These regulations are set forth to ensure clarity
as to the submission of all data deemed essential for comprehensive
consideration of the contemplated project, and to establish the minimum
standardized basic design criteria considered necessary to provide
facilities which will be designed in accordance with good engineering
practices.
[Amended 4-13-2004 by Ord. No. 04-07]
A. Design capacities.
(1) In general, sewer lines shall be designed for the
estimated contributory population to be served in the future, plus
adequate allowance for infiltration, institutional and industrial
flows for the basin as defined by the Department of Public Works.
(2) Provisions shall be made to extend sewer service to
all adjoining properties, parcels or lots, regardless of ownership
or control of adjoining properties, parcels or lots.
(3) The maximum hourly quantity of domestic sewage, maximum
hourly quantity of domestic sewage and waste from industrial plants
and groundwater infiltration shall be considered in determining the
capacities of sanitary sewers.
(4) The design of extensions to existing sanitary sewage
collection systems shall be based on data if adequate records have
been kept. In the event that adequate records are not available, or
when new systems are being established, the design criteria shall
not be less than 250 gpd per equivalent dwelling unit (EDU) or 175
gpd per mobile home berthing space.
(5) Laterals and minor sewers shall be designed, when
flowing full, assuming flow equivalent to three times the average
daily flow. Main sewers and outfall sewers shall be based on the following
equation:
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Qmax/Qavg = (20+2 [EDU/10]1/2)/(5+2 [EDU/10]1/2)
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where:
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Qmax = Maximum rate of sewage flow
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Qavg = Average daily sewage flow
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(6) Main sewers and outfall sewers shall be designed at
minimum slope and maximum depth.
B. Design details.
(1) No sewers other than building sewers shall be less
than eight inches in diameter. Building sewer laterals located in
the sewer easement or public road right-of-way shall be a minimum
of six-inch diameter with a vertical cleanout riser of four-inch minimum
diameter located at the property line. Cleanout covers shall be cast
iron or brass.
(2) All sewers shall be designed and constructed with
hydraulic slopes sufficient to give mean velocities when flowing full
or half-full of not less than 2.0 feet per second as calculated with
a Manning N of 0.012 for PVC piping and 0.014 for ductile iron piping.
(3) In general, grades which will produce velocities in
excess of 10 feet per second will be considered as unacceptable
(4) Sewers 24 inches or less must be laid in straight
alignment with uniform grade between manholes. For larger pipes, where
horizontal curvature must be utilized to serve a particular area,
the smallest radius of curvature shall be 200 feet, with the Public
Works Director's approval.
(5) Sewers shall be designed deep enough so as to prevent
freezing and pipe failure. Three feet is the minimum cover depth for
normal design conditions.
(6) Manholes shall be placed at the points of all changes
in alignment, grade or size of sewer, intersection of sewers, junction
of streets, and at a distance not greater than 400 feet for sewers
15 inches or less in diameter. Not more than five-hundred-foot spacing
shall be allowed for pipes 18 inches or greater in diameter.
(7) Manholes should be designed large enough to provide
easy access to the sewer. The clearance opposite the steps should
be sufficient for a man to pass through without difficulty.
(8) No manhole shall be located in gutters and ditches.
Manholes in the low spots in the roads should be provided with watertight
covers. No drop manhole or lamp holes shall be used without authorization
of the Kent County Department of Public Works, Engineering Division.
All manholes shall be provided with inserts/bowls to mitigate inflow.
(9) A drop manhole should be provided for a sewer entering
a manhole at an elevation of 24 inches or more above the manhole invert.
If the drop is less than 24 inches, the invert should be filleted
to prevent the deposit of solids. Drop manholes should be constructed
with an inside drop pipe and utilize a minimum of a five-foot diameter
manhole. A "T" shall be used at the top of the drop pipe with the
drop pipe connected to the branch and the end provided with a removable
cap. The drop pipe shall be secured to the interior wall of the manhole
at three-foot intervals and the flow directed into the flow channel
with a suitable elbow.
(10)
Watertight manholes are required at all times.
(11)
Manholes shall be of the precast concrete or
poured-in-place concrete type. Manholes shall be waterproofed on the
exterior with a bituminous coating. Inlet and outlet pipes shall be
joined to the manhole with a gasketed flexible watertight connection
or any watertight connection arrangement that allows differential
settlement of the pipe and manhole wall to take place. Connections
to existing manholes shall be made utilizing a hole saw and a tycite
adapter with A-lok gaskets or link seals.
(12)
The use of inverted siphons shall be kept to
a minimum; but, where they must be used, they shall consist of at
least two lines, one of which will be of a size of not less than eight
inches in diameter. The minimum velocity used in their design shall
be three feet per second considering the average dry weather flow.
Under the minimum dry weather flow conditions, the independent operation
of one of the lines shall provide the minimum velocity of three feet
per second. Where the above conditions cannot be met, some other means
shall be provided.
(13)
Clearances between sewers and other utilities,
both existing and proposed, should be designed as follows:
(a)
Sewers crossing water mains. Sewers shall have
a minimum clearance of 18 inches measured from the outside of the
water main to the outside of the sewer. This shall be the case whether
the water main is above or below the sewer. Where possible the sewer
shall be beneath the water main. The crossing shall be arranged so
that the sewer joints will be equidistant and as far as possible from
the water main joints. Where a water main crosses under a sewer, adequate
structural support shall be provided.
(b)
Sewer parallel to water main. Sewers shall be
kept at least 10 feet horizontally from any water main as measured
from the outside of the water main to the outside of the sewer. In
cases where it is not practical to maintain a ten-foot separation,
the Kent County Department of Public Works, Engineering Division,
may allow deviation on a case-by-case basis if supported by data from
the design engineer or surveyor. Such deviation may allow closer separation,
provided that the water main is in a separate trench or undisturbed
earth shelf located on one side of the sewer and at an elevation so
the bottom of the water main is at least 18 inches above the top of
the sewer.
(c)
If sewer and water main cannot be built to specified
clearances, the sewer shall be designed and constructed equal to the
water pipe and shall be pressure tested to assure water-tightness
prior to backfilling.
(d)
Crossing other utilities. Sewers shall have
a minimum of twelve-inch clearance from drains, electric lines, gas
mains, etc.
(e)
Concrete encasement shall be considered where
the required safe supporting strength cannot be obtained by other
bedding methods.
C. Flow measurement. A Parshall flume with electronic
transducer type flowmeter shall be provided on gravity discharges
from a contract user or from a sanitary district into the County conveyance
system at a point where it discharges into a different sanitary district,
a municipal system or a County pumping station. A flowmeter may be
waived by the Public Works Director for contract users if water billing
or potable water flow measurement is provided and the user and County
mutually agree to use potable water flow for wastewater billing purposes.
The flowmeter shall provide flow totalization and digital instantaneous
flow rate in gpm. If the flume is located in a metering pit, the floor
shall drain to the flume. The totalizer shall be located above ground
in a suitable enclosure to protect it from the weather.
[Amended 6-24-2003 by Ord. No. 03-12; 6-28-2005 by Ord. No.
05-08; 8-10-2010 by Ord. No. 10-13]
A. In accordance with Title 9, Chapter
46 of the Delaware Code, the creation, extension or modification of a sanitary sewer district (SSD) is committed to the sound discretion of Levy Court. Such creation, extension or modification may be initiated by a petition signed by a majority of the property owners affected. The creation, extension or modification of a SSD shall comply with applicable funding agreements, already in place or required to accomplish the action. The creation, extension or modification of a SSD shall not modify the existing Kent County Growth Zone Overlay District boundaries as depicted in the most recently adopted Kent County Comprehensive Plan and Zoning Map.
[Amended 1-15-2019 by Ord. No. 19-01]
B. Sanitary sewer districts (SSDs) may be created, extended or modified
for the purpose of elimination of existing on-site septic systems,
provided that Kent County Levy Court subsequently authorizes the filing
of a funding application and freezes the sanitary sewer impact fees
at the time of creation, extension or modification. In addition, 60%
of the property owners of the proposed area must agree to the creation,
extension or modification via petition.
[Amended 1-15-2019 by Ord. No. 19-01]
C. Outside the Kent County Growth Zone Overlay District, sanitary sewer districts (SSDs) may be created, extended or modified when all requirements of §
180-21B are met or if one of the following conditions are met:
[Amended 1-15-2019 by Ord. No. 19-01]
(1) A property has a failing septic system and a replacement system is
unable to be accommodated; or
(2) A property has been annexed into a municipality in accordance with
its certified comprehensive plan where the municipality is currently
served by the Kent County sewer system; or
(3) A property is located in an area designated as an employment center,
commercial area, or industrial area on the "Land Use Strategies Map"
of the most recently adopted Comprehensive Plan; or
(4) Levy Court by majority vote has determined that extension of Kent
County Sanitary Sewer Service to a particular area or particular areas
outside the Growth Zone Overlay District would be of significant public
benefit.
D. A petition for the creation, extension, or modification of any SSD
shall be submitted to the Kent County Levy Court by the Department
of Public Works. The Kent County Levy Court shall forward the proposed
creation, extension or modification requests to the Kent County Regional
Sewer Advisory Board for review, evaluation, and recommendation for
approval, denial or modification. A public hearing before Levy Court
shall be held on the recommended action, and the final decision shall
be made by Levy Court.
[Amended 1-15-2019 by Ord. No. 19-01]
E. Unless waived at the discretion of the Public Works Director, all requests to extend or otherwise modify the boundaries of any sanitary sewer district will require that the Public Works Department - Engineering Division prepare a technical feasibility study (TFS). Costs for the preparation of the TFS are detailed in Chapter
128 of the Kent County Code. The TFS will include, at a minimum, a hydraulic analysis of the impact of the creation, extension or modification, over the next five years, for the following items:
(1) The pumping station and/or gravity sewer collection system servicing
the area of Kent County Sewage Disposal District No.1 in question,
and all pipelines associated therewith.
(2) All pumping stations, gravity-flow collection systems and associated
pipelines which are downstream of the pumping station or gravity-flow
collection system servicing the sanitary sewer district in question.
(3) Any other potentially adverse flow or pumping conditions which may
be encountered as a direct result of the creation, extension or modification.
F. The findings of the TFS are valid for a maximum period of five years from the date of the applicant's written acceptance of the TFS. If no physical sanitary sewer improvements or direct financial contributions to the same have occurred within the five-year period, then the TFS shall be deemed null and void. The Kent County Department of Public Works shall officially notify the applicant of the expiration date of the TFS. If the TFS is deemed null and void, the applicant is required to reapply for another TFS within three months of being notified of the TFS expiration, as described in §
180-21E. If a response or new TFS request is not received from the applicant, the Department of Public Works may initiate SSD dissolution activities.
[Amended 1-15-2019 by Ord. No. 19-01]