pipe, DR18 may be used in certain applications. This
pipe is approved for use in sizes up to and including 250
mm diameter. All fittings used with PVC pipe
installations are to be wrapped with an approved anti-
corrosion tape such as "Denso" or approved equal.
3.4.2
Design Friction Loss
The hydraulic losses in the forcemain shall be calculated using the Hazen-
Williams formula or an appropriate nomograph. Hazen-Williams roughness
coefficients (Chw) are presented in Table 3.3.
3.4.3
Identification
Since forcemains are constructed of material which could cause that pipeline to
be confused with a potable watermain, the forcemain shall be identified by
placing an underground warning tape at the top of the primary backfill layer
above the pipe. The warning tape shall be 150 mm wide polyethylene tape with
green background and black lettering. The message on the warning tape shall
be "Caution, Sewer Line Buried".
3.4.4
Minimum Velocity/Maximum Velocity
The forcemain shall be designed such that a minimum cleansing velocity of 0.6
m/s is maintained for Peak Design Flow conditions.
The maximum velocity in any forcemain shall not exceed 2.4 m/s with two or
more pumps operating or 1.5 m/s with one pump operating. Piping less than 100
mm in diameter is not acceptable, unless otherwise approved by the Town of
Amherst.
3.4.5
Minimum Depth/Maximum Depth
53
Forcemains shall have a minimum cover of 1.5 m
Forcemains shall have a maximum cover of 2.4 m. The depth of cover shall be
that as measured from the design grade at finished surface to the crown of the
pipe line.
3.4.6
Minimum Horizontal Separation/Maximum Vertical Separation
Forcemains shall not be located in common trench with a watermain. There
shall be a 3.0 m horizontal separation between forcemains and watermains.
There shall be a 0.5 m vertical separation between forcemains and watermains.
At crossing locations, one full length of watermain will be laid so that the joints
are located equidistant from the forcemain.
3.4.7
Valves
To prevent air locks in the pipe, automatic air relief and vacuum valves shall be
located in a manhole at all high points of the forcemain system or in such other
locations as directed by the Engineer. Drain valves shall be located at low points
as required by the Engineer.
3.4.8
Change in Direction
Any change in direction which is in excess of the pipe joint deflection tolerance
shall require a suitable fitting as approved by the Town of Amherst. Thrust blocks
and mechanical restraining glands shall be provided at any change of direction
and shall be designed considering the operating pressure, surge pressure, peak
flow velocity, and the bearing capacity of the trench floor and wall.
3.4.9
Termination
Forcemains shall terminate in a well-benched manhole such that the flow is
directed down the barrel of the receiving gravity pipe. The downstream pipe
receiving flow from a forcemain must be of sufficient size and grade to prevent
surcharging at the maximum flow from the forcemain.
54
SUBDIVISION DESIGN GUIDELINES - Easements
4.1
General
4.1.1 Easement means an incorporeal right, distinct from ownership of the soil, vested in the
Town and consisting of a use of another's land for any Public service or utility.
4.1.2 When sewers, surface drainage or water system pipes are to be installed other than in
a street or walkway, an easement shall be provided over such installations.
4.1.3 The owner of the easement land shall not construct any type of structure over such
easement area.
4.2
Design
4.2.1 The width of any easement shall be based upon the type, depth and number of services
proposed to be installed.
4.2.2 The minimum width of an easement shall be six meters.
4.2.3 The alignments for any easement shall be dependent upon the type of service to be
installed.
55
WATER DISTRIBUTION SYSTEM
DEVELOPER'S OBLIGATIONS
This section establishes criteria relating to the design and installation of water distribution systems
for new development served by the Town of Amherst Water Utility. These Guidelines do not
preclude the use of higher standards, where required in the design of infrastructure to service new
development. No water will be supplied to any development unless servicing was installed in
accordance with these Town Standards and the Amherst Water Utility Regulations.
REGULATORY AGENCY'S AND STANDARDS
AWWA and CSA Standards
Fire Underwriters Guidelines
Canadian Plumbing Code
Nova Scotia Standard Municipal Services Specification
Nova Scotia Department of Environment and Labor
A copy of all Regulatory Agency approvals shall be forwarded/copied to the Town before any work
commences.
Contractors/Developers shall make themselves familiar with the requirements of the Nova Scotia
Municipal Services Specification before making application to the Town.
DESIGN CRITERIA AND STANDARDS
5.1
Scope
A water distribution system is a system, conveying, and controlling potable water.
Such systems consist of mainlines, lateral lines, fittings and appurtenances,
pumping facilities, treatment facilities, pressure control facilities, and storage
facilities. Water supply and water quality is monitored and maintained by the Town
of Amherst Operational Services Department and water distribution systems must be
designed such that the water quality is maintained while being distributed at adequate
flows and pressures.
In addition to these design criteria, all water distributions systems must conform to the
latest edition of the Standard Specification for Municipal Services for Nova Scotia, and
the following:
-
Water Supply for Public Fire Protection - A Guide to Recommended Practice as
prepared by the Fire Underwriter's Survey (FUS) in conjunction with the Insurers'
Advisory Organisation (IAO)
-
National Fire Protection Association (NFPA)
-
American Water Works Association (AWWA)
-
Hydraulic Institute Standards (HIS)
-
Canadian Standards Association (CSA)
-
National Building Code (NBC)
-
National Plumbing Code (NPC)
-
Underwriters Laboratories of Canada (ULC)
56
Additionally, water distribution systems must conform to any requirements established by
the Nova Scotia Department of Environment and Labour (NSDEL). No system shall be
constructed until the design has been approved by the Town Engineer and NSDEL.
5.2
System Design
5.2.1
Design Water Demands
Water distribution systems must be designed to accommodate
the greater of either of the following demands:
-
Maximum Daily Demand plus Fire Flow (where Fire Flow is
to be provided);
-
Maximum Hourly Demand;
unless otherwise approved by the Town Engineer.
Fire Flow demand must be established by the Town Engineer in accordance
with the latest requirements contained in the publication
Water Supply for Public Fire Protection - A Guide to
Recommended Practice, as prepared by the Fire
Underwriter's Survey (FUS) in conjunction with the
Insurers' Advisory Organisation (IAO).
Domestic flow demands must be established in accordance with the
following:
-
Average Daily Demand:
300 litres per capita per day;
-
Maximum Daily Demand:
600 litres per capita per day;
-
Maximum Hourly Demand:
1,000 litres per capita per day.
Domestic flow demands must be based upon a gross population density of 45
persons per hectare. In developments where the
anticipated population exceeds, or is anticipated to
exceed, the population density of 45 persons per hectare,
or in areas of commercial, industrial, or institutional
development, the domestic demand shall be adjusted
accordingly. Typical water demands for commercial,
industrial, and institutional development are presented in
Table 5.1.
Table 5.1
Typical Water Demands for Commercial, Industrial, and Institutional Development
Development
Water Demand
Unit
Shopping Centre
2,500 - 5,000
L / 1,000m2 / day
57
Hospital
900 - 1,800
L / bed / day
School
70 - 140
L / student / day
Recreational Vehicle Park - without
hook-ups
340
L/ site / day
Recreational Vehicle Park - with hook-
ups
800
L / site / day
Campground
225 - 570
L / site / day
Manufactured Home Park
1,000
L / site / day
Motel
150 - 200
L / bed space /
day
Hotel
225
L / bed space /
day
5.2.2
Minimum Pressures
Water distribution systems must be designed and sized in order to provide
and maintain a minimum residual pressure of 200 kPa,
measured at the main, at all points along the distribution
system during Maximum Hourly Demand conditions. Water
distribution systems must be designed and sized in order
to provide and maintain a minimum residual pressure of 150
kPa at all points along the distribution system during
Maximum Daily Demand plus Fire Flow conditions.
Design calculations and analysis are to be submitted by the Consultant in
the form of a Design Brief at the time that the
Application for Final Approval for the extension of, or
connection to, an existing water distribution system is
made.
As a result of differences in ground elevations, or distance from the
source of supply, isolated areas may require increasing
the pressure of the water system to adequately meet
minimum pressure requirements. In order to accomplish
this, a water booster station may be required to
adequately service a specific area. Such areas, or
Pressure Zones, are generally isolated from the remainder
of the water distribution system.
In the event that the number of dwellings or structures affected by
inadequate domestic flow and pressure within a Pressure
Zone is minimal, or does not warrant a water booster
station, the Town Engineer may permit alternative measures
to be employed. Alternative measures shall be consistent
with the National Plumbing Code, and must increase the
available pressure as close as possible to the 200 kPa
requirement. Alternative measures may include, but are
not limited to, the following:
58
-
provision of increased diameter service laterals and
increased diameter residential plumbing to provide a
system hydraulically equivalent to a 200 kPa static
pressure system serviced through standard diameter
service laterals, and minimum diameter residential
plumbing;
-
provision of individual residential booster pumps within
each serviced dwelling or structure to increase the
available pressure as close as possible to the 200 kPa
requirement.
5.2.3 Maximum Pressures
Water distribution systems must be designed and sized in order to operate
under a normal range of pressures from 200 kPa to 600 kPa
under Maximum Daily Demand conditions.
The maximum pressure in the water distribution system should not exceed
700 kPa in order to avoid damage to residential plumbing
systems, fixtures, and appurtenances.
5.2.4 Maximum Velocities
Water distribution systems must be designed and sized such that the maximum
velocity in the pipe must not exceed the following:
-
1.5 m/s during Maximum Hourly Demand;
-
2.4 m/s during Fire Flow.
5.2.5
Hazen-Williams Roughness Coefficient (CHW)
Water distribution systems must be designed and sized assuming an ultimate
pipe friction will be attained over long term operation. Table 5.2 presents Hazen-
Williams roughness coefficients (CHW) that shall be applied regardless of the pipe
material.
Table 5.2
Hazen-Williams Roughness Coefficients (CHW)
Pipe Diameter
CHW
NPS-6
100
NPS-8 to NPS-10
110
NPS-12 to NPS-24
120
NPS-24 and greater
130
5.2.6
Materials
59
All water distribution system materials not specified herein are to be as per the
Standard Specification for Municipal Services for Nova Scotia.
5.2.7
Minimum Diameter
Water distribution systems must be designed and sized to meet all of the criteria
outlined above, but under no circumstances shall be less than 150 mm in
diameter.
5.2.8
Minimum Cover
All watermains must be designed with a minimum cover of 1.7 m as measured
from the finished grade to the top of the pipe.
.2.9
Maximum Cover
The cover as measured from the finished grade to the top of the pipe may
be increased to a suitable depth to prevent freezing of
either the watermain or the services, but under no
circumstances shall the cover exceed 2.4m unless approved
by the Town Engineer.
5.2.10 Location
In the case of common trench installations, the watermain must be laid
adjacent to the sanitary sewer with a minimum 0.9 m
horizontal separation, and a minimum 0.30m vertical
separation, with the watermain being located above the
sanitary sewer.
All watermain and appurtenances must be located within the street right-
of-way owned by the Town of Amherst or the Nova Scotia
Department of Transportation and Public Works. In the
case of off-street servicing, all watermain and
appurtenances must be located within a 6.0 m wide
municipal service easement granted to the Town of Amherst.
Contingent upon the length and location of the municipal
service easement, the Town Engineer may require a suitable
travelled way to be provided within the easement for
operations and maintenance purposes.
In the case of curb and gutter street design, all watermain and
appurtenances must be located within the travelled way and
no closer than 1.8 m of the curb line.
In the case of open ditch street design, all watermain and appurtenances
may be located in the gravel shoulder.
In the case of municipal service easement installations, all watermain
and appurtenances must be located as close as possible to
60
the centreline of the easement.
Where a need is identified to accommodate future development on adjacent
lands, municipal service easements must be provided from
the edge of a street right-of-way to the property boundary
of the subdivision subject to approval of the Town
Engineer.
5.2.11 Grid Design and Looping
The layout of water distribution systems must be based on a grid design of
closed loops wherever possible. Municipal service easements must be provided
in order to provide closed loops where the street right-of-way does not. The
occurrence of dead-end watermains should be minimized, or eliminated. Where
dead-end watermains cannot be avoided, they shall be provided with a fire
hydrant, or acceptable blow-off to provide the opportunity for disinfection and
flushing. Additional looping may be required to increase the reliability of the
system at the discretion of the Town Engineer.
5.2.12 Water Mains
Ductile iron pipe shall be supplied in minimum pressure class 350 for 100 mm
through 350 mm, pressure class 250 for 350 mm through 500 mm cement morto
lined. Materials, fittings and appurtances shall be in accordance with American
Water Works Association (A.W.W.A) specifications.
PVC pipe shall be to CSA B137.3 M90, series 160 unless otherwise agreed to by
the Town, or to AWWA C900-89 for pipe sizes 100 mm to 300 mm, DR 18
(pressure class 1034 kPa) unless otherwise agreed to by the Town or AWWA
C905-88 for pipe sizes 350 mm to 900 mm, DR 18 (pressure class 1620 kPa)
unless otherwise agreed to by the Town. All pipe shall be certified to CSA B
173.3 M90, shall be U.L. and F.M. approved, and shall have 1 Mpa gasket bell
end, cast iron outside diameter.
Water mains shall be installed in accordance with AWWA Specifications C600-
54T and the Nova Scotia Municipal Service Specification.
5.2.13 Isolation Valves
All connections to an existing water distribution system must provide an isolation
valve so that the connection can be isolated from the existing water distribution
system. The Town can not guarantee leak-proof operation of existing valves,
therefore, it is recommended that a new valve be installed when connecting to
existing mains.
The connection to an existing water distribution system must be coordinated by
the Consultant with the Town Engineer. Any such connection is to be witnessed
by the Consultant and the Town Engineer. All tapping of existing water
distribution systems for such connections must be conducted and inspected with
the existing water distribution system operating under working pressure.
61
All valves must be gate valves and shall be provided on water distribution
systems to satisfy the following conditions:
-
Isolation valves must be provided on each leg of intersections to permit
isolation of any section by operating not more than three valves;
-
A sufficient number of isolation valves must be provided to allow for shut-
down of any section without putting more than 40 customers out of service at
any time;
-
A sufficient number of isolation valves must be provided so that a break or
other failure will not affect more than 150 m of water distribution system in
commercial districts, or 250 m of water distribution system in residential
districts.;
-
Where water distribution systems serve customers located on large rural lots,
and where future development is not expected, isolation valve spacing must
not exceed 425 m.
-
Gate valves shall be McAvity, Bibby, Mueller, AVK or approved equal and
each shall be accommodated in a valve box.
5.2.14 Automatic Combination Air Relief and Vacuum Valves
Automatic combination air relief and vacuum valves must be installed in an
appropriate insulated manhole structure at all significant high points in the
distribution system, and at other locations as required by sound engineering
judgement, or at the discretion of the Town Engineer.
5.2.15 Drain Valves
Water distribution systems exceeding 300 mm in diameter must be equipped with
drain valves located at low points to permit drainage during maintenance and
repairs to the system.
Water distribution systems less than 300 mm in diameter must be equipped
with hydrants located at low points to permit draining
through pumping or compressed air during maintenance and
repair to the system.
.2.16
Fire Hydrants
Fire hydrants must be provided at a recommended spacing in accordance with
the latest requirements contained in the publication Water Supply for Public Fire
Protection - A Guide to Recommended Practice, as prepared by the Fire
Underwriter's Survey (FUS) in conjunction with the Insurers' Advisory
Organisation (IAO). Under no circumstances shall the maximum fire hydrant
spacing exceed 300 m.
The following are desirable fire hydrant locations:
62
-
Fire hydrants should be located at localized high points in the water
distribution system, unless an automatic combination air release and vacuum
valve is required at that location;
-
Fire hydrants should be located at localized low points in the water
distribution system, unless a drain valve is required at that location;
-
Fire hydrants should be located at intersections of roads;
-
Fire hydrants should be located at the end of dead-end streets or cul-de-sacs.
5.2.17 Fire Hydrants Materials
-
Gate valves must be provided for all hydrants.
-
Laterals between the water main and fire hydrant must be a minimum of 150
mm in diameter.
-
Hydrants shall be of the break-away type.
-
Hydrants shall be McAvity M67-Brigadier, internally plugged, and be equipped
with 2-65 mm diameter hose connections. A 114 mm Storz connection must
be provided. All threads to be to the Town of Amherst Standard. Color to be
yellow.
5.2.18 Fittings
Any horizontal or vertical change in direction exceeding the manufacturer's
recommended maximum deflection tolerance at a pipe joint requires an approved
bend.
5.2.19 Joint Restraint
Calculation of thrust forces on pipe joints and fittings should account
for normal operating pressure plus pressure transients
induced at peak flow velocity plus dynamic thrust if the
peak flow velocity is excessive.
Joint restraint must be provided for the following fittings and
appurtenances:
-
caps and plugs;
-
tees and wyes;
-
reducers and enlargers;
-
horizontal and vertical bends;
-
valves;
-
hydrants.
Thrust blocks must be provided at fittings and appurtenances requiring
joint restraint and shall consider the soil bearing
capacity of the in-situ material that the thrust block
bears against. The Consultant should exercise sound
engineering judgement in order to account for reduced
63
bearing capacity associated with shallow trench
installations.
Mechanical joint restraint systems may be used in lieu of thrust blocks at the
discretion of the Town Engineer. The Consultant should exercise sound
engineering judgement in the design of mechanical joint restraint systems
recognizing that not only the fittings and appurtenances require restraint, but
adjacent pipe sections require restraint in order to develop adequate skin friction
equal to the restraint offered by the thrust block. The number of restrained joints
and number of restrained pipe runs should be clearly identified on plan and
profile drawings.
5.2.20 Trench Drainage Relief System
The Consultant shall assess the possibility of groundwater migration, caused by
an elevated water table, through pervious bedding and backfill material, and shall
be responsible for the design of corrective measures to prevent flooding as a
result of this groundwater migration.
Water distribution systems installed in a separate trench, or installed in areas
where sanitary sewer mains and/or storm sewer mains are not installed must
require a trench drainage relief system to lower the elevated water table in the
trench below the invert of the watermain.
5.2.21 Service Laterals
All water service laterals must be designed with a minimum cover of 1.6 m as
measured from the finished grade to the top of the lateral including the goose
neck.
All water service laterals from the watermain to the property line must be
provided by the Developer. A single water service lateral is to be supplied to each
existing lot or potential future lot that could potentially be created under the land
use bylaw in effect at the time of installation of the water distribution system.
Whenever possible, water service laterals should not be installed in private
driveways or other travelled ways.
In order to avoid high friction losses in water service laterals, the maximum length
of any 19 mm diameter water service lateral must be limited to 55 m from the
curb stop to the dwelling or structure. Water services laterals longer than 55 m
must be a minimum of 25 mm in diameter.
5.2.22 Water Service Laterals Materials
Each single unit detached residential property will be provided with a water
service of 19 mm (minimum) type "K" soft copper to the curb stop meeting
A.S.T.M Standard B88. Service connections for other occupancies will depend
on fire regulations and the National Plumbing Code and are to be approved by
the Town Engineer.
Service laterals shall consist of the connection to the main and a curb stop with
stainless steel rods, located on the property line.
64
5.2.23 Backflow Prevention Devices
Backflow prevention devices are required on new services if there is a risk of
contamination of the potable water supply. Premises which require backflow
prevention devices include, but are not limited to, the following:
-
industrial, commercial, and institutional buildings;
-
apartment buildings larger than four units;
-
sprinkler service lines.
5.2.24 Testing
Prior to final testing and disinfection the mains shall be flushed. Appropriately
sized water main swabs shall be inserted into the newly constructed water main
to ensure that each newly installed section of water main is swept by a swab
when the system is flushed. After the main has been swabbed, hydrant leads will
be thoroughly flushed by opening and closing hydrants and valves several times
with an adequate flow velocity to remove foreign material and debris.
Only Town staff are authorized to operate valves and hydrants during filling
and flushing.
The consultant must test for chlorine residual at chlorination and after 24 hours
and forward results to Town Engineer.
Disinfection to be carried out in accordance with Nova Scotia Standard
Specification for Municipal Services.
De-chlorination must be performed prior to disposal of water on site in
situations where chlorinated water cannot be discharged to the sanitary
sewer. Under no circumstances shall chlorinated water be allowed to be
discharged to the surface or a watercourse.
5.3
Domestic Water Pumping Station
5.3.1
General Requirements
As a result of differences in ground elevations, or distance from the
source of supply, isolated areas may require increasing
the pressure of the water system to adequately meet
minimum pressure and fire flow requirements as outlined
elsewhere in this standard.
In order to accomplish this, a water booster station may be required to
adequately service a specific area within the Water
Service District. Such areas, or Pressure Zones, are
generally isolated from the remainder of the water
distribution system.
Water booster stations may incorporate either ground storage reservoirs
or elevated storage reservoirs into their design and
65
operation. The incorporation of such storage is normally
done in order to supply extreme demand requirements such
as Maximum Hourly Demand or Fire Flow.
5.3.2
Floating Storage
Water booster stations, without floating storage, must be designed and
sized in order to supply the extreme water demand
conditions outlined in Section 5.2.2.
In the case of small pressure zones that do not have ground storage or
elevated storage available, the necessity to meet Fire
Flow Demand is the most critical.
In the case of large pressure zones that do not have ground storage or
elevated storage available, the necessity to meet the
extreme water demands directly from the water booster
station may become cost prohibitive. Floating storage
facilities become economically viable for large pressure
zones and shall be incorporated into the system at the
discretion of the Town Engineer.
Water booster stations, with floating storage, must be designed and sized
in order to supply the Maximum Hourly Demand as outlined
in Section 5.2.2. Floating storage must be available for
water balancing and Fire Flow Demand conditions.
.3.3
Pump System Capacity
Water booster stations, without floating storage, must be designed and
sized with a minimum of one lead and two lag domestic
pumps. Domestic pumps must be designed and sized such
that the capacity of the pumping station with the two
largest pumps out of service must provide a minimum of 80%
of the peak demand of the serviced area when completely
developed.
Water booster stations, with floating storage, must be designed and sized
with a minimum of one lead and two lag domestic pumps.
The domestic pumps must be designed and sized such that
the capacity of the pumping station with the largest pump
out of service must provide a minimum of 80% of the peak
demand of the serviced area when completely developed.
The lead pump must provide a maximum of 25% of the peak demand and
provide an adequate supply during normal periods of
domestic demand.
The lag pumps must provide a maximum of 55% of the peak demand and
66
provide an adequate supply during maximum periods of
domestic demand.
The fire pump must have adequate capacity to supply the necessary fire
flow demand.
The use of variable speed pumps is preferred to compensate for the demand
variations.
5.3.4
Domestic Pumps and Fire Pumps
Domestic pumps, fire pumps, and all fittings and appurtenances including
system capacity, system sizing, system layout, control
facilities, installation, and testing, must meet all
applicable and relevant standards and codes.
5.3.5
System Head Curves
A single system head curve can not be developed due to fluctuations in
water demands within the system. Therefore, projected
points of operating head and flow for at least the
following conditions shall be developed:
-
Average Daily Demand;
-
Maximum Daily Demand;
-
Maximum Hourly Demand (A.M.);
-
Maximum Hourly Demand (P.M.);
-
Minimum Hourly Demand (Night).
Pumps that adequately operate over the anticipated range of demands at
the station from a minimum total dynamic head to a maximum
total dynamic head shall be selected. Generally, the
pumps must be capable of meeting the following criteria:
-
the rated point corresponding to the Maximum Daily Demand
condition;
-
the rated point corresponding to the maximum efficiency;
-
the rated point corresponding to the minimum total dynamic head and the
maximum total dynamic head;
-
the minimum submergence level for a vertical turbine unit;
-
the available NPSH for a horizontal centrifugal unit;
67
In general, pumps operate at a total dynamic head considerably less than
the manufacturer's ultimate rated point. Therefore, the
maximum efficiency point shall be specified as that point
at which the pump will normally run. The rated point
shall be selected as the point at which the pump will
overcome the greatest amount of head for a specified flow
rate.
Pumps shall be selected in order to avoid the following
conditions:
-
pumps subjected to low total dynamic head may be prone to destructive
cavitation under high flow conditions;
-
pumps subjected to high total dynamic head may be prone to high power
consumption under low flow conditions;
-
noise and vibration levels that are audible beyond the immediate station
vicinity.
5.3.6
Site Considerations
5.3.6.1 Site Access
Vehicle access to the water booster station must be provided in order to
accommodate the need for maintenance and service personnel
and vehicles.
The driveway shall be constructed of 300 mm thick crushed stone.
Town approved access hatchways and doorways must be provided. All locks
must be keyed alike to the Town of Amherst standard with
keys provided to the Town.
.3.6.2
Site Ownership
All structures, fittings, and appurtenances associated with the water
booster station must be located on property outside of the
street right-of-way in an appropriate area. The ownership
of this property must be deeded to the Town of Amherst.
5.3.6.3 Flooding
Water booster stations and appurtenances should be protected from
flooding and flood related damage due to the 1 in 100 year
storm.
Water booster stations and appurtenances should remain operational in the
1 in 100 year storm.
Water booster station land must be graded such that ponding of water does
not occur. All exposed areas must be sodded/hydroseeded.
68
5.3.6.4 Site Location
All structures and appurtenances associated with the booster station must
be located off the street right-of-way in an appropriate
area specifically designated for that purpose. The
ownership of this property must be deeded to the Town of
Amherst.
5.3.6.5 Equipment Removal
All water booster stations must be equipped with acceptable devices for
the removal and maintenance of pumps, motors, controls,
and auxiliary power equipment.
5.3.7
Civil
The pump house building must be of adequate size to accommodate the
pumps, pump motors, control panel, auxiliary power supply,
oil tank, and other accessories. These items must be
located in the building taking into consideration safety
for operators and convenient access for maintenance.
The pump house building design and construction must meet the
requirements of the latest edition of the National
Building Code. Exterior wall assembly shall be 200 mm
split face concrete block with a minimum of R-10
insulation. There shall be no windows in any exterior
wall.
Ventilation for all mechanical equipment must be vandal-resistant, heavy
duty type steel intake and exhaust louvres. Engine
emissions must be directed away from the building so as
not to create a ventilation "short circuit". Provisions
must be made to support wall-mounted equipment inside the
building. The building shall have a hip roof with a
minimum slope of 12 horizontal to 6 vertical and have a
minimum of R-20 insulation.
The building floor must be a minimum 150 mm above the external ground
surface and any potential flood level. Pump-house floors
must be poured reinforced concrete and sloped towards the
access door. All interior wall surfaces, doors, and trims
should be painted to a colour scheme as approved by the
Town Engineer. A non-metallic coloured hardener shall be
added to the concrete floors during the finishing process
to a colour scheme as approved by the Town Engineer.
Lifting devices of a type approved by the Town Engineer should be
incorporated into the design of the structure so that
pumps and/or motors can easily be transferred from their
location within the station to an access door.
69
All locks must be keyed alike to the Town of Amherst standard system.
5.3.8
Electrical & Miscellaneous
The pumping station must be provided with a three phase power supply.
Design and installation of the power supply system must
meet all applicable and relevant standards and codes.
Full standby power supply must be provided utilizing a standby diesel
generator set. The power generating system must be
capable of providing continuous electric power during any
interruption of the normal power supply. The standby
power unit must be designed with adequate capacity to
operate fire and domestic pumps, control and monitoring
systems, and heating and lighting systems within the pump
house.
The generating system must include the following items:
-
diesel engine;
-
alternator;
-
control panel;
-
automatic change-over equipment;
-
automatic ventilation system;
-
battery charger and battery;
-
fuel supply unit.
Pumping station equipment must be equipped with control systems,
compatible with the pumping station monitoring system.
The control system must be capable of providing:
-
uninterrupted fully automatic operation of the pumping station to meet the
various demand requirements of the area being serviced;
-
protection against equipment damage or failure during extreme hydraulic or
electrical conditions.
Each pump shall be operated by an energy efficient electric motor capable
of operating the pump over the full range of load
conditions. Motors should be located such that they
cannot be flooded should a pipe failure occur.
All electrical apparatus shall be located in an accessible location above
grade with a clear access of 1.0 m around all pumps and
motors. All panels and controls must be moisture-
resistant.
70
Pump house must contain at least the following:
-
electric unit heaters with individual built-in thermostats;
-
adequate vapour proof lighting;
-
a single photo-cell activated outside vandal proof security light adjacent to or
over the access door;
-
a weather-proof switch and electrical outlet inside the pump-house
immediately adjacent to the access door;
-
adequate lightning arrestors;
-
a fire extinguisher;
-
sufficient ventilation to ensure that heat generated from the electrical
equipment is sufficiently dissipated.
5.3.9
Mechanical
Suction and discharge piping must be designed and arranged to provide
easy access for maintenance. All piping and tubing, 100
mm diameter and smaller, must be stainless steel, Type 316
or 316L, Schedule 40, unless otherwise approved by the
Town Engineer. All ductile iron piping within the station
must be Class 54, cement lined. Threaded flanges must be
used for all joints, fittings and connections within the
station.
All piping within the pumping station must be properly supported and must
be designed with appropriate fittings to allow for
expansion and contraction, thrust restraint, etc. All
exposed surfaces and pipes, other than stainless steel,
must be finished, treated, and painted to prevent rusting.
Colour scheme and paint types shall be approved by the
Town Engineer.
A self-closing check valve must be incorporated in the discharge of each
unit in the pumping station. It must be designed in such
a way that if pump flow is lost, the valve will close
automatically. The type and arrangement of check valves
and discharge valves is dependent on the potential
hydraulic transients that might be experienced in the
pumping station.
An adequate number of isolation valves must be provided to allow
maintenance of pumps and/or control valves.
In an in-line booster pumping station, the pressure on the suction side
71
of the pump must not be allowed to drop below 150 kPa when
there are service connections on the suction side
watermain.
5.3.10 Pressure Transients
Water distribution systems must be designed and sized in order to
withstand maximum operating pressures plus pressure
transients. Pressure transients, or surges, result from
sudden changes in flow velocity within the water
distribution system. These sudden changes in velocity are
most often the result of rapid valve operation, pump
start-up and shut-down, sudden demand fluctuations, and
power failures.
Pipe and pipe joints must be able to minimally withstand the pressure transient
created by the instantaneous stoppage of a water column travelling at 0.6 m/s.
The magnitude of the pressure transient will vary as a function of pipe diameter,
pipe wall thickness, and pipe wall material.
Celerity values expressed in many texts and manufacturer's catalogues for
flexible pipe are for the unrestrained condition.
Flexible pipe, when buried, often exhibits an effective
celerity much higher than published values. The
Consultant should exercise sound engineering judgement to
account for this increased effective celerity. A rule of
thumb approach is to assume an effective celerity twice
that of the published value for flexible pipe.
Typical methods of surge protection that can be used to protect the
booster station and equipment include the following:
-
surge anticipator systems that dissipate over-pressure from the discharge
lines;
-
slow closing and opening control valves on pump discharges;
-
hydro-pneumatic surge tanks on discharge headers;
-
variable speed pumping units.
5.3.11
Safety Precautions
The pumping station and appurtenances must be designed in such a manner as
to ensure the safety of operators, in accordance with all applicable Municipal,
Provincial, and Federal regulations including the Occupational Health & Safety
Act of the Province of Nova Scotia.
-
All moving equipment must be covered with suitable guards and shields to
prevent accidental contact by operations and maintenance personnel;
-
All self-starting equipment must be labelled with suitable warning signage to
ensure that operations and maintenance personnel are aware of this
situation;
72
-
All equipment must be equipped with lock-outs to ensure that the equipment
is completely out of service when operations and maintenance personnel are
working on the system.
5.3.12 Pumping Station Monitoring
Pumping station functions must be monitored using an integrated Supervisory
Control and Data Acquisition (SCADA) system to ensure that the station is
performing satisfactorily. All software is to be fully compatible with the Town of
Amherst central SCADA system. The SCADA unit must have two extra digital
points and two extra analog points and must be capable of transmitting the
following signals and alarms to the central monitoring location:
-
station flow;
-
station suction pressure;
-
station discharge pressure;
-
station voltage;
-
amperage.
-
pump status (On/Off);
-
low discharge pressure alarm;
-
high discharge pressure alarm;
-
motor current overload alarm;
-
motor temperature overload;
-
surge valve alarm.
-
pump status (On/Off);
-
low discharge pressure alarm;
-
high discharge pressure alarm;
-
motor current overload alarm;
-
motor temperature overload alarm.
Standby Power Unit Alarms
-
power failure alarm;
-
generator status (On/Off);
-
hand-off automatic selector switch status (On/Off);
-
battery status (charged/charging);
-
fuel tank level (diesel only);
-
fuel tank pressure (propane only);
-
generator current overload alarm;
-
generator temperature overload alarm.
Building Alarms
-
panic alarm;
-
building fire alarm;
73
-
illegal entry alarm;
-
building temperature alarm - lo & hi;
-
building flood alarm.
5.3.13 Operation and Maintenance Manual
Three copies of the pumping station operation and maintenance manual must be
prepared in a form acceptable to the Town Engineer, and provided to the Town
Engineer prior to acceptance of the pumping station. This manual must contain
at least the following:
-
system description;
-
design parameters, system hydraulics and design calculation;
-
as constructed civil, mechanical, and electrical drawings;
-
pump literature, pump curves, and operating instructions;
-
manufacturers' operation and maintenance instructions for all equipment;
-
name, address, and telephone number of all equipment suppliers and
installers;
-
information on guarantees/warranties for all equipment.
All special tools and standard spare parts for all pumping station equipment is to
be provided by the contractor prior to acceptance of the system by the Town of
Amherst.
74
STORM DRAINAGE SYSTEM
6.1
Scope
A storm drainage system is a system receiving, conveying, and controlling discharges in
response to precipitation and snow melt. Such systems consist of ditches, culverts,
swales, subsurface interceptor drains, roadways, curb and gutters, catchbasins,
manholes, pipes, retention ponds, and service lateral lines. The design criteria contained
in this section is included to illustrate the more common aspects encountered in the
design of storm drainage systems.
All storm drainage systems within the Town of Amherst shall be designed to achieve the
following objectives:
-
to prevent loss of life and to protect structures and property from damage due to storm
events;
-
to provide safe and convenient use of streets, property, and other improvements
during and following precipitation and snow melt events;
-
to adequately convey stormwater runoff from upstream sources;
-
to mitigate the adverse effects of stormwater runoff, such as flooding and erosion,
onto downstream properties;
-
to preserve natural watercourses and wetland environment;
-
to minimize the long-term effects of development on the receiving surface water and
groundwater regimes from both a quantity and quality perspective.
In the Town of Amherst, storm drainage systems are owned, operated, and maintained by
either the Town of Amherst, private landowners, or a combination of both.
The management and control of stormwater is a mixture of art and science, and like all
other municipal services, storm drainage systems must be carefully designed, reviewed,
and approved before construction proceeds.
All storm drainage systems shall conform to the latest revision of the Storm Drainage
Works Approval Policy by the Nova Scotia Department of Environment and Labour
(NSDEL) on December 10, 2002.
Proposed storm drainage works must be based on sound engineering design. For
stormwater design work, this often requires good quality hydrologic and hydraulic
modeling. Stormwater modeling can be divided into two basic fields:
Hydrology, which is the study of runoff produced from rainfall and/or snowmelt, and the
factors which influence it, and
Hydraulics, which is the study of water flow in the channels, pipes, streams, ponds, and
rivers which convey it to the sea. In each field, there are many techniques available for
performing the required analysis, which requires a qualified professional engineer to
choose the best methods for each situation.
75
6.2
Design Approach
6.2.1
Storm Drainage System Types
New developments shall be serviced by a dual drainage system consisting of
both a minor storm drainage system (piped system) and a major storm drainage
system (overland system).
6.2.2
Dual Storm Drainage System Design
Design of storm drainage systems shall include consideration of both a minor
storm drainage system and major storm drainage systems. The design of the
dual storm drainage system, including the minor system and the major system,
shall be carried out to ensure that no proposed or existing structure shall be
damaged by the runoff generated by any storm up to the 1 in 100 year return
period storm. This requires proper care in the design of streets, curb and gutters,
catchbasins, pipes, open channels, grading of lots and road profiles, setting of
elevations or openings into buildings, foundation drains, roof drains, or other "off-
street" connections.
6.2.2.1 Minor Storm Drainage System
The minor storm drainage system shall be designed to convey stormwater runoff
from the 1 in 5 year return period storm, thereby providing safe and convenient
use of streets and other areas. The minor storm drainage system shall consist of
the following components:
-
swales, subsurface interceptor drains, curb and gutters, catchbasins,
manholes, pipes or conduits and service lateral lines in those areas where a
piped storm drainage system is required.
6.2.2.2 Major Storm Drainage System
The major storm drainage system shall be designed to convey stormwater runoff
from the 1 in 100 year return period storm, thereby preventing loss of life and
protecting structures and property from damage. The capacity of the major storm
drainage system shall be adequate to carry the discharge from a major storm
event when the capacity of the minor storm drainage system is exceeded. The
major storm drainage system shall consist of the following components:
-
ditches, open drainage channels, swales, roadways, detention ponds,
watercourses, floodplains, gullies, and creeks in those areas where a piped
storm drainage system is required for the minor drainage system;
-
ditches, open drainage channels, swales, roadways, watercourses,
floodplains, gullies, and creeks in those areas where an open channel
drainage system is required for the minor drainage system.
76
6.2.3
Storm Drainage System Outfall
The dual storm drainage system consisting of the minor storm drainage system
and the major drainage system shall be extended to discharge to an existing
downstream storm drainage system, or natural watercourse.
6.2.4
Existing Storm Drainage System Outfall
The downstream storm drainage system shall have adequate capacity to capture
and convey discharge from the proposed storm drainage system in addition to its
own base flow rate of discharge. Any potential adverse impact, such as flooding
or erosion, as a result of the combined rate of discharge, on the downstream
storm drainage system shall be investigated. Such investigation shall be carried
out from the outfall location of the proposed storm drainage system to a location
in the downstream watercourse where the peak rate of discharge from the
proposed storm drainage system is 10% of the combined peak rate of discharge
in the watercourse at that location.
The extent of any adverse impacts will be assessed by the Town Engineer based
on this investigation. Depending upon the nature of any adverse impacts, the
Town Engineer may require mitigative measures to be provided to the storm
drainage system to prevent or alleviate such adverse impacts.
6.2.5
Design Parameters
6.2.5.1
Basis of Design
Design of the dual storm drainage system shall be based on the state of
development anticipated to exist for both the subwatershed under design and
upstream subwatershed when both areas are completely developed in
accordance with the land-use zoning in place at the time of design.
6.2.5.2
Design Flow
6.2.5.2.1 Developed Areas
Except as indicated below, design flows for residential, commercial, or industrial
land uses shall be based on summer rainfall data and corresponding runoff
coefficients for summer conditions.
6.2.5.2.2 Undeveloped Areas
When the area under design includes greater than 50% designated for future
development, peak design flows shall be the largest of flows estimated for both
winter and summer conditions.
6.2.5.2.3 Long Duration
77
When the area under design requires calculation of flows for durations greater
than 6 hours, design flows shall be the largest of the flows estimated for both
winter and summer conditions.
6.3
Meteorological Data
Rainfall data is used in a variety of forms including intensity-duration-frequency
curves, synthetic design storms, historical design storms, and historical long-term
rainfall records. Selection of the proper form depends upon the type of
computational procedure to be used, contingent upon the type of problem to be
solved and the level of analysis required.
6.3.1
Rainfall Intensity - Duration - Frequency Curve
Figure 6.1 contains rainfall intensity - duration - frequency curves which are
based on annual rainfall at the Moncton International Airport (MIA) weather
station. Additional detailed historical rainfall information is available through the
Atmospheric Environment Service (AES) of Environment Canada.
78
6.3.2
Synthetic Design Storm
Advanced procedures for the design of storm drainage systems requires the
input of rainfall hyetographs, which specify rainfall intensities for successive time
increments during a storm event. For this purpose, it is standard to use both
synthetic and historical design storms hyetographs. Synthetic design storm
hyetographs are intended to represent some of the long term statistical
properties of recorded rainfall.
6.3.3
Historical Design Storm
In some instances the design of storm drainage systems requires the input of
historical design storms. Historical design storm hyetographs are intended to
represent a specific recorded rainfall. Additional detailed historical rainfall
information is available through the Atmospheric Environment Service (AES) of
Environment Canada.
FIGURE 6.1
ANNUAL RAINFALL INTENSITY-DURATION FREQUENCY CURVES FOR MONCTON (1946 - 1997)
Environment Canada - Atmospheric Environment Service
1
10
100
1000
1
10
100
1000
10000
DURATION (minutes/hours)
INTENSITY (mm/hr)
60
5
20
30
12
8
2
24
10
100 yr
50 yr
25 yr
10 yr
5 yr
2 yr
R = A * T ^ B
A B
2yr 17.3 -0.607
5yr 24.3 -0.626
10yr 29.0 -0.634
25yr 34.9 -0.641
50yr 39.2 -0.644
100yr 43.6 -0.647
Where:
R- mm/hr
A - coefficient
T - hr
B-coefficient
79
6.4
Runoff Methodology
There are numerous techniques and models available to the Consultant for use
in the determination of stormwater runoff. Selection of an appropriate method
must be based on an understanding of the principles and assumptions underlying
the method and of the problem under consideration. It is, therefore, essential
that appropriate techniques and models be selected and used by experienced
engineers.
The following list of computational methods is not to be considered complete and
comprehensive. Its intention is to provide general comments on several of the
methods accepted by the Town of Amherst Operational Services.
6.4.1
The Rational Method
The Rational method is the most widely used empirical equation for predicting
instantaneous peak discharge from a small subwatershed. The peak discharge
is assumed to occur at a rainfall duration equal to the time of concentration. The
Rational method may be used for the determination of instantaneous peak runoff,
in the design of storm drainage systems up to 20 hectares in area, for preliminary
design of systems serving larger areas, and as a check on flows determined by
other methods. This method cannot be used to determine the size or hydraulic
performance of storage facilities.
6.4.2
HEC
The United States Army Corps of Engineers (USACE) HEC model may be used
for modeling overland storm drainage systems, natural watercourses and
determining the extent of floodplains.
Methods other than those listed above may be used if their use is justified by the
Consultant and approved by the Town Engineer. Results may need to be verified
by checking with a second method, or calibration based on flow measurement.
6.5
Hydrologic Design Criteria
6.5.1
Rational Method
6.5.1.1 Runoff Coefficients
Table 6.1 and Table 6.2 present Rational method runoff coefficients appropriate
for various land uses and surface types. Selection of values from Table 6.1 and
Table 6.2 shall be based on a percent of impervious area, lot size, soil
conditions, and other relevant considerations. For residential, commercial or
industrial land uses, rainfall intensities from Figure 6.1 shall be used with
coefficients for summer ground conditions. Where runoff from an area that
includes a significant proportion of undeveloped land is to be determined, a
comparison shall be made between summer and winter ground conditions using
winter runoff coefficients from Table 6.3 and rainfall intensities from Figure 6.1
accounting for snowmelt contributions. For winter or year-round runoff
calculations, the coefficients from Tables 6.1, 6.2, and 6.3 shall be increased
80
according to Table 6.4 for the 1 in 100 year return period.
81
Table 6.1
Rational Method Runoff Coefficients for Various Areas for the Summer
Condition
Character of Area
Description of Area
Runoff Coefficient
Light
0.50 to 0.80
Industrial
Heavy
0.60 to 0.90
Downtown
0.70 to 0.95
Commercial
Neighbourhood
0.50 to 0.70
Single-Family
0.30 to 0.50
Attached Multi-Unit
0.60 to 0.75
Suburban
0.25 to 0.40
Apartment
0.50 to 0.70
Residential
Park, Cemetery
0.10 to 0.25
Playground
0.20 to 0.40
Railroad Yard
0.20 to 0.40
Unimproved/Vacant
Lands
0.10 to 0.30
Other
Table 6.2
Rational Method Runoff Coefficients for Various
Surfaces for the Summer Condition
Description of Surface
Runoff Coefficient
Asphalt
0.70 to 0.95
Concrete
0.80 to 0.95
Brick
0.70 to 0.85
Impervious
Rooftop
0.75 to 0.95
Lawn, Sandy Soil, < 2%
0.05 to 0.10
Lawn, Sandy Soil, 2%-7%
0.10 to 0.15
Lawn, Sandy Soil, > 7%
0.15 to 0.20
Lawn, Clayey Soil, <2%
0.13 to 0.17
Lawn, Clayey Soil, 2%-
7%
0.18 to 0.22
Pervious
Lawn, Clayey Soil, >7%
0.25 to 0.35
Note: Higher values than those presented in Table 6.2 are required to account for steeply
sloped areas, longer duration events, and longer return periods to account for decreased
infiltration and other losses.
Table 6.3
Rational Method Runoff Coefficients for the Winter Condition
Character of
Area/Surface
Return Period
Runoff Coefficient
82
All areas/surfaces
with
Summer coefficient <
0.80
5 year
0.80
All areas/surfaces
with
Summer coefficient <
0.80
100 year
1.00
Table 6.4
Rational Method Runoff Coefficients for the 100 Year Return Period
Runoff Coefficient for
5 to 10 Year Return Period
Corresponding Runoff Coefficient for
100 Year Return Period
0.10
0.20
0.20
0.35
0.30
0.50
0.40
0.65
0.50
0.80
0.60
0.90
0.70 to 1.00
1.00
6.5.1.2 Winter Runoff
Where calculation of winter runoff is required, frozen ground shall be simulated
by assuming the area to be 80% paved in a 1 in 5 year design storm and 100%
paved in a 1 in 100 year design storm, and the time of concentration (Tc) shall be
adjusted to reflect flow over frozen ground.
6.5.1.3 Snowmelt
Estimation of snowmelt contribution is a complex process dependent on a
number of variables, often not published for a given region. In lieu of available
data, estimated snowmelt of 1.5 mm per hour shall be added to winter rainfall
intensity as determined above.
6.5.1.4 Time of Concentration
For most piped systems in medium density urban areas, it is expected that a
minimum five minute inlet time (Ti) will be used. Travel times (Tt) in piped
systems should be based on velocities at peak design flow.
6.6
Storm Drainage Report
A storm drainage report shall be prepared and included as part of the submission
for any subdivision to examine the effect of the development on the receiving
watercourses and downstream drainage systems.
The storm drainage report shall include a Storm Servicing Schematic consistent
83
with the submission requirements outlined as follows:
6.6.1 Schematic Servicing Plans
Stormwater Schematic Servicing Plans must include the following in either graphic
and/or tabular form:
- the location of the subdivision within the total topographic drainage area;
- site layout including proposed streets, lots and approximate location of
proposed structures;
- pre-development contours at an interval not exceeding 2.5m;
- hydraulic grade line, or pressure zone;
- any additional information deemed necessary by the Town Engineer.
Wherever possible, Schematic Servicing Plans are to be drafted in one of
the following standard metric ratios:
-
1 : 500
-
1 : 1,000
-
1 : 2,000
6.7
Design Requirements
6.7.1
Minor Storm Drainage System
6.7.1.1 Hydraulic Design
Minor storm drainage systems shall be designed to convey, without surcharge,
the 1 in 5 year return period storm.
The capacity of a proposed storm sewer system or an existing storm sewer
system shall be checked by accounting for the headloss through the pipe system
and through any junctions including manholes and bends. As a preliminary
check on the capacity of a piped storm system, the Manning's equation can be
used. This will be particularly useful for sizing the pipes in the first instance;
however, a more detailed analysis of the system as a whole will be required.
This analysis will determine the hydraulic gradeline (HGL) when the storm system
is conveying the 1 in 5 year flows, and will take into account losses at manholes
and other junctions, the headloss through the pipes, and any backwater
conditions at the outlet of the storm sewer system.
84
To ensure that the minor storm drainage system is not subjected to flows greater
than its design capacity, it is required that the Consultant check the total inlet
capacity for the entire system. It is likely that this analysis will determine that
during a major storm, flows greater than that of a 1 in 5 year return period storm
will enter the storm sewer system, and the Consultant will likely need to specify
inlet control devices (ICDs) to limit the quantity of stormwater runoff that gets into
the minor storm drainage system. To streamline the design process, it may be
advisable to calculate the 1 in 5 year flows to each catchbasin using the
appropriate hydrologic methods, specifying an inlet control device for each
catchbasin which limits the flow to approximately that design flow for the 1 in 5
year storm, and apply the flow that the ICD will allow into the system at each
catchbasin, and then calculate the hydraulic gradeline. Contingent upon the
results of hydraulic gradeline analysis, it may be necessary to revise some of the
junctions, or revise some of the storm sewer main diameters to ensure that the
hydraulic gradeline is below the top of the pipe.
85
6.7.1.2 Minimum Pipe Sizes
Storm sewer main diameter shall not be less than 300 mm.
Catchbasin lead diameters shall not be less than 250 mm.
6.7.1.3 Changes in Storm Sewer Main Diameter
Storm sewer main diameter must not decrease in the downstream direction.
Manholes are to be provided where the storm sewer main diameter changes.
6.7.1.4 Minimum Depth
The depth of storm sewer mains, measured from the design grade of the finished
surface to the top of the pipe must be a minimum of 1.5 m.
6.7.1.5 Maximum Depth
The depth of storm sewer mains, measured from the design grade of the finished
surface to the top of the pipe may be a maximum of 6.0 m. However, under
special conditions, if justifiable reasons are given, the maximum depth of storm
sewer mains may be increased so that the depth to the crown of the pipe at any
manhole location shall not exceed 8.0 m.
6.7.1.6 Location
All storm sewer mains and appurtenances shall be located within the street right-
of-way or a municipal service easement owned by the Town of Amherst. All
storm drainage outfalls shall be located within a municipal service easement
owned by the Town of Amherst.
Where future upstream lands naturally tributary to the
drainage area exist, a municipal service easement shall be
provided from the edge of the street right-of-way to the
upstream limit of the subdivision.
The minimum width of a municipal service easement shall be 6.0 m. However,
the actual width shall depend upon the depth and size of any pipe contained
therein such that safe access to the pipe is possible. A travel way shall be
provided within the municipal service easement for access and maintenance
purposes.
6.7.1.7 Manholes
A manhole must be provided on a storm sewer main at any change in diameter,
material, horizontal alignment, vertical alignments, pipe main intersections, and at
the upstream end of a pipe.
Where a storm sewer main diameter is less than 1,500 mm, manhole spacing
86
shall not exceed 120 m. Where a storm sewer main diameter is equal to or
greater than 1,500 mm, manhole spacing will be determined in consultation with
the Town Engineer.
The following criteria shall be used for pipe elevation and alignment in storm
drainage manholes to account for energy losses through the manhole:
-
An invert drop equal to the difference in pipe diameter shall be provided
unless a different drop is determined by appropriate calculations;
-
The crown of a downstream pipe shall not be higher than the crown of an
upstream pipe;
-
An internal drop manhole shall be constructed where the vertical drop
between pipe inverts in the manhole exceeds 1.0 m;
-
The Consultant shall take into consideration energy losses at manholes
during peak flow conditions to ensure that surcharging of the system does not
occur;
-
The minimum internal diameter of a manhole shall be 1,050 mm. The
consultant shall ensure that the internal diameter is adequate to
accommodate all pipe and appurtenances in accordance with manufacturer's
recommendations. Manhole ladders are not required.
6.7.1.8 Service Laterals
All service laterals shall be installed according to the following
provisions:
-
For single-family lots, one storm drainage service lateral is to be supplied to
each existing lot or potential future lot which could be created under the
zoning in effect at the time of approval by the Town of Amherst;
-
A minimum 100mm storm drainage lateral shall be laid at a minimum grade of
1.5% to the limit of the street right-of-way.
6.7.1.9 Catchbasins
Catchbasins shall be installed at the curb of the street and shall be adequately
spaced to prevent excessive water from flowing in the travelled lanes during
storm events corresponding to the design of the minor system. In no case shall
the spacing of catchbasins exceed 90 m.
At intersections, catchbasin locations shall be dependent upon the slopes of
intersecting streets and the alignment of the intersection as required by the Town
Engineer.
All storm catchbasins will have a 300mm sump.
6.7.1.10 Inlet Control Devices
87
Inlet control devices (ICD's) must be provided where there is a risk of surcharging
the minor storm drainage system by storm events that exceed the 1 in 5 year
return period. Typical ICD sizing requirements for medium density residential
development are provided in Table 6.5
Table 6.5
Typical Inlet Control Device (ICD) Sizes
Catchbasin
Tributary Area
(ha)
ICD
Limiting Flow
(L/s)
ICD
Diameter
(mm)
0.1
16
85
0.2
32
120
0.3
48
150
0.4
64
170
Table 6.5 is based on:
1.
a Rational Method runoff coefficient (C = 0.50) for medium density residential
development;
2.
an inlet time (Ti = 5 min) for medium density residential development; and
3.
a head of 1.13m.
6.7.1.11 Inlets
Inlets to piped storm drainage systems shall, for pipes 300 mm in diameter or
larger, require grates to prevent entry. The orientation of the bars on the grate
shall be vertical. The design of the inlet shall take into consideration the effect of
the grating on restriction of flow into the pipe.
6.7.1.12 Outfalls
Design of outfalls from piped storm drainage systems into any receiving body of
water shall take into consideration such factors as public safety, erosion control
and aesthetics.
Outfalls from piped storm drainage systems of 300 mm in diameter and larger
shall require grates to prevent entry. The orientation of the bars on the grate
shall be horizontal. Inverts of outfall pipes should be installed above the normal
winter ice level in the receiving stream wherever possible.
6.7.1.13 Required Pipe Strength
88
Pipe, when installed within the street right-of-way, or a municipal service
easement, shall be either reinforced concrete pipe (RCP) manufactured to
conform to CAN/CSA A257.2, Polyvinyl Chloride Pipe (PVC) pipe to conform to
CAN/CSA B192.1, or as per the Standard Specification for Municipal Services for
Nova Scotia. DVC pipe to be color white.
Required pipe strength shall be determined using the Marston and Spangler
equations, or by nomograph method as published by the American Concrete
Pipe Association for reinforced concrete pipe or the Uni-Bell PVC Pipe
Association for PVC pipe.
Imposed loads should consider the effects of earth load (We), live load (Wl),
surcharge load (Ws), bedding factor (Bf), and pipe diameter (D). A factor of
safety (FS) of 1.5 should be applied when determining required pipe strength.
[6.1]
where:
Dload
required pipe strength
We
earth load
Wl
live load
Ws
surcharge load
Bf
bedding factor
D
pipe diameter
6.7.2
Roads and Intersections
6.7.2.1 Minor Storms
In storms corresponding to the basis of design of the minor drainage system, it is
expected that roadways will remain free of water other than that accumulated
between inlets.
6.7.2.2 Major Storms
For barrier-type curb applications, storm drainage design shall provide that the
depth and spread of flow in a 1 in 100 year return period storm shall be contained
within the right-of-way.
For mountable-type curb applications, the area located directly behind the curb
(
)
D
B
W
W
W
D
f
s
l
e
load
⋅
+
+
=
89
must be graded in order that there be no overflow discharged from the right-of-
way except at municipal service easements designed to convey the overland
flow.
All low points in the roadway profile must be designed to collect and convey
stormwater runoff off the roadway via a drainage easement designed to convey
the overland flow.
Provision shall be made to remove runoff into drainage channels, watercourses,
and pipe systems at low points and at intervals that will assure that this criteria is
observed.
6.7.3
Ditches/Open Channels
6.7.3.1 Design
Roadway ditches, where curb and gutter systems are not required, shall be
designed to conform to the typical cross section for rural roads in accordance
with the Nova Scotia Department Transportation and Public Works Standard
Specification. Ditches shall be designed with adequate capacity to carry the flow
expected from the 1 in 100 year return period storm.
Table 6.9
Manning Roughness Coefficient (n) for Open Channel Flow
Material
Manning
Roughness
Coefficient
(n)
Asphalt
0.013 to 0.017
Brick
0.012 to 0.018
Concrete
0.011 to 0.020
Rubble or Rip Rap
0.020 to 0.035
Lined
Channels
Vegetal
0.030 to 0.400
Earth, straight and uniform
0.020 to 0.030
Earth, curved and uniform
0.025 to 0.040
Rock
0.030 to 0.045
Excavated
Channels
Unmaintained
0.050 to 0.140
Regular section
0.03 to 0.07
Natural
Channels
Irregular section with pools
0.04 to 0.10
6.7.3.2 Maximum Velocity
To prevent erosion, maximum velocities in a 1 in 100 year return period storm in
ditches or open channels that convey stormwater runoff shall not exceed values
set forth in Table 6.6 unless the channel is lined or acceptable energy dissipation
facilities are provided.
90
Table 6.6
Maximum Permissible Mean Channel Velocity
Channel Material
Maximum Permissible
Mean Channel Velocity
(m/s)
Fine Sand
0.45
Coarse Sand
0.75
Fine Gravel
1.85
Earth - Sandy Silt
0.60
Earth - Silty Clay
1.05
Earth - Clay
1.20
Bermuda Grass Lined - Earth - Sandy Silt
1.85
Bermuda Grass Lined - Earth - Silty Clay
2.45
Kentucky Blue Grass Lined - Earth - Sandy Silt
1.50
Kentucky Blue Grass Lined - Earth - Silty Clay
2.15
Sedimentary Bedrock - Poor
3.05
Sedimentary Bedrock - Sandstone
2.45
Sedimentary Bedrock - Shale
1.05
Igneous Bedrock
6.10
Metamorphic Bedrock
6.10
6.7.4
Culverts
6.7.4.1 Minimum Size
Minimum culvert diameter is 450 mm for circular culverts. Minimum culvert width
by height is 450 mm x 450 mm for rectangular culverts. No downstream
decrease in culvert sizing is permitted.
6.7.4.2
Minimum Cover
Minimum cover for culverts under roadways is 500 mm.
6.7.4.3 Maximum Cover
The Consultant may be required to submit pipe strength calculations including
earth loading, line loading, and induced loading, accounting for site conditions
and construction practices.
6.7.4.4 Hydraulic Capacity
Culverts are to be sized to convey instantaneous peak flows with a headwater
depth (HW) to culvert diameter (D) ratio of 1.0 accounting for both inlet control
and outlet control.
91
Culverts located under driveways and roadways are to be designed to
accommodate the 1 in 5 year return period storm, unless otherwise directed by
the Town Engineer.
Culverts located in drainage courses or natural watercourses are to be designed
to accommodate the 1 in 100 year return period storm, unless otherwise directed
by the Town Engineer.
6.7.4.5 Maximum Headwater Depth
Maximum headwater elevation (HW) for both inlet control and outlet control
should be checked relative to adjacent ground surface and adjacent structures
for compatibility. The Consultant may reduce maximum headwater elevations
(HW) for culverts under inlet control by improving inlet hydraulics. Table 6.8
presents entrance loss coefficients (ke) for corrugated steel pipe (CSP).
Table 6.7
Entrance Loss Coefficients (ke) for Reinforced Concrete Pipe (RCP)
Culverts Under Inlet Control
Inlet Geometry
Inlet
Type
Entrance
Loss
Coefficient
(ke)
Projecting from fill (bell end)
1a
0.2
Projecting from fill (square cut end)
1b
0.5
Mitered to conform to slope
2
0.7
Headwall or headwall and wingwalls (bell end)
3a
0.2
Headwall or headwall and wingwalls (square cut end)
3b
0.5
Flared inlet conforming to slope
4
0.5
Headwall or headwall and wingwalls (rounded edge)
5
0.1
Bevelled ring
6
0.25
Table 6.8
ce Loss Coefficients (ke) for Corrugated Steel Pipe (CSP) Culverts Under Inlet
Control
Inlet Geometry
Inlet
Type
Entrance
Loss
Coefficient
(ke)
Projecting from fill
1
0.9
Mitered to conform to slope
2
0.7
92
Headwall or headwall and wingwalls (square edge)
3
0.5
Flared inlet conforming to slope
4
0.5
Headwall or headwall and wingwalls (rounded edge)
5
0.2
Bevelled ring
6
0.25
6.7.4.6
Headwalls
All culverts under roadways are to be equipped with an inlet and outlet headwall,
or some other form of embankment stabilization and erosion control.
6.7.4.7 Outlet Velocity
The maximum culvert outlet velocity is 4.0 m/s. A rip rap splash pad and apron
must be designed to transition the culvert outlet velocity to the mean downstream
channel velocity. Rip rap should be sized in accordance with Equation 6.2.
[6.2]
where:
Dmean
equivalent spherical diameter of rip rap (m)
V
culvert outlet velocity (m/s)
Culvert outlet velocities must not exceed the maximum permissible mean
channel velocities for a given channel material as presented in Table 6.6.
6.7.4.9
Inlet and Outlet Grates
Culverts under driveways and roadways less that 25 m in length shall not
normally require inlet and outlet grates.
Culverts longer than 25 m shall be equipped with inlet and outlet grates.
Inlet grates shall be constructed of vertically oriented bars. Outlet grates shall be
constructed of horizontally oriented bars. Design and sizing of inlet and outlet
grates must account for the restriction in flow created by the grate and blockage.
Under no circumstances shall a culvert be equipped with an outlet grate and no
inlet grate. Generally, the cross sectional area of the inlet grate should be 5 to
10 times the cross sectional area of the pipe. Placement of the grate should be
at least one pipe diameter from the end of the pipe.
6.7.4.10 Culvert Materials
Culverts under driveways shall be as per the Standard Specification for Municipal
Services for Nova Scotia.
Culverts under roadways must be reinforced concrete pipe (RCP).
6.7.4.11 Other Considerations
2
019
.0
V
Dmean
⋅
=
93
Explicit consideration shall be given to public safety, NSDEL regulations, NSTPW
regulations, nuisance, and maintenance implications of ditches, open channels,
and drainage courses.
6.7.5
Stormwater Control Facilities
Investigation of requirements to mitigate the downstream effects of a proposed
development shall be carried out to determine the requirements for and feasibility
of the utilization of a storage facility for stormwater runoff control. If a
determination is made that a storage facility is required, its design shall be
carried out using appropriate methods and sound engineering principles. The
design shall take into consideration various factors including, but not limited to,
watercourse protection, erosion and sediment control, impact on adjacent
property, maintenance requirements, public safety, access, liability, and
nuisance.
Such storage facilities shall be designed to control the peak runoff conditions for
multi-storm events up to the 100 year return period storm.
6.7.6
Municipal Service Easement
No storm drainage is to be carried onto, through, or over private property, within a
subdivision, other than by a natural watercourse, excavated ditch, or minor storm
drainage system. To ensure access to storm drainage systems, a municipal
service easement in accordance with Section 4 of these Guidelines- Easements,
shall be granted to the Town of Amherst in the following cases:
-
Excavated ditches or storm sewers within the boundary of the subdivision;
-
Where a need is identified by the Town of Amherst Engineer to accommodate
future upstream drainage, a municipal service easement shall be provided
from the roadway to the upstream limits of the subdivision;
-
A municipal service easement may be required for excavated ditches or minor
storm drainage systems that are adjacent to and immediately downstream of
the subdivision that are required to ensure proper functioning of the municipal
storm drainage system. A municipal service easement will not normally be
required for a natural watercourse;
-
Where stormwater runoff flows from the subdivision onto adjacent properties
other than in a natural watercourse, a municipal service easement in favour of
the Town of Amherst must be provided by the owners affected;
6.8
Minor Storm Drainage System Connections
6.8.1
Foundation Drains
Foundation drains will normally be connected by gravity to the minor storm
drainage system unless the Consultant determines that surcharging of the
system in a 1 in 100 year design storm will result in basement flooding or
94
foundation damage. The elevation of the lateral at the property line should be
established at least 300 mm above the elevation of the top of the storm sewer
main at the point of connection.
Where a minor storm drainage system does not exist, other options are permitted
as specified in the National Building Code. In using other alternatives, the
National Building Code shall be applicable.
Foundation drains shall not be permitted to discharge to ground surface in such a
way as to direct stormwater runoff to the street surface, walkway, or adjacent
private property.
6.8.2
Roof Drains
Roof drains shall not be connected to storm drains, but shall discharge onto
splash pads at the ground surface a minimum of 600 mm from the foundation
wall in a manner that will carry water away from the foundation wall. Where the
roof area to be drained exceeds 250 square meters, it shall be directly connected
to a storm drainage system.
6.9
Discharge to Adjacent Properties
All storm drainage is to be self-contained within the subdivision limits, except for
natural drainage associated with runoff from undeveloped areas. However,
runoff from within the subdivision must be directed to a natural stream,
watercourse, or storm drainage system owned by the Town of Amherst.
In all cases, concentration and conveyance of stormwater to adjacent properties
outside the subdivision limits is prohibited unless the developer obtains
permission from the adjacent property owners, and private drainage or service
easements are provided.
The grading along the limits of the subdivision shall be carefully controlled to
avoid disturbance of adjacent properties or an increase in the discharge of
stormwater to those properties.
The lot grading design shall provide for drainage from adjacent properties where
no other alternative exists.
The lot grading design shall provide for temporary drainage of all blocks of land
within the subdivision that are intended for future development.
During the design of storm drainage systems, provision must be made for
accommodating natural drainage from adjacent properties by means of an
interceptor swale or other system component.
95
6.10
Analysis of Existing Storm Drainage Systems
It may be necessary to analyze the capacity of existing storm drainage systems,
including storm sewer systems within the Town of Amherst. This may be
required due to the fact that a proposed development is going to increase
stormwater runoff to an existing system, and the existing system needs to be
analyzed to ensure that it will convey the additional flows without any problems.
Where consultants are required to analyze an existing storm drainage system
within the Town of Amherst, the following procedure shall be followed in doing so.
6.10.1 Hydrologic Analysis
Where existing systems are being analysed, it is crucial to determine the peak
stormwater runoff to a given point in a system caused by severe rainfall events
and snowmelt events. Where storage facilities are included in the study, it may
be necessary to determine the hydrograph of the stormwater runoff to a particular
point; that is, the simple instantaneous peak flow will not be adequate to analyse
storage facilities. In determining the stormwater runoff or hydrographs, the
methods as described in Subsection 6.4 shall be used.
In preparing the hydrologic and hydraulic model, it may be necessary to
determine the drainage area to each individual storm manhole and each
individual storm catchbasin. This information should be compiled on a master
drawing of the area being studied with appropriate labels for the areas,
manholes, and catchbasins such that calculations can be easily compared to the
plan. For minor storm drainage systems, ie. storm sewers and catchbasins, the 1
in 5 year return period storm shall be checked for the points of interest. For open
channels, watercourses, and major drains on streets, the 1 in 100 year return
period storm shall be checked for the points of interest.
6.10.2 Hydraulic Analysis
For each component of the existing storm drainage system such as a storm
sewer main, open channel, watercourse, or culvert, the hydraulic capacity of that
portion of the system needs to be determined and compared to the flow
determined from the hydrologic calculations. The following procedures are
accepted by the Town of Amherst Department of Engineering and Public Works
for determining the hydraulic capacity of storm drainage structures.
6.10.2.1 Open Ditches, Channels, and Watercourses
To determine the capacity of open channels, ditches, and watercourses, the
Manning equation may be used where grades are relatively steep, greater than
1%. Where grades are less than 1%, it may be necessary to account for
backwater effects using the energy equation and the direct-step or standard-step
methodologies. This may be accomplished with a water surface profile model as
per Subsection 6.4. Also to be considered in these calculations is the water
surface elevation at the outlet of the ditch, watercourse, or channel.
6.10.2.2 Culverts
96
To calculate the hydraulic capacity of a culvert, the inlet capacity of the culvert
and the outlet capacity should be checked taking into consideration maximum
tailwater elevation at the outlet of the culvert. Also to be checked is the barrel
capacity of the culverts using the Manning equation. In general, the inlet capacity
of the culvert will be the limiting factor in determining the capacity.
6.10.2.3 Minor Storm Sewer System
Minor storm sewer systems consist of storm sewer mains, manholes,
catchbasins, and various inlets and outlets. The capacity of a storm sewer
system shall be checked as follows:
-
Preliminary sizing of pipe diameter assuming full flow conditions for each pipe
in the minor storm drainage system using the Manning equation for the 1 in 5
year return period storm. Manning's roughness coefficients (n) have been
tabulated in Table 6.9. The ratio of the 1 in 5 year design flow (Q5) to full flow
pipe capacity (Qcap) should not exceed 80%.
[6.3]
where:
Q5 1 in 5 year design flow (L/s)
Qcap
full flow pipe capacity (L/s)
-
Where deemed necessary by the Town Engineer, a determination of the
hydraulic gradeline (HGL) for the 1 in 5 year return period storm should be
conducted assuming the actual captured flow (Qc) is 100% of the 1 in 5 year
design flow (Q5). Analysis should account for pipe friction losses, junction
and bend losses, outlet tailwater elevation, and capacity constraints of the
downstream system. HGL profiles may be determined by the standard-step
method, the direct-step method, or acceptable energy equation principles.
The HGL profile should be plotted on the plan and profile drawing to ensure
that the water surface profile is contained the pipe. An elevated HGL may
require a pipe diameter larger that as determined by the Manning equation in
order to avoid surcharging of the minor storm sewer system.
-
Where deemed necessary by the Town Engineer, a determination of the
hydraulic gradeline (HGL) for the 1 in 100 year return period should be
conducted assuming the actual captured flow (Qc) is some percentage of the
1 in 100 year design flow (Q100). The actual captured flow should be the
lesser of the maximum catchbasin inlet capacity, the maximum catchbasin
lead capacity, or the 1 in 100 year design flow (Q100). Analysis should
account for pipe friction losses, junction and bend losses, outlet tailwater
elevation, and capacity constraints of the downstream system. HGL profiles
80
.0
5 ≤
cap
Q
Q
97
may be determined by the standard-step method, the direct-step method, or
acceptable energy equation principles. The HGL profile should be plotted on
the plan and profile drawing to ensure that the water surface profile is at an
acceptable level. The elevated HGL profile should not threaten back-up into
service laterals, or basements.
-
Provision of inlet control devices (ICDs), is an acceptable means of limiting
the actual captured flow (Qc) by the minor system in storm events that exceed
the design capacity of the minor storm sewer system. Design capacity (Qdes)
of the major storm drainage system must account for any additional flow
restricted from entering the minor storm drainage system.
6.10.2.4 Stormwater Detention Structures
Components of a storm drainage system may include man-made storm drainage
detention facilities to reduce the peak flow downstream. The following
procedures shall be used to check the performance of a storm drainage retention
facility:
-
Where deemed necessary by the Town Engineer, a 1 in 100 year return
period, 24-hour duration, storm shall be applied to the watershed, using one
of the applicable models in Section 6.4, and a hydrograph should be
generated to assess the stormwater runoff detention facility performance.
-
Where deemed necessary by the Town Engineer, the storage indication
method shall be used to calculate the outflow from this pond, taking into
consideration the outlet condition (that is, the hydraulic outlet structure of the
pond). The maximum flood elevation of this facility shall be calculated as part
of this work. Where the watershed is mostly urban or developed land, it is
likely that a summer storm will be adequate to check this facility; however, if a
large portion of the watershed is forested or open fields, it may be necessary
to check the facility using a winter storm with snowmelt included in the runoff.
98
STREET SYSTEM
DEVELOPER'S OBLIGATIONS
This section establishes the minimum criteria relating to the design and construction of roads
and streets serving new development in the Town of Amherst. All plans of such works shall be
approved by the Town. These Guidelines do not preclude the use of higher standards, where
required in the design of infrastructure to service new development. The Developer shall
supply and install sub-base and base materials and install a 6m wide x 50mm thick
asphalt driving surface. The Town will install concrete curbing and complete the
asphalt paving when occupancy levels dictate.
REGULATORY STANDARDS
Roads and streets shall be designed and constructed in accordance with the latest revision of
the Nova Scotia Standard Specification for Municipal Services, the Transportation Association
of Canada's Geometric Design Guide for Canadian Roads and the Nova Scotia Department of
Transportation and Public Works Standard Specification for Highway Construction and
Maintenance.
A copy of all Regulatory Agency approvals shall be forwarded/copied to the Town before any
work commences.
Contractors/Developers shall make themselves familiar with the requirements of the Nova
Scotia Standard Specification for Municipal Services before making application to the Town.
DESIGN CRITERIA AND STANDARDS
Street Classification
Roadway classification groups roadways based on the type of service that they provide to the
public. When a roadway is properly classified, the characteristics and "feel" of each roadway
are easily understood. The classification of roadways is based on factors including: land use,
service function, traffic volume, flow characteristics, running speed, vehicle type and
connections as designated in the Municipal Planning Strategy. The classification also
establishes the geometric design criteria for each group of roads, consistent with operational
needs.
99
Table 3.0 - Street Classification System
Locals
Arterials
Design
speed
(km/h)
50
70
70
min.
intersection
spacing (m)
60
60
200
Right-of-way
width (m)
15
18
20
Min
pavement
width**
8m
9.2
10.4
**The minimum paved radius of a cul-de-sac shall be 13.8 meters.
Design Requirements
General Principles
·
Residential streets shall conform to the overall community design intent of the
development.
·
Through traffic on local streets shall be minimized.
·
Street patterns in the new development shall recognize patterns in existing
adjacent developments and shall not detract from the efficiency of these existing
streets.
Pavement Design
The pavement structure of the roadway must reflect the traffic volume on that particular
roadway. Based on the existing silty-sand subgrade material commonly found in the Amherst
area, the minimum thickness of sub-base, base and asphaltic concrete are provided in Exhibit
4.0.
Exhibit 4.0 - Minimum Required Material Thicknesses
for Flexible Pavements
Roadway
Classifica
tion
Sub-Base
Depth
Base Depth
Asphalt
Concrete Depth
100
Local
250 mm
150 mm
75 mm
Collector
300 mm
150 mm
75 mm
Arterial
450 mm
150 mm
100 mm
Note: All Materials and existing subgrade to be compacted to 98% Standard Proctor Density.
Design Criteria
·
Street intersections shall be constructed at between 70 degrees and 110 degrees.
·
Where a proposed public street intersects an existing public street, the minimum sight
distance along the existing public street shall be 65 meters.
·
Maximum longitudinal roadway grades shall be as follows:
- Arterial
4%
- Collector
6%
- Local
8%
.
Minimum longitudinal grade 0.5%