CHAPTER 10
UTILITIES DESIGN
The Public Utilities franchise area for water and sewer is generally co-terminal with the urban and
suburban overlay districts as identified in the City’s comprehensive plan. Contact Public Utilities for
determination.
10.0
GENERAL
A.
Municipal water and/or sewer shall be required to be provided to proposed land
development areas if the cost per lot for extending facilities is equal to or less than
four times the cost per lot of an alternate source (i.e. well and/or septic tank). This
determination shall be made during the predesign process.
This policy will be applied to proposed developments which are not adjacent to
existing water and/or sewer services. The policy will not apply to the development of
unmanned utility facilities as defined in the Zoning Ordinance.
The following procedure set forth in this policy shall determine whether the
developer will be required to extend water and/or sewer to the proposed subdivision
or be allowed to develop alternate facilities (wells and/ or septic tanks).
1.
The total proposed development area, not individual sections, will be
theoretically subdivided into equivalent residential units sized according to
the approved LAND USE PLAN.
2.
An estimate will be made for providing public water and/or sewer to the area.
The estimate will include off-site as well as on-site improvements.
3.
A cost per unit will be determined by dividing the estimate (Item b) by the
number of units (Item a).
4.
The cost of an alternate water and/or sewer system (wells and/or septic tanks)
will be obtained by calling several suppliers of the services needed.
5.
A comparison of the cost per unit for each method of supplying service will
be done. If the cost per unit for the alternate system when multiplied by four
is less than the municipal system estimate per unit (Item 3), then the
installation of water and/or sewer facilities will not be required.
It is recommended that the engineer contact the Department of Public Utilities for
any special conditions that may impact the determination.
B.
Revised 07/01
Testing and installation for all utility facilities which are to become a portion of the
public water and/or sewerage systems must be done in accordance with the applicable
Utilities Design
Page 10 - 1
sections of the Public Facilities Manual (PFM), Vol. II & III.
C.
All Standards referenced shall be the edition current at the time of plan approval.
D.
In the event that the location of lot lines change after the plans have been approved, it
is the responsibility of the developer to relocate water and sewer laterals as necessary
to meet design criteria requirements. This includes abandoning the old services at the
main.
E.
Dead ends shall be kept to a minimum. Additional loops may be required to ensure
water quality will be maintained.
F.
Transition easements are generally not permitted; however, in the event a transition
easement is proposed or required, it shall run in a straight line between the two
rights-of-way it connects.
G.
Miscellaneous:
1.
Generally sewer or water lines shall not be placed underneath sidewalks, curb
and gutter, driveways, etc. Exception would be crossings for a short length.
2.
Placement of water line within right-of-way shall be in such a manner that
operation and maintenance can be performed with relative ease and without
requiring encroachment on private property. Water lines normally are to be
located behind the curb line. Water lines shall not be placed underneath sidewalks, curb and gutter, etc., except for crossings for a short length. Setback
from the edge of an easement or right-of-way line shall be at least one half of
the distance calculated under Section E-1.
3.
Soil borings should be taken and analyzed to determine the corrosiveness of
the soil to ductile iron pipe (not required if ductile iron pipe or fittings are not
used). Testing shall be in accordance with AWWA C-105 Appendix A.
4.
Soil should be analyzed to determine if adequate bearing capacity is
available. Thrust support shall be based on soil bearing capacity. If soil
bearing capacity is less than 3,000 lb/sq.ft., standard thrust block detail TB-1
in PFM Volume II cannot be used.
10.1. SEWER COLLECTION SYSTEM CRITERIA
All Sanitary Sewer Facilities shall be designed in accordance with the Commonwealth of
Virginia Sewage Collection & Treatment Regulations, the City of Chesapeake Standards and
Specifications, Policy and these Criteria.
A.
Gravity Sewer
1.
Revised 07/01
Materials shall conform to PFM, Volume III.
Utilities Design
Page 10 - 2
2.
Excavation, pipelaying, bedding, haunching, backfilling, and tamping shall
strictly conform to the City's Specifications, PFM, Volume III.
3.
Changes in pipe size, slope, and/or material will occur only at manholes.
Where a small sewer joins a large one, the invert of the larger sewer shall be
lowered sufficiently to maintain the same energy gradient. An approximate
method for securing these results is to place the 0.8 depth point of both
sewers at the same elevation.
4.
Maximum distance between manholes for pipe sizes of less than fifteen
inches shall not exceed 400 L.F.
5.
Gravity sewer sizing shall be in accordance with the State Regulations for the
flows generated by the served property, based on the approved LAND USE
PLAN. Minimum size shall be eight inches.
6.
Slope of the gravity sewer shall be kept to a minimum in order to allow the
largest service area possible. (Manning n = .0l3)
Sewer
Size_
8"
10"
12"
*
Revised 07/01
Min. Slope in Feet
Per 100 Feet___
0.40 (0.30 for PVC pipe only)*
0.28 (0.25 for PVC pipe only)*
0.22 (0.l9 for PVC pipe only) *
The Department of Environmental Quality approval is required for the
flatter slopes used with PVC Pipe if the development exceeds 100 units
(based on all phases of the development) or produces greater than 40,000
G.P.D.
7.
Unsuitable material (Class III, Type SM, SC, Class IV soils, per USCS
ASTM D-2387) shall not be used for pipe bedding. When unsuitable
material is encountered pipe bedding shall be VDOT size 57 smooth river
rock. Flexible sewer pipeline design shall consider pipe depth, pipe material,
soils, and dynamic loads. Deflection shall not exceed 80% of the
manufacturer’s allowable maximum or AWWA recommended maximum,
whichever is least.
8.
Gravity sewers with less than three (3) feet of cover shall be ductile iron pipe,
unless otherwise approved in the predesign conference. Truss pipe may be
used for sewers with 30 to 36 inches of cover. Ductile iron pipe shall be used
for sewers with less than 30” of cover. Calculations shall be provided to show
that the pipe design will adequately handle both static and dynamic loads
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Page 10 - 3
Truss pipe or ductile iron pipe shall be used for sewers with greater than
thirteen (13) feet of cover if approved in the predesign conference.
9.
Ventilation shall be provided for any continuous watertight length in excess
of 1000 ft. in length.
10.
Manholes shall be placed at the quarter point or mid point of the road. Pipe
location shall not pass under drainage structures or curb and gutter except for
crossings. Setback from the edge of an easement or right-of-way line shall be
at least one half of the distance calculated under Section E-1.
11.
Gravity sewer that is subject to extension shall terminate in a manhole. A
sufficient length of gravity sewer pipe shall be stubbed out of the manhole
such that a future connection can be made without cutting the pavement. The
sewer stub shall be plugged at both ends. All sewer lines shall terminate in a
manhole, cleanout or inspection box. If the invert is equal to or greater than 5
feet deep, the line shall end in a manhole.
12.
Gravity sewer mains shall be laid at sufficient depth to serve all drains in
existing buildings. The engineer shall check for the existence of basement
drains prior to the design of the gravity sewer system.
13.
Gravity sewer mains shall not be installed deeper than 15 feet from the invert
to the final grade unless a variance has been obtained in the predesign
process.
14.
All manholes shall be equipped with watertight manhole inserts.
15.
Curved sewers are not permitted.
B. Sewer Laterals
Revised 07/01
1.
Acceptable materials for sewer laterals shall be as specified in PFM Volume
III.
2.
At least one (1) sewer lateral shall be provided to each proposed and existing
lot. One (1) lateral shall be provided to each existing dwelling and the lateral
location, both horizontal and vertical, shall be coordinated with the property
owner.
3.
Laterals will extend from the gravity main to the right-of-way line and will be
perpendicular to the gravity main or extended from the manhole on cul-de-sac
lots.
4.
Laterals will be sized in accordance with the rates of flow generated by the
served property. Minimum lateral size will be four inches. Rates of flow are
Utilities Design
Page 10 - 4
available through the Department of Public Utilities
5.
6.
Laterals will be placed five feet from the centerline of the lot (opposite the
water service) for proposed lots. Laterals to existing dwellings shall be
provided and the location coordinated with property owner by the City
inspector during construction.
Laterals will, whenever possible, terminate in unpaved areas.
7.
No laterals will be permitted on transition gravity mains.(i.e. lines not
included in city-maintained streets)
8.
Laterals from sewers more than l3 feet deep shall originate from a manhole in
lieu of the main trunk line whenever possible.
9.
Laterals shall terminate in cleanouts, inspection boxes or manholes at the
right-of-way line. If the depth of the lateral at the right-of-way is greater than
or equal to 5 feet, a manhole shall be used.
C.
Peak Flow - Peak flow design requirements shall be in accordance with current State
Regulations.
D.
Force Mains
Revised 07/01
1.
Materials shall conform to PFM Volume III.
2.
Excavation, pipelaying, bedding, haunching, backfilling, and tamping shall
strictly conform to the City's Specifications, PFM Volume III.
3.
Sub-surface utility warning tape will be placed not less than six inches nor
more than twelve inches below the proposed finished grade and directly over
non-metallic pipe. In streets the warning tape shall be located immediately
below the pavement section. This tape will be bright green and have
"Caution-Sewer Line Below" clearly printed on it.
4.
Tracer wire shall be installed on all non-metallic pressure pipes.
5.
Restrained joint pipe will be used for bridge crossings and ball joint pipe will
be used for buried river crossings.
6.
Two of the following three methods of restraint, thrust blocks, retainer
glands, and/or tie rods will be used at all tees, bends, off-sets, or plugged
ends. Designs shall consider the characteristics of the soil.
7.
A valve with a kicker-joint will be placed at all dead ends.
8.
Force main sizing will be in accordance with the City's Master Sewer Plan
and State Regulations, to carry the flows generated by the design area.
Utilities Design
Page 10 - 5
E.
Revised 07/01
9.
Air release valves are required at all high points on force main lines.
10.
Depth of the force main shall be kept to a minimum.
11.
Thermal expansion/contraction must be addressed in the design stage for all
exposed pipelines.
12.
Whenever a new force main is tied into an existing force main, it shall be
installed such that a valve will be placed on the upstream side of the
connection.
Depth Requirements; Easements; Horizontal/Vertical Clearance; and Location cover shall be defined as the depth from the top of the pipe to the finished grade
(FG).
1
Gravity sewer shall have a minimum cover of 36" in new streets and 48" in
existing streets without curb and gutter.
2.
Laterals will have a minimum cover of 24" at the right-of-way line.
Maximum cover will be 40" at the right-of-way line. Minimum 24" cover is
required under the pavement section. Deeper laterals may be allowed if
approved in the predesign process and adequate justification is provided.
3.
Force mains shall have 36" of cover in new streets or 48" in existing streets
without curb and gutter unless it conflicts with existing or proposed utilities
or storm drain. Every attempt must be made to prevent installation of
pressure mains below gravity lines.
4.
Horizontal distance between sewer mains and water mains shall be a
minimum of ten feet. Horizontal distance between sewer mains and other
utilities, including storm drains, shall be a minimum of five feet.
5.
Vertical clearance between water mains and/or sewer mains and open ditches
shall be eighteen inches (minimum). Consideration shall be given to the
City’s Master Drainage Plan so that future offsets can be avoided.
6.
All sewer lines belonging to the City will be located within the City's rightof-way unless otherwise approved in the predesign process.
7.
All pipelines (gravity and force main) within casings shall be ductile iron
mechanical joint with retainer glands.
8.
Vertical clearance between sewer mains and other utilities, except open
ditches or water, will be a minimum of twelve inches.
9.
The tops of all sewers entering or crossing streams or major drainage features
shall be in accordance with State Regulations. The Department of Public
Works shall be consulted to determine future inverts or improvements to
Utilities Design
Page 10 - 6
streams. (See Appendix 16 for flood elevations). Inverted siphons shall not
be used.
F.
Streams, Estuaries, Lakes and Reservoirs
Crossings and clearances shall be in accordance with current State Regulations and
City Requirements. Inverted siphons shall not be used. (See Appendix 8).
10.2
WATER DISTRIBUTION SYSTEM
All water facilities will be designed in accordance with the Virginia Department of Health
Waterworks Regulations and the City of Chesapeake Criteria, Policy, Standards and Specifications.
A.
Water Mains
1.
Materials shall conform to PFM, Volume III
2.
Excavation, pipelaying, bedding, haunching, backfilling, and tamping shall
strictly conform to the City's Specifications, PFM, Volume III.
3.
Sub-surface utility warning tape shall be placed not less than six inches nor
more than twelve inches below the proposed finished grade or the pavement
section and directly over non-metallic pipe. This tape will be bright blue and
have "Caution Water Line Below" clearly printed on it.
4.
Tracer wire shall be installed on all non-metallic pressure pipe.
5.
Restrained joint pipe shall be used for bridge crossings and ball joint pipe
will be used for buried river crossings. Valves shall be provided at each end
of the crossing. Permanent sample taps shall be provided at each end for
testing the main.
6.
Two of the following three methods of restraint, thrust blocks, retainer
glands, and/or tie rods shall be used at all tees, bends, crosses, off-sets, or
plugged ends. Designs of thrust restraint shall be based on a pressure of l50
psi and shall consider the characteristics of the soil.
7.
A valve with a kicker-joint (not less than 18 feet in length) shall be placed at
the end of a main for future extension. Dead ends should be minimized by
looping of mains. Where dead ends occur, they shall be provided with a fire
hydrant or a blow-off valve assembly. Concrete thrust blocks shall not be
placed at the end of a dead end line, other thrust restraint shall be provided.
a)
Revised 07/01
Four, six and eight inch lines shall be equipped with a two inch blow
off.
Utilities Design
Page 10 - 7
b)
8.
Ten inch and larger lines shall be equipped with a permanent hydrant.
Water main sizing shall be in accordance with the City's Master Plan and
Virginia Department of Health's Water Works Regulations, to provide for
domestic and fire flow demands, (i.e. 25 psi, residual pressure with l,000 gpm
fire flows) and water quality considerations with minimum line size being 4"
except as noted below. Short cul-de-sacs and courts (less than or equal to six
units), may be permitted to use a two (2") inch looped line. Hydraulic
analyses shall be submitted by the engineer to size the proposed water mains.
The analysis shall include existing City mains to insure that service to
existing customers is not to be adversely affected. (NOTE: If fire flows
above those noted here are required by Fire Department, then alternate water
sources shall be provided.)
a)
Water source for analysis shall be an existing line at least ten (l0)
inches in diameter.
b)
Minimum allowable pressure for design purposes shall be 40 psi at
the water meter for non-fire flow conditions.
c)
Headloss in any unlooped mains shall not exceed 20 ft. between tieins to looped main.
d)
Velocity shall not exceed 5 ft. per second in any water main 12" or
larger diameter and 8 ft. per second in mains 10" or smaller diameter.
e)
If fire flows are used as a basis for existing pressures then the residual
pressure shall be used as the basis. The pressure shall then be
adjusted to the design flow of the project.
f)
Fire Flow Demand Calculations – Residential Subdivisions
Subdivision water system improvements shall be designed to provide
a fire flow demand of 1000 gpm plus 3 gpm per equivalent residential
unit with a minimum 25 psi available.
Revised 07/01
9.
Valves will be placed on each intersecting line and be located no more than
three feet from each fitting unless otherwise approved by Public Utilities in
writing. Typically, the number of valves shall be no less than one less than
the number of pipes, however all lines may be required to have valves
installed for operational or maintenance reasons. Valve spacing on long
straight runs of pipe will be determined by Public Utilities Department. Valve
location can be affected by site specific conditions.
10.
No air vent, meter or blow off chamber shall be connected directly to a storm
or sanitary sewer.
Utilities Design
Page 10 - 8
11.
Thermal expansion/contraction must be addressed during the design phase of
the project for exposed pipe.
12.
Joint deflect shall not exceed 80% of manufacturer's recommended maximum
or AWWA maximum, whichever is less.
13.
Casings – Any use of casings must be identified in the pre-design process.
14.
B.
a)
Casings when used shall terminate no less than four (4) feet beyond
the edge of pavement or back of curb.
b)
Casings shall be designed to facilitate removal of a full joint of pipe
from the casing from one end. No fittings, structures, appurtenances,
landscaping, etc. will be permitted within 25’ of this end of the
casing.
c)
A minimum 15’ wide by 25’ long easement and/or right-of-way must
be provided on one end of the casing for pipe removal.
Minimum water main size serving fire hydrants shall be eight (8) inches
except for hydrant branch lines unless otherwise approved in the pre-design
process by the Utility Engineer.
Water Service Lines
1.
Acceptable materials are as specified in PFM Volume III.
Materials presently acceptable for use are copper type "K" tubing for up to
two inch O.D.; for over two inch use same material as acceptable under
Water Main section.
Revised 07/01
2.
At least one service line shall be provided to each proposed and existing lot.
One service line shall be provided to each existing dwelling and the lateral
location will be coordinated with the property owner.
3.
Normally, meter boxes will be placed in the right-of-way between the back of
curb and the sidewalk. If there is no sidewalk, then immediately behind the
back of curb. If there is no curb, then adjacent to the right-of-way line with
the end of service line inside the box. (See standard detail WM-1 in the
PFM, Volume II).
4.
Service lines shall be sized and installed in accordance with City Standards
and State Regulations to provide adequate water flow and pressure to the
property being served. Minimum service line size will be 3/4 inch. Lines
shall be perpendicular to the water main except at the end of a cul-de-sac.
5.
Master meters shall be sized to handle the range and frequency of flows
anticipated for the project.
Utilities Design
Page 10 - 9
6.
C.
Meter and service line requirements shall also be in accordance with the Fire
Protection policy.
Depth Requirements, Easements, Horizontal/Vertical Clearances, and Location.
1.
Water mains shall maintain 36" of cover (48" in existing streets without curb
and gutter). Every attempt shall be made to prevent the installation of
pressure mains below gravity mains.
2.
Water service lines, two inches and smaller, shall have a minimum cover of
24" to 30". Water service lines, greater than 2" shall have a minimum cover
of 30" to 36".
3.
Horizontal distance between water mains and sewer will be a minimum of ten
(l0) feet. When local conditions prevent a horizontal distance of ten feet, the
water line may be laid closer to the sewer line or manhole provided that the
bottom of the water main is eighteen inches above the top of the sewer.
Where this vertical separation cannot be obtained, the sewer shall be
constructed of water pipe meeting AWWA standards, pressure tested in place
without leakage prior to backfilling.
Horizontal distance between water mains and other utilities, except sewer,
will be a minimum of five feet.
4.
Revised 07/01
Vertical clearance between water mains crossing over sewer mains shall be
eighteen inches (water over sewer). When local conditions prevent a
minimum 18" vertical separation between water & sewer, the following
construction shall be used:
a)
Water lines shall pass under sewers only if approved in the predesign
process.
b)
Sewer passing over or under water lines shall be constructed as
described in Utilities Design Criteria, Section C-3c.
c)
Water lines passing under sewers shall, in addition, be protected by
providing:
1)
A vertical separation of at least eighteen inches between the
bottom of the sewer and the top of the water line.
2)
Adequate structural support for the sewers to prevent
excessive deflection of the joints and the settling on and
breaking of the water line.
3)
The length of water line be centered at the point of the
Utilities Design
Page 10 - 10
crossing so that joints shall be equidistant and as far as
possible from the sewer.
5.
10.4
10.5
d)
Vertical clearance between water mains and other utilities, except
sewer and open ditches, will be a minimum of twelve inches.
e)
Vertical clearance between water lines and storm drain pipes will be
twelve inches.
All water mains belonging to the City will be located within the City's rightof-way unless an alternate location in an easement parallel and adjacent to the
right-of-way are approved by the Utility Engineer.
ACCEPTABLE MATERIALS
A.
All materials provided within a project shall be the same Manufacturer for each type
of material installed. Exception: Changes required by site constraints such as depth
or crossings are acceptable.
B.
Only those materials identified in the PFM, Vol. III shall be used for facilities which
are to be incorporated into the public water and/or sewerage system. Utilization of acceptable materials is subject to the limitations identified in any volume of the PFM.
C.
Gravity sewers, force mains and water lines located in transition easements (i.e.
utilities not located within city maintained right-of-way) shall be ductile iron.
EASEMENTS,
LOCATION
A.
HORIZONTAL/VERTICAL
CLEARANCES
&
UTILITY
Easements will be computed as follows:
W = 2d + D + 2 (rounded up to the nearest five feet)
d = depth of pipe (from invert)
D = diameter of pipe (I.D.)
W = width of easement
Minimum easement width will be fifteen feet for a single line.
B.
10.6
Where large meters are installed, the easement shall extend at least 5 feet from all
facilities to be owned by the City.
SEWAGE PUMPING STATIONS
A.
Revised 07/01
General Requirements - All sewage pumping stations will be designed in accordance
with the State Regulations, the City of Chesapeake Standards and Specifications,
Policy, Criteria and OSHA Regulations.
Utilities Design
Page 10 - 11
1.
All below ground structures will be constructed with reinforced concrete and
sized in accordance with the State Regulations for the ultimate design flows.
2.
All above ground structures will be constructed of block with brick veneer
and sized in accordance with City Standards so that the ultimate designed
pumps, motors, controls, piping, etc., are readily accessible for maintenance
and protected from the weather; structural design subject to approval by City
of Chesapeake.
3.
Outside features must include an emergency pump connection, emergency
electrical connection and a driveway of 7" Class A3, concrete with minimum
W5 x W5 wire reinforcing.
4.
Architecture of pumping station which deviates from the City standard shall
be compatible with the neighborhood and is subject to City approval.
5.
A hydraulic analysis shall be performed to determine the effect of the new
facilities on existing City facilities. The analysis shall include as a minimum,
all existing City facilities which may be affected up to the discharge point
into HRSD.
6.
Consideration shall be given in the station design to operational and
maintenance concerns which occur when initial flows are substantially below
ultimate design flow or when prolonged periods of low flow are anticipated.
7.
Pumping stations (except submersible pump stations) shall not discharge into
an existing gravity system.
8.
Portable equipment form shall be submitted along with the construction plans
and provide the following:
9.
Revised 07/01
a)
Overflow time (Minimum overflow holding capacity for the pump
station shall be as directed by Public Utilities in the predesign
process.)
b)
Dominion Virginia Power circuit type (looped or radial) and identification number.
The design shall consider and check the following criteria:
a)
Design flow = 3.1 persons/residence x 100 GPD/capita x 2.5
(peak factor)
b)
Average flow = Design flow/2.5
c)
Detention volume = 10 minute pump cycle fill time x average
Utilities Design
Page 10 - 12
flow/7.48 gal./cu. ft.
10.
11.
Revised 07/01
d)
Wet well volume based on geometric shape.
e)
Head calculations for suction and discharge piping.
f)
Total dynamic head at the design flow.
g)
Pump selection shall consider minimum and maximum TDH
conditions at initial and ultimate design the effects of other pump
stations on the line, pump runout conditions, NPSH required and
HRSD interceptor policy.
h)
Minimum velocities as set forth by the Department of Environmental
Quality.
i)
Siphon head if applicable.
j)
Pumps must alternate.
k)
Ventilation Requirements as set forth by the Department of
Environmental Quality.
l)
Fillets shall terminate no more than 18 inches from the outside of the
suction pipe or inlet.
Service Area and Site Location:
a)
Pumping station service area will have approximately a 3000' radius
centered at the pumping station. The service area shall be proposed
by the engineer and shown on a real estate map and approved by the
Department of Public Utilities prior to station design. Pumping
station shall also be located to take advantage of topography so as to
maximize the reach of the system. The engineer must provide
information on City topo map to ensure that the entire proposed
service area can be served.
b)
Pumping station site location will be in accordance with the City's
Master Sewer Plan and subject to City approval and coordinated with
the Department of Planning.
c)
The site has to be purchased and plat deeded to the City. A typical lot
size is 40' x 55' and it must be adjacent to City maintained right-ofway.
Pump Station drawings shall be drawn to scale in all views.
Utilities Design
Page 10 - 13
12.
B.
Types and Applications
1.
Horizontal (wet well-dry well, flooded suction) type pumping stations are
permitted for any application.
2.
Vertical (suction-lift) type pumping stations are permitted for any application.
3.
Revised 07/01
A copy of the geotechnical report used to design the Pump Station shall be
submitted with the plans.
a)
Initial operating speed shall not exceed l500 RPM.
b)
Ultimate operating speed shall not exceed l850 RPM.
c)
Maximum reprime time shall be 5 minutes.
d)
Ensure the net positive suction head (NPSH) and priming lift are
adequate.
Submersible type pumping stations are permitted to discharge into an
existing gravity sewer system and only when the area to be served cannot be
expanded to pick up additional flows. Prior written permission must be
granted by the Utility Engineer. The selection and use of underground
submersible pumping stations within the City of Chesapeake shall be required
to satisfy all of the following requirements.
a)
Submersible pumping stations will not be permitted in a proposed
development/subdivision and shall be designed to service a fixed
service area with no room for expansion in service capabilities in the
future.
b)
Submersible stations will be permitted in developed areas where the
Utility Engineer determines during the predesign process that the
acquisitioning of land for a pumping station is not feasible for a
conventional suction lift pumping station and community reaction is
unfavorable towards a standard lift pump station.
c)
The submersible pumping station shall be designed not to exceed a
maximum pumping rate of l50 GPM. The minimum pumping rate
shall achieve a self cleansing velocity in the force main from this
pumping station.
d)
The horsepower rating for the pumps and motors for the submersible
pumping station shall be kept to a minimum.
e)
The submersible pumping station shall be designed and constructed in
accordance with the standards set forth by all applicable local, state
and federal regulatory agencies.
Utilities Design
Page 10 - 14
f)
C.
D.
Revised 07/01
The submersible pumping station shall be provided with an adequate
hoisting device, as necessary, based on the size weight and orientation
of the pump.
Controls
1.
Controls will conform to all local building, electrical and fire codes, N.E.C.
Standard Rules of American Institute of Electrical Engineers, Service Rules
and Regulations of Dominion Virginia Power, N.E.M.A. and state fire safety
regulations.
2.
Electrical service riser diagram shall show all connections and sizes.
3.
Control panels will be constructed in accordance with the City's Standards
and Specifications with details shown on the plans.
4.
Control panels within a building will be mounted with the top of the panel
72" to 60" from the floor.
5.
Control panel for submersible or grinder type pumping stations will be in a
weather-tight exterior enclosure mounted on a concrete pad in accordance
with City Standards.
6.
Control circuitry will be 110 volts.
7.
"Murphy" gauges or approved equal will be used for system control.
8.
All electrical items shall be placed inside the pump house except for the
emergency electrical connection and meter.
9.
An electrical floor plan.
Piping and Appurtenances
1.
All interior piping will be ductile iron flanged pipe.
2.
Gate valves will be non-rising stem, wheel-operated (except for influent
valve), resilient seat. Influent valve shall have operating nut. Ensure gate
valve is provided between emergency pump connection and wall.
3.
Check valves will be horizontal swing type with counter-weight.
4.
Each pump will have separate air release lines that run along wall, and extend
3" below low water level. An inverted check valve is required for wet welldry well application.
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E.
Revised 07/01
5.
Piping will be sized for the ultimate design flows.
6.
Last run of pipe on gravity sewer line entering the station shall be ductile
iron. There shall be 2' minimum between outside wall and first joint of the
ductile iron for both effluent and influent lines.
7.
Submergence of the pump intake shall be adequate to prevent vortexing.
8.
An approved back flow preventer shall be provided for the water service.
Miscellaneous
1.
Air bubbler lines will be encased with PVC tubing and run along wall in an
accessible location.
2.
Heaters will be of forced air heat type with thermostat (for vertical and
horizontal pumping station applications) directed on pumps.
3.
System control gauges will be connected with type K copper tubing.
4.
Junction boxes for submersible pumping station will be installed inside valve
pit.
5.
Pressure and vacuum gauges shall be provided.
6.
Float hangers and all miscellaneous metal will be either 6061-T6 aluminum
or stainless steel.
7.
Access hatches for the wet wells will have twelve 3/4" holes drilled into each
hatch.
8.
Pump shall operate at or below the rated horsepower for the motor, for the
entire range of operating conditions.
9.
Ventilation system is provided with calculations to ensure 30 air changes per
hour. Cycle of air must be such that fresh air is made available at area where
maintenance crews would be working. Ducts shall be PVC except vent pipe
above slab, which must be ductile iron.
10.
The high water alarm shall be placed along wall and in an accessible location.
11.
A removable bar screen shall be installed at the influent line.
12.
Interior of the pump station wetwell shall be treated to prevent corrosion.
(Sikacoat basecoat Sika 124 and finish coat Sika 62 or approved equal)
13.
All pump stations shall be equipped with 3-phase power.
14.
Soft start motors shall be used on all pumps above 20 hp.
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15.
10.7
480 volt, 3 phase motors shall be used for 40 hp. And above.
F.
All necessary drawings to insure a complete pump station project shall be included
with the plans.
G.
All new pump stations shall be designed in such a manner as to allow for the
installation of a fixed generator. A generator is not required as part of the initial
installation unless adequate response times are not available as required by
Paragraph F.1.h.1 above.
1.
Adequate space shall be provided to insure that any necessary control
cabinets (e.g. transfer switches, switchgears, etc.) can be installed with the
pump station in accordance with applicable laws, codes, and regulations
without the relocation of any existing equipment.
2.
The construction of the pump station shall be made for any necessary
connecting conduits for the future installation of the generator with
necessary caps or closures placed over the ends of the conduit.
3.
The pump station lot shall be sized and laid out to allow for the installation
of an external generator in accordance with all applicable laws, codes, and
regulations.
WATER METERS
A.
All continuous demands should not exceed thirty (30%) percent of the AWWA
recommended maximum rate capacity for the size and type of meter to be used.
B.
Peak design demands shall not exceed eighty (80%) percent of the AWWA
maximum rated capacity for the size and type of meter to be used. This allows for
future minor increases without increasing meter size.
C.
measured.
Meter shall be sized to ensure that expected range of flow conditions will be
Acceptable flow ranges shall be as identified in AWWA standards.
D.
10.8
Detector check meters may be used for fire systems only. For combined fire and
domestic water systems, approved combination meters shall be used.
Activations
Prior to activation, the following items must be provided to Public Utilities. Upon receipt of
these items, the new facilities will be incorporated into the public systems following an
inspection of the facilities showing no defects.
A.
One (l) Year Defect and Maintenance Bond
B.
Deed of Dedication of Utilities
C.
Affidavit of No Dues
Revised 07/01
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10.9
D.
Cost of Utility Improvements
E.
Telemetry and Standby Pump Deposit
F.
Construction Record Drawings (Mylar)
G.
Statement of Completion from Public Works
H.
Certificate To Operate from the Virginia Department of Environmental Quality
(sewer only)
I.
All required easements and plats must be recorded.
J.
Statement of Completion for on-site utilities with bacteriological sample results
K.
Cross Connection Inspection
L.
Pro Rata Payment
M.
Statement of Responsibility
N.
VDH/DEQ Approval
UTILITIES PRO-RATA
Any off-site City utility improvements installed by a Developer that satisfy the conditions set
forth in the Chesapeake City Code, Section 70-123, may qualify the Developer for pro rata
participation.
In addition, a Developer may be required to pay his pro rata share of the cost of utility
improvements installed by previous Developers in accordance with Chesapeake City Code,
Section 70-123
It is suggested that the Developer contact the Public Utilities Department during the
predesign process if more information is desired.
10.10 CROSS-CONNECTION CONTROL
State law and City ordinance require that the public water system be protected from the
backflow into the water system. In order to comply with these requirements, Public Utilities
has adopted a policy for controlling cross connections. For information on potential
requirements for a project, contact the Cross-Connection Inspector.
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