Title 16 PUBLIC WORKS DESIGN STANDARDS
Chapter 16.04 SANITARY SEWERS
16.04.010 General design requirements.
16.04.011 Pipe materials and size.
16.04.012 Minimum design criteria.
16.04.020 Alignment and cover (Reserved).
16.04.021 Right-of-way location.
16.04.022 Minimum cover.
16.04.023 Separation with water lines.
16.04.024 Easements.
16.04.025 Relation to watercourses.
16.04.030 Structures (Reserved).
16.04.031 Manholes.
16.04.032 Cleanouts.
16.04.033 Anchor blocks.
16.04.034 Water bars.
16.04.040 Service lateral.
16.04.050 Connection to existing sewers.
16.04.060 Private sewer lines.
16.04.070 System testing.
16.04.080 Sewage pump station design standards (Reserved).
16.04.081 General.
16.04.082 Construction.
16.04.083 Capacities.
16.04.084 Hydrogen sulfide.
16.04.085 Electrical.
16.04.086 Materials.
16.04.087 Additional features.
16.04.088 Operating and maintenance data.
16.04.090 Erosion control.
16.04.010 General design requirements.
A. Performance Standards. Sanitary sewer system design shall meet the
policies and guidelines of the current Oregon Administrative Rules (OAR), and
the Oregon Department of Environmental Quality (DEQ) guidelines.
B. Sanitary
sewer systems shall be designed to provide gravity service to all areas of
development where public. Pump stations are acceptable only if it is possible to
provide gravity service.
C. Sanitary sewers shall be designed for ultimate
development density of the tributary area. The system shall allow for future
system extension and for future development.
D. Sanitary sewers shall be
designed to remove the domestic sewage and industrial wastes from basements of
houses, where practical, commercial or industrial buildings, and all public and
private establishments where possible.
E. Stormwater, including street, roof
or footing drainage, shall not be discharged into the sanitary sewer system, but
shall be removed by a system of storm drains or by some other method separate
from the sanitary sewer system.
F. Unpolluted or noncontact cooling waters
shall not be discharged into sanitary sewers. The overflow drains and filter
backwash lines of swimming pools and “hot tubs” shall drain into a
sanitary sewer.
G. As a condition of sewer service, all developments will be
required to provide public sewers to adjacent upstream parcels in order to
provide for an orderly development of the drainage area. This shall include the
extension of sewer mains in easements across the property to adjoining
properties and across the street frontage of the property to adjoining
properties when the main is located in the street right-of-way. This shall
include trunk sewers that are oversized to provide capacity for upstream
development.
H. All sewer service lines shall be extended a minimum of ten
feet beyond the last property served within the subdivision.
I. All sewer
lines shall be located within the public right-of-way as directed by the public
works director. These lines are placed in the public right-of-way for ease of
maintenance, access, control of the facility, operation of the facility, and to
provide required replacement and/or repair.
J. Where sewers are constructed
on slopes greater than twenty percent, in areas designated as hazardous or where
there are site conditions that may cause damage to improvements, slippage or
slides as determined by the public works director, a soils and/or geologic
report may be required.
K. Where the finished graded surface is greater than
twenty percent, or as required by the public works director, soil stabilization
fabric shall be placed over the entire disturbed area.
Note: Standard
specifications and drawings relevant to this section may be found in the most
current edition of the APWA Standard Specifications for Public Works
Construction, Oregon Chapter. (Ord. 571 § 1 Exh. A (part), 2005)
16.04.011 Pipe materials and size.
A. All public sanitary sewers shall be constructed with PVC or HDPE pipe
as specified in the appropriate section of the Canyonville standard
specifications. Where required for added strength, epoxy-lined ductile iron pipe
may be used. PVC pipe and fittings shall conform to ASTM D--3034, SDR
35.
B. Private sanitary sewers shall meet the appropriate sections of the
Uniform Plumbing Code (UPC).
C. All sanitary sewer main lines shall be a
minimum diameter of eight inches. Six-inch diameter sewer for nonextendible
sewers of up to two hundred fifty feet in length serving eight lots or less may
be permitted with approval. (Ord. 571 § 1 Exh. A (part), 2005)
16.04.012 Minimum design criteria.
A. Velocity. All sanitary sewers shall be designed on a grade which
produces a mean velocity, when flowing half-full, or full, of no less than two
feet per second.
B. Manning Equation. When calculating minimum pipe slopes
and velocities, the engineer shall use the Manning pipe friction
formula.
C. Pipe Coefficient. The minimum pipe roughness coefficient for
sanitary sewers shall be 0.013. (Ord. 571 § 1 Exh. A (part),
2005)
16.04.020 Alignment and cover (Reserved).
(Ord. 571 § 1 Exh. A (part), 2005)
16.04.021 Right-of-way location.
A. Sanitary sewer lines shall be located five feet north and west from the
right-of-way centerline. All changes in direction of pipe shall be made at a
manhole.
B. Sewers shall be located in the street right-of-way. If streets
have curved alignments, the center of the manhole shall not be less than six
feet from the curb face on the outside of the curve nor the sewer centerline
less than six feet from the curb face on the inside of the curve.
C. Curved
alignments in sanitary sewers are not permitted. (Ord. 571 § 1 Exh. A
(part), 2005)
16.04.022 Minimum cover.
A. All sanitary sewers shall be laid at a depth sufficient to drain
building sewers, to protect against damage by frost or traffic, and to drain
basement sewers, where practical. Sufficient depth shall mean the minimum cover
from the top of the pipe to finish grade at the sewer alignment. In new
residential hillside subdivisions, mainline and lateral sewers shall be placed
in the street at a depth sufficient to drain building sewers on the low side of
the street.
B. Sanitary sewers in residential areas shall be placed in the
street with the following minimum cover:
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Building service lateral
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six feet
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Trunk and collector sewer in the roadway
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eight feet
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In easements
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eight feet
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C. Where pipes cross under ditches or streams and the cover is less
than three feet, extra protection will be required as discussed in Section
16.04.025 of this chapter.
D. Where the topography is relatively flat and
existing sewers are shallow (five feet or less), the minimum cover shall be
three feet.
E. Deviation from the above standards will be considered on a
case-by-case basis when one of the following circumstances
exists:
1. Underlying Rock Strata. Required: A request in writing to the
public works director together with submittal of a soils report with a plan and
profile certifying that bedrock exists three feet below the undisturbed ground
surface at all investigated alignments;
2. A ditch or stream must be
crossed. Required: A plan and profile; horizontal scale 1” = 20’,
vertical scale 1” = 2’;
3. Where three feet of cover is not
possible, the sewer line shall be epoxy-lined ductile iron;
4. A pumping
station may be substituted with approval of the public works director. (Ord. 571
§ 1 Exh. A (part), 2005)
16.04.023 Separation with water lines.
Mains shall be installed a minimum clear distance of ten feet horizontally
from water lines and shall be installed to go under water lines with a minimum
of eighteen inches of clearance at intersections of these pipes. The public
works director shall first approve exceptions. In all instances the distances
shall be measured edge to edge. The minimum spacing between water mains and
storm drains, gas lines, and other underground utilities, excepting sanitary
sewers, shall be three feet horizontally when the standard utility location
cannot be maintained. (Ord. 571 § 1 Exh. A (part), 2005)
16.04.024 Easements.
A. Sewers placed in easements along a property line shall have the
easement centered on the property line and the sewer shall be offset eighteen
inches from the property lines. For sewers placed in easements located other
than along a property line, the sewer shall be placed in the center of the
easement. The conditions of the easement shall be such that the easement shall
not be used for any purpose, which would interfere with the unrestricted use for
sewer main purposes. Under no circumstances shall a building or structure be
placed over a sanitary sewer main or sewer easement. This shall include
overhanging structures with footings located outside the easement. Further, no
trees or large bushes shall be planted in the easement.
B. Easements for
sewers less than twelve inches in diameter shall have a minimum width of fifteen
feet. Sewers greater than twelve inches in diameter shall have a minimum
easement width of twenty feet.
C. Sewers with more than eight feet of cover
and/or inside diameters twenty-four inches or greater will require wider
easements. A slope of one horizontal to one vertical from the sewer invert to
ground surface will be used to determining easement width. Easement widths shall
vary from the fifteen-foot minimum by five-foot increments; for instance,
fifteen, twenty, twenty-five feet.
D. Easement locations for public sewer
mains serving a PUD, apartment complex, or commercial/industrial development
shall be in parking lots, private drives, or similar open areas which will
permit unobstructed vehicle access for maintenance by city personnel.
E. All
easements must be furnished to the city for review and approval prior to
recording. (Ord. 571 § 1 Exh. A (part), 2005)
16.04.025 Relation to watercourses.
A. Generally, the top of all sanitary sewers entering, crossing or
adjacent to streams, irrigation ditches or drainage ways shall be at a
sufficient depth below the natural bottom of the waterway to protect the sewer
line. One foot of cover is required where the sewer is in rock, three feet of
cover is required in other materials. In paved channels, the top of the sewer
line shall be placed at least six inches below finish grade of the bottom of the
channel, except as provided above. Sewers located along streams shall be located
outside of the streambed and sufficiently removed therefrom to provide for
future possible stream channel widening. All manhole covers shall be watertight,
at or below the one hundred-year flood elevation.
B. Sewers crossing streams
or drainage channels shall be designed to cross the stream as nearly
perpendicular to the stream channel as possible and shall be free from change of
grade. The minimum cover shall be thirty-six inches from the bottom of the
streambed or drainage channel.
C. Pipe material shall be ductile iron with
an eighteen-foot length of pipe centered on the stream or drainage channel
centerline. The ductile iron pipe shall extend to a point where a one-to-one
slope, which begins at the top of the bank and slopes down from the bank away
from the channel centerline, intersects the top of the pipe.
D. A scour pad
centered on the sewer line will be required when the top of the pipe to the
bottom of the stream or drainage channel is thirty inches or less. The scour pad
shall be concrete, six inches thick and six feet wide, reinforced with number
four rebar twelve inches on center both ways and shall extend to a point where a
one-to-one slope, that begins at the top of the bank and slopes down from the
bank away from channel centerline intersects the top of the pipe. Each deviation
from the above requirements will be reviewed on a case-by-case basis. (Ord. 571
§ 1 Exh. A (part), 2005)
16.04.030 Structures (Reserved).
(Ord. 571 § 1 Exh. A (part), 2005)
16.04.031 Manholes.
A. Manholes shall conform to ASTM C--478.
B. Manholes shall be located
at changes in slope, alignment, pipe size, and at all pipe junctions with
present of future sanitary sewers.
C. Manhole spacing shall not be greater
than four hundred feet.
D. The angle between incoming and outgoing sewer
lines shall be greater than eighty degrees.
E. Designs for manholes are
shown in the standard drawings. They are suitable for most conditions. New
designs or revisions should not be shown on the construction drawings unless the
standard designs are not suitable. New or revised designs may be necessary
if:
1. One or more of the sewers to be connected to the manhole is over
thirty-six inches in diameter. Smaller diameters may require a special design if
the manhole is at an alignment change.
2. Several sewers will be connected
to the manhole.
3. There is less than eighty degrees between the incoming
and outgoing sewer.
4. The manhole will be subject to unusual structural
loads.
5. Diversion or other flow control measures are
required.
F. Where one or more of conditions 1, 2, or 3 of subsection E of
this section, are encountered, a drawing of the manhole base should be made to
determine if it is feasible to use designs shown in the standard drawings. It
may be necessary to restrict the options to a specific standard drawing
specified by a note on the construction drawings. If a special design is
required for any reason, it will be necessary to the details on the construction
drawings and to provide structural calculations as needed.
G. Some alternate
manhole features are shown in the standard drawings. Where these features are
required, a note on the construction drawings must specify them. Some examples
are:
1. Flat tops must be used in lieu of cones where there will be less
than four feet between the manhole shelf and the top of the
manhole.
2. Watertight manhole frames and covers are to be used if
floodwaters are expected to cover the manhole top or if the manhole must be
located in the street gutter. Such conditions should be avoided wherever
feasible.
3. Tamper-proof manhole frames and covers are required in areas
subject to vandalism, such as areas which are not readily visible to the general
public or the property occupants.
H. Standards for elevation differences at
manholes have been established to compensate for normal energy losses and to
prevent surcharging of a sewer by a larger sewer. For purposes of slope
calculation and for establishing elevation differences, the elevations are given
at the intersection of the sewer centerline (usually the center of the manhole).
The rules for elevation differences at manholes are:
1. The crowns of
incoming sewers shall be at least as high as the crown of the outgoing
sewer.
2. If the incoming and outgoing sewers are of equal size and are
passing straight through the manhole, no added elevation change is
required.
3. If sewers intersect or the alignment changes at the manhole,
the invert elevation difference shall be at least 0.10 feet or ten degrees to
forty-five degrees of horizontal deflection angle, and 0.20 feet for over
forty-five degrees of horizontal deflection angle.
4. The slope of a sewer
within a manhole shall be no less than the slope of the same sewer outside of
the manhole.
5. Where the difference between the slope of the incoming and
outgoing pipe is greater than six percent, the slope across the manhole shall be
the average of the incoming and outgoing pipes.
6. Drop connections are
required when the vertical distance between flow lines exceeds two feet. The
diameter of the drop connection must be specified on the construction drawings.
The diameter of the drop connection shall be not more than one pipe size smaller
than the diameter of the incoming sewer. Smooth flow lines with vertical
distances of less than one foot must be provided wherever feasible. Drop
connections shall be outside drops.
7. All connections must enter the
manhole through a channel in the base. This includes drop connections and
connections to existing manholes.
I. Where conditions make compliance with
these rules impractical, exceptions will be permitted. It will be necessary,
however, for the designer to provide a complete analysis of the need for such
designs. (Ord. 571 § 1 Exh. A (part), 2005)
16.04.032 Cleanouts.
A. Cleanouts will not be approved as substitutes for manholes on public
sewer lines. Cleanouts are permitted at the upper end of a sewer that will be
extended during a future construction phase. When the sewer is extended, the
cleanout will be removed and a manhole shall be installed in the appropriate
location. If future extension requires a change in sewer alignment or grade, a
manhole will be required at the cleanout location.
B. Cleanouts are
permitted at the end of a nonextendable sewer line that does not exceed two
hundred fifty feet in length nor serve more than eight lots. (Ord. 571 § 1
Exh. A (part), 2005)
16.04.033 Anchor blocks.
For sewer pipes greater than four inches in diameter, concrete anchor
blocks shall be required if the slopes are greater than twenty percent. Anchor
blocks shall key into trench sides. Spacing for anchor blocks is as
follows:
SPACING FOR ANCHOR BLOCK FOR ALL SIZE PIPE
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Slope %
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Minimum Spacing (Ft)
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0--19.99
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no anchor required
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20--34.99
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35
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35--50.99
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25
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51 or more
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15 or special design
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(Ord. 571 § 1 Exh. A (part), 2005)
16.04.034 Water bars.
Where the finished graded surface has a slope greater than or equal to
three units horizontal to one unit vertical or as required, water bars shall be
installed. The water bars shall be sloped slightly to drain runoff water away
from the pipeline alignment. Water bars shall have a maximum spacing of forty
feet. (Ord. 571 § 1 Exh. A (part), 2005)
16.04.040 Service lateral.
A. Service laterals are those public sewer lines to which a private
building sewer connects. Service laterals are to be built to the same
construction standards and of the same materials as the sewer
mainline.
B. Each individual building site shall be connected by a separate
private building sewer service line connected to the public sewer. Combined
sewer service lines will be permitted only when the property cannot legally be
further divided. An example of this is a residential lot with a house and an
unattached garage or shop with plumbing facilities.
C. The minimum inside
diameter of a sewer service lateral shall be four inches and shall be equal to
or greater than the building sewer diameter. Service laterals in general shall
be placed at ninety degrees to the main sewer line to avoid excessive exposure
to other utilities during excavation for construction or maintenance of the
service lines. Angles other than ninety degrees may be approved for special
conditions such as cul-de-sac lots. In no case shall the angle between the main
and the service be less than ninety degrees. Service line connections shall not
be made at manholes except at cul-de-sacs.
D. The minimum slope of sewer
service lines shall be two percent (one-fourth inch per foot) except that for
unusual conditions, a slope of one percent (one-eighth inch per foot) may be
approved. It will be necessary, however, for the designer to provide a complete
analysis of the need for any sewer service lateral slope less than two percent.
The maximum slope shall be one hundred percent (forty-five degrees or one foot
per foot). Deep connection risers (see the standard detail for service lateral
to deep sewers) or drop connections to manholes must be used where service line
slopes would exceed one hundred percent.
E. Tees for service laterals shall
be installed at one hundred percent slope, and one-sixteenth or one-eighth bends
shall be installed to provide proper grade for service lateral. Service laterals
shall be extended to the end at street right-of-way line or easement line, when
a sewer is installed in easement. A water tight plug shall be installed in end
of lateral and a two inches by four inches wood marker shall be placed at
lateral end from pipe invert to two feet above the ground. Two inches by four
inches top to be painted white and marked with the depth of the lateral measured
from ground to invert of pipe. (Ord. 571 § 1 Exh. A (part), 2005)
16.04.050 Connection to existing sewers.
A. Connections to, and extensions of, existing sewers will occur to
facilitate new development.
B. Connections to existing manholes shall be
made with the following guidelines:
1. Where the invert of the connecting
pipe is two feet or less above the manhole shelf, a beaver slide will be
constructed utilizing Portland cement concrete. The sewage entering the manhole
will follow a smooth concrete channel transitioning evenly from the invert of
the inlet pipe into the main channel. Sewage will not be allowed to fall freely
to the manhole base.
2. Where the invert of the connecting pipe is more than
two feet above the manhole shelf, the contractor will be required to construct
an inside drop with the inlet pipe invert being located at the manhole shelf.
The sewage entering the manhole will follow a smooth concrete channel transition
from the inlet pipe into the main channel.
3. Where the invert is required
to enter below the shelf of the manhole, the inlet pipe will not enter below a
point where the crown of the new inlet pipe is below the crown of the outlet
pipe. The base of the manhole will be rebuilt if damaged in this process. The
sewage will enter the main flow in a smooth channel transitioning from the inlet
pipe to the main channel.
4. No pipe will enter an existing manhole where
the angle between the incoming flow and the outgoing flow is greater than ninety
degrees.
C. When sewers are extended from cleanouts, the entire cleanout
assembly, including the wye, shall be removed.
D. New building service
laterals will be made at existing tees where possible.
E. When tees do not
exist on the public sanitary sewer system, the new lateral sewer will enter the
collection system through a “cored opening with an approved
connector.” (Ord. 571 § 1 Exh. A (part), 2005)
16.04.060 Private sewer lines.
Private sewer systems shall be constructed in accordance with the UPC.
(Ord. 571 § 1 Exh. A (part), 2005)
16.04.070 System testing.
All pipes shall be pressure tested and manhole leaks tested per the latest
edition of the APWA Standard Specifications for Public Works Construction,
Oregon Chapter. (Ord. 571 § 1 Exh. A (part), 2005)
16.04.080 Sewage pump station design standards (Reserved).
(Ord. 571 § 1 Exh. A (part), 2005)
16.04.081 General.
A. The pump station shall be a ground level self-priming pump type
facility.
B. An engineer registered in the state of Oregon and experienced
in the design of such facilities shall design the station. Service area peak
flows, pump station cycle and hydrogen sulfide calculations shall be submitted
to the city for review and approval. (Ord. 571 § 1 Exh. A (part),
2005)
16.04.082 Construction.
Station construction will include: wet well, pump enclosure, associated
piping and valves, electrical controls, automatic dialer, visual alarm,
emergency power transfer switch and connection receptacle, lighting, heater,
ventilating fan, instrumentation, access road, fencing, landscaping, potable
water supply, and shall conform to the Department of Environmental Quality (DEQ)
standards and Oregon Administrative Rules (OAR) Chapter 340, division 52. The
standard type pump station shall be equal to Hydro nix package pump stations.
(Ord. 571 § 1 Exh. A (part), 2005)
16.04.083 Capacities.
Pump station shall be designed to pump the peak wastewater flow from the
service area. When the service area is not built out, staging of pump station
capacity will be allowed. The wet well shall be sized to allow for a minimum
number of starts per hour. Inlet piping will not be used as a portion of the wet
well. (Ord. 571 § 1 Exh. A (part), 2005)
16.04.084 Hydrogen sulfide.
Calculations for hydrogen sulfide production shall be performed. Hydrogen
sulfide control equipment shall be installed as required. The method used (flow
back, air injection, chemical injection) shall be reviewed and approved by the
public works director. (Ord. 571 § 1 Exh. A (part), 2005)
16.04.085 Electrical.
A. Electrical. Pump station and related facilities will be constructed to
electrical and building codes.
Electrical controls shall be located above
ground mounted in a waterproof enclosure. Electrical panels shall be listed. The
pump station wet well shall be considered a hazardous location. Level controls
in the wet well shall be intrinsically safe.
B. Controls. Controls may be
mechanical relays or programmable logic controllers. Pumps shall automatically
alternate lead-lag position with each pumping cycle.
Pump level control
shall be by multitrode.
C. Power. An auxiliary power generator shall be
provided with a manual transfer switch mounted in the interior.
Alarms
include: pump failure, power failure, telemetry failure, high water level and
generator failure. (Ord. 571 § 1 Exh. A (part), 2005)
16.04.086 Materials.
A. Pumps. A minimum of two pumps shall be supplied. Each pump shall be
capable of pumping the peak wastewater flow. Where more than two pumps are used,
the station shall be able to pump peak wastewater flow when the largest pump is
out of service.
Pumps shall be self-priming pumps, with V-belt drives,
manufactured by Hydromatic, Gorman Rupp or equal, explosion proof suitable for
hazardous location when required, and shall be UL or FM listed.
B. Piping
and Valves. Piping and fittings shall be ductile iron to a point at least two
feet outside the station. Valves shall be metal, suitable for wastewater use.
Valves shall be designed for wastewater service. Provide pressure gauges with
isolation and purge valves on pump suction and discharge piping.
Steel
fabrications shall be hot dipped galvanized. Painting is required on valves,
piping and pipe fittings.
Force main shall be designed for nominal flow
velocity in the range of three to five foot per section.
Force mains shall
not be less than four inches in diameter for raw sewage.
C. Spare Parts.
Supply two sets each of all gaskets, bearings, V-belts, and mechanical seals for
rotation equipment. (Ord. 571 § 1 Exh. A (part), 2005)
16.04.087 Additional features.
A. Provide one inch antifreeze hose bib. Potable water shall be provided
by an above ground reduced pressure backflow preventer.
B. Provide positive
ventilation in the enclosure.
C. Provide odor control as
required.
D. Landscaping will only be required when the station is visible
from the public roadway and then only to blend with the local
aesthetics.
E. A six-foot chain link fence shall surround the pump station
when required by the public works director. (Ord. 571 § 1 Exh. A (part),
2005)
16.04.088 Operating and maintenance data.
A. Compile product data and related information appropriate for
city’s maintenance and operation or products furnished under the
contract.
B. Prepare operations and maintenance manual.
C. Instruct
city’s personnel in the maintenance of products and in the operation of
equipment and systems. (Ord. 571 § 1 Exh. A (part), 2005)
16.04.090 Erosion control.
A. Erosion control will be required for all areas disturbed during
construction and following construction until permanent protection is
established.
B. Temporary facilities may include silt fences, drain
barriers, gravel entries, ditches, surface stabilization or other devices as
necessary.
C. Temporary/permanent hydroseeding or acceptable seeding and
mulching must be provided whenever perennial cover cannot be established on
sites, which will be exposed after September 1 or prior to June 1. (Ord. 571
§ 1 Exh. A (part), 2005)
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