23-105227-CSWPPP-10.27.23.pdfSECTION C.3 CONSTRUCTION STORMWATER POLLUTION PREVENTION (CSWPP) MEASURES
The above measures must be implemented as needed to prevent the discharge of sediment-laden water and
other pollutants from the construction site. Proposed measures must be shown on the Simplified site
CSWPP plan required to be submitted with the Simplified drainage plans. Site-specific conditions during
construction may require additional measures as deemed necessary by DPER. As noted in Section C.3
above, other ESC and/or SWPPS measures found in Appendix D of the SWDM may be needed or may be
more appropriate for the project site as determined by DPER.
C.3.1 STABILIZED CONSTRUCTION ENTRANCE
Purpose
Construction entrances are stabilized to reduce the amount of sediment transported onto paved roads by
motor vehicles or runoff by constructing a stabilized pad of quarry spalls at the entrances to construction
sites.
Application
Construction entrances shall be stabilized wherever traffic will be leaving a construction site and traveling
on paved roads or other paved areas within 1,000 feet of the site.
Design and Installation Specifications
1. See Figure C.3.1.A for details.
2. A separation geotextile shall be placed under the spalls to prevent fine sediment from pumping up into
the rock pad. The geotextile shall meet the following standards:
Grab Tensile Strength (ASTM D4632) 200 lbs min.
Grab Tensile Elongation (ASTM D4632) 30% max.(woven)
Puncture Strength (ASTM D6241) 495 lbs min.
AOS (ASTM D4751) 20-45 (U.S. standard sieve size)
3. Hog fuel (wood based mulch) may be substituted for or combined with quarry spalls in areas that will
not be used for permanent roads. The effectiveness of hog fuel is highly variable, but it has been used
successfully on many construction sites. It generally requires more maintenance than quarry spalls.
Hog fuel is not recommended for entrance stabilization in urban areas. The inspector may at any time
require the use of quarry spalls if the hog fuel is not preventing sediment from being tracked onto
pavement or if the hog fuel is being carried onto pavement. Hog fuel is prohibited in permanent
roadbeds because organics in the subgrade soils cause difficulties with compaction.
4. Whenever possible, the entrance shall be constructed on a firm, compacted subgrade. This can
substantially increase the effectiveness of the pad and reduce the need for maintenance.
Maintenance
1. Quarry spalls (or hog fuel) shall be added if the pad is no longer in accordance with the specifications.
2. If the entrance is not preventing sediment from being tracked onto pavement, then alternative measures
to keep the streets free of sediment shall be used. This may include street sweeping, an increase in the
dimensions of the entrance, or the installation of a wheel wash. If washing is used, it shall be done on
an area covered with crushed rock, and wash water shall drain to a sediment trap or pond.
3. Any sediment that is tracked onto pavement shall be removed immediately by sweeping. The
sediment collected by sweeping shall be removed or stabilized onsite. The pavement shall not be
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C.3.1 STABILIZED CONSTRUCTION ENTRANCE
cleaned by washing down the street, except when sweeping is ineffective and there is a threat to public
safety. If it is necessary to wash the streets, a small sump must be constructed. The sediment would
then be washed into the sump where it can be controlled. Wash water must be pumped back onto the
site and cannot discharge to systems tributary to surface waters.
4. Any quarry spalls that are loosened from the pad and end up on the roadway shall be removed
immediately.
FIGURE C.3.1.A STABILIZED CONSTRUCTION ENTRANCE
PER KING COUNTY ROAD DESIGN AND CONSTRUCTION STANDARDS (KCRDCS), DRIVEWAYS SHALL
BE PAVED TO EDGE OF R-O-W PRIOR TO INSTALLATION OF THE CONSTRUCTION ENTRANCE TO
AVOID DAMAGING OF THE ROADWAY.
IT IS RECOMMENDED THAT THE ENTRANCE BE CROWNED SO THAT RUNOFF DRAINS OFF THE PAD.
PROVIDE FULL WIDTH OF
INGRESS/EGRESS AREA
IF A ROADSIDE DITCH IS
PRESENT, INSTALL
DRIVEWAY CULVERT
PER KCRDCS
GEOTEXTILE
4"- 8" QUARRY
SPALLS
R=25' MIN.
NOTES:
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C-109
SECTION C.3 CONSTRUCTION STORMWATER POLLUTION PREVENTION (CSWPP) MEASURES
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C.3.6 SILT FENCE
Purpose
Use of a silt fence reduces the transport of coarse sediment from a construction site by providing a
temporary physical barrier to sediment and reducing the runoff velocities of overland flow.
Conditions of Use
Silt fence may be used downslope of all disturbed areas. Silt fence is not intended to treat concentrated
flows, nor is it intended to treat substantial amounts of overland flow.
Design and Installation Specifications
1. See Figure C.3.6.A and Figure C.3.6.B for details.
2. The geotextile used must meet the standards listed below. A copy of the manufacturer's fabric
specifications must be available onsite.
AOS (ASTM D4751) 30-100 sieve size (0.60-0.15 mm) for slit film
50-100 sieve size (0.30-0.15 mm) for other fabrics
Water Permittivity (ASTM D4491) 0.02 sec-1 minimum
Grab Tensile Strength (ASTM D4632)
(see Specification Note 3)
180 lbs. min. for extra strength fabric
100 lbs. min. for standard strength fabric
Grab Tensile Elongation (ASTM D4632) 30% max. (woven)
Ultraviolet Resistance (ASTM D4355) 70% min.
3. Standard strength fabric requires wire backing to increase the strength of the fence. Wire backing or
closer post spacing may be required for extra strength fabric if field performance warrants a stronger
fence.
4. Where the fence is installed, the slope shall be no steeper than 2H:1V.
5. If a typical silt fence (per Figure C.3.6.A) is used, the standard 4 x 4 trench may not be reduced as
long as the bottom 8 inches of the silt fence is well buried and secured in a trench that stabilizes the
fence and does not allow water to bypass or undermine the silt fence.
6. Silt fences shall be located so as to avoid interfering with the movement of juvenile salmonids
attempting to enter off-channel areas or drainages.
Maintenance Standards
1. Any damage shall be repaired immediately.
2. If concentrated flows are evident uphill of the fence, they must be intercepted and conveyed to a
sediment trap or pond.
3. It is important to check the uphill side of the fence for signs of the fence clogging and acting as a
barrier to flow and then causing channelization of flows parallel to the fence. If this occurs, replace
the fence or remove the trapped sediment.
4. Sediment must be removed when the sediment is 6 inches high.
5. If the filter fabric (geotextile) has deteriorated due to ultraviolet breakdown, it shall be replaced.
C.3.6 SILT FENCE
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FIGURE C.3.6.A SILT FENCE
FIGURE C.3.6.B SILT FENCE INSTALLATION AND MAINTENANCE
2"X2" BY 14 Ga. WIRE OR
EQUIVALENT, IF STANDARD
STRENGTH FABRIC USED
NOTE: FILTER FABRIC FENCES
SHALL BE INSTALLED ALONG
CONTOURS WHENEVER POSSIBLE
JOINTS IN FILTER FABRIC SHALL BE SPLICED
AT POSTS. USE STAPLES, WIRE RINGS OR
EQUIVALENT TO ATTACH FABRIC TO POSTS.
FILTER FABRIC
BACKFILL TRENCH WITH NATIVE SOIL
OR 3/4" TO 1-1/2" WASHED GRAVEL
MINIMUM 4"x4" TRENCH
2"x4" WOOD POSTS, STEEL FENCE
POSTS, REBAR, OR EQUIVALENT
POST SPACING MAY BE
INCREASED TO 8' IF
WIRE BACKING IS USED
6' MAX.
SECTION C.3 CONSTRUCTION STORMWATER POLLUTION PREVENTION (CSWPP) MEASURES
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C.3.9 STORM DRAIN INLET PROTECTION
Purpose
Storm drain inlets are protected to prevent coarse sediment from entering storm drainage systems.
Temporary devices around storm drains assist in improving the quality of water discharged to inlets or
catch basins by ponding sediment-laden water. These devices are effective only for relatively small
drainage areas.
Conditions of Use
1. Protection shall be provided for all storm drain inlets downslope and within 500 feet of a disturbed or
construction area, unless the runoff that enters the catch basin will be conveyed to a sediment pond or
trap.
2. Inlet protection may be used anywhere at the applicant's discretion to protect the drainage system.
This will, however, require more maintenance, and it is highly likely that the drainage system will still
require some cleaning.
3. The contributing drainage area must not be larger than one acre.
Design and Installation Specifications
1. There are many options for protecting storm drain inlets. Two commonly used options are filter
fabric protection and catch basin inserts. Filter fabric protection (see Figure C.3.9.A) is filter fabric
(geotextile) placed over the grate. This method is generally very ineffective and requires intense
maintenance efforts. Catch basin inserts (see Figure C.3.9.B) are manufactured devices that nest
inside a catch basin. This method also requires a high frequency of maintenance to be effective. Both
options provide adequate protection, but filter fabric is likely to result in ponding of water above the
catch basin, while the insert will not. Thus, filter fabric is only allowed where ponding will not be a
traffic concern and where slope erosion will not result if the curb is overtopped by ponded water.
Trapping sediment in the catch basins is unlikely to improve the water quality of runoff if it is treated
in a pond or trap because the coarse particles that are trapped at the catch basin settle out very quickly
in the pond or trap. Catch basin protection normally only improves water quality where there is
no treatment facility downstream . In these circumstances, catch basin protection is an important
last line of defense. It is not, however, a substitute for preventing erosion.
The placement of filter fabric under grates is generally prohibited and the use of filter fabric over
grates is strictly limited and discouraged.
2. It is sometimes possible to construct a small sump around the catch basin before final surfacing of the
road. This is allowed because it can be a very effective method of sediment control.
3. Block and gravel filters, gravel and wire mesh filter barriers, and bag barriers filled with various
filtering media placed around catch basins can be effective when the drainage area is 1 acre or less and
flows do not exceed 0.5 cfs. It is necessary to allow for overtopping to prevent flooding. Many
manufacturers have various inlet protection filters that are very effective in keeping sediment-laden
water from entering the storm drainage system. The following are examples of a few common
methods.
a) Block and gravel filters (Figure C.3.9.C) are a barrier formed around an inlet with standard
concrete block and gravel, installed as follows:
Height is 1 to 2 feet above the inlet.
Recess the first row of blocks 2 inches into the ground for stability.
Support subsequent rows by placing a 2x4 through the concrete block opening.
C.3.9 STORM DRAIN INLET PROTECTION
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Do not use mortar.
Lay some blocks in the bottom row on their side for dewatering the pooled water.
Place cloth or mesh with ½ inch openings over all block openings.
Place gravel below the top of blocks on slopes of 2:1 or flatter.
An alternate design is a gravel donut.
b) Gravel and wire mesh filters consist of a gravel barrier placed over the top of an inlet. This
structure generally does not provide overflow. Install as follows:
Cloth or comparable wire mesh with ½ inch openings is placed over inlet.
Coarse aggregate covers the cloth or mesh.
Height/depth of gravel should be 1 foot or more, 18 inches wider than inlet on all sides.
c) Curb inlet protection with a wooden weir is a barrier formed around an inlet with a wooden
frame and gravel, installed as follows:
Construct a frame and attach wire mesh (½ inch openings) and filter fabric to the frame.
Pile coarse washed aggregate against the wire/fabric.
Place weight on frame anchors.
d) Curb and gutter sediment barriers (Figure C.3.9.D) consist of sandbags or rock berms (riprap
and aggregate) 3 feet high and 3 feet wide in a horseshoe shape, installed as follows:
Bags of either burlap or woven geotextile fabric, filled with a variety of media such as gravel,
wood chips, compost or sand stacked tightly allows water to pond and allows sediment to
separate from runoff.
Leave a "one bag gap" in the top row of the barrier to provide a spillway for overflow.
Construct a horseshoe shaped berm, faced with coarse aggregate if using riprap, 3 x 3 and at
least 2 feet from the inlet.
Construct a horseshoe shaped sedimentation trap on the outside of the berm to sediment trap
standards for protecting a culvert inlet.
4. Excavated drop inlet sediment traps are appropriate where relatively heavy flows are expected and
overflow capability is needed. If emergency overflow is provided, additional end-of-pipe treatment
may be required. Excavated drop inlets consist of an excavated impoundment area around a storm
drain. Sediment settles out of the stormwater prior to enter the drain. Install according to the following
specifications:
a) The impoundment area should have a depth of 1 - 2 feet measured from the crest of the inlet
structure.
b) Side slopes of the excavated area must be no steeper than 2:1.
c) Minimum volume of the excavated area should be 35 cubic yards.
d) Install provisions for draining the area to prevent standing water problems.
e) Keep the area clear of debris.
f) Weep holes may be drilled into the side of the inlet.
g) Protect weep holes with wire mesh and washed aggregate.
h) Weep holes must be sealed when removing and stabilizing excavated area.
i) A temporary dike may be necessary on the down slope side of the structure to prevent bypass
flow.
SECTION C.3 CONSTRUCTION STORMWATER POLLUTION PREVENTION (CSWPP) MEASURES
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Maintenance Standards
1. Any accumulated sediment on or around inlet protection shall be removed immediately. Sediment
shall not be removed with water, and all sediment must be disposed of as fill on site or hauled off site.
2. Any sediment in the catch basin insert shall be removed when the sediment has filled one-third of the
available storage. The filter media for the insert shall be cleaned or replaced at least monthly.
3. Regular maintenance is critical for all forms of catch basin/inlet protection. Unlike many forms of
protection that fail gradually, catch basin protection will fail suddenly and completely if not
maintained properly.
FIGURE C.3.9.A FILTER FABRIC PROTECTION
FIGURE C.3.9.B CATCH BASIN INSERT
NOTE: THIS DETAIL IS ONLY
SCHEMATIC. ANY INSERT IS
ALLOWED THAT HAS:
A MIN. 0.5 C.F. OF STORAGE,
THE MEANS TO DEWATER THE
STORED SEDIMENT,
AN OVERFLOW, AND
CAN BE EASILY MAINTAINED.
OVERFLOW
GRATECATCH BASIN
POROUS
BOTTOM
SOLID
WALLS
FILTER
MEDIA FOR
DEWATERING
CATCH BASIN
NOTE: ONLY TO BE USED WHERE
PONDING OF WATER ABOVE THE
CATCH BASIN WILL NOT CAUSE
TRAFFIC PROBLEMS AND WHERE
OVERFLOW WILL NOT RESULT IN
EROSION OF SLOPES.
GRATE
STANDARD STRENGTH
FILTER FABRIC
C.3.9 STORM DRAIN INLET PROTECTION
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FIGURE C.3.9.C BLOCK AND GRAVEL CURB INLET PROTECTION
1. USE BLOCK AND GRAVEL TYPE SEDIMENT BARRIER WHEN CURB INLET IS LOCATED
IN GENTLY SLOPING SEGMENT, WHERE WATER CAN POND AND ALLOW SEDIMENT TO
SEPARATE FROM RUNOFF.
2. BARRIER SHALL ALLOW FOR OVERFLOW FROM SEVERE STORM EVENT.
3. INSPECT BARRIERS AND REMOVE SEDIMENT AFTER EACH STORM EVENT. SEDIMENT
AND GRAVEL MUST BE REMOVED FROM THE TRAVELED WAY IMMEDIATELY.
2x4 WOOD STUD
OVERFLOW
WATER
A
A
PLAN VIEW
NTS
SECTION A-A
NTS
BLOCK AND GRAVEL CURB INLET PROTECTION
NTS
CATCH BASIN COVER
CURB INLET
CONCRETE BLOCKS
CATCH BASIN COVER
CURB INLET
CATCH BASIN
BACK OF SIDEWALK
CURB FACE
3/4" DRAIN
GRAVEL (20 mm)
WIRE SCREEN OR
FILTER FABRIC
POND HEIGHT
WIRE SCREEN
OR FILTER FABRIC
2x4 WOOD STUD
(100x50 TIMBER STUD)
3/4" DRAIN
GRAVEL (20 mm)
NOTES:
SECTION C.3 CONSTRUCTION STORMWATER POLLUTION PREVENTION (CSWPP) MEASURES
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FIGURE C.3.9.D CURB AND GUTTER BARRIER PROTECTION
SECTION D.2.2 SWPPS MEASURES
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D.2.2.4 MATERIAL DELIVERY, STORAGE AND CONTAINMENT
Purpose
Prevent, reduce, or eliminate the discharge of pollutants to the stormwater system or watercourses from
material delivery and storage. Minimize the storage of hazardous materials on-site, store materials in a
designated area, and install secondary containment.
Conditions of Use
These procedures are suitable for use at all construction sites with delivery and storage of the following
materials:
Petroleum products such as fuel, oil and grease
Soil stabilizers and binders (e.g. Polyacrylamide)
Fertilizers, pesticides and herbicides
Detergents
Asphalt and concrete compounds
Hazardous chemicals such as acids, lime, adhesives, paints, solvents and curing compounds
Any other material that may be detrimental if released to the environment
Design and Installation Specifications
The following steps should be taken to minimize risk:
1. Temporary storage area should be located away from vehicular traffic, near the construction
entrance(s), and away from waterways or storm drains.
2. Material Safety Data Sheets (MSDS) should be supplied for all materials stored. Chemicals should be
kept in their original labeled containers.
3. Hazardous material storage on-site should be minimized.
4. Hazardous materials should be handled as infrequently as possible.
5. During the wet weather season (Oct 1 April 30), consider storing materials in a covered area.
6. Materials should be stored in secondary containments, such as earthen dike, horse trough, or even a
-reactive materials such as detergents, oil, grease, and paints. Small
7. Do not store chemicals, drums, or bagged materials directly on the ground. Place these items on a
pallet and, when possible, and within secondary containment.
8. If drums must be kept uncovered, store them at a slight angle to reduce ponding of rainwater on the
lids to reduce corrosion. Domed plastic covers are inexpensive and snap to the top of drums,
preventing water from collecting.
Material Storage Areas and Secondary Containment Practices:
1. Liquids, petroleum products, and substances listed in 40 CFR Parts 110, 117, or 302 shall be stored in
approved containers and drums and shall not be overfilled. Containers and drums shall be stored in
temporary secondary containment facilities.
2. Temporary secondary containment facilities shall provide for a spill containment volume able to
contain 10% of the total enclosed container volume of all containers, or 110% of the capacity of the
largest container within its boundary, whichever is greater.
D.2.2.4 MATERIAL DELIVERY, STORAGE AND CONTAINMENT
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3. Secondary containment facilities shall be impervious to the materials stored therein for a minimum
contact time of 72 hours.
4. Secondary containment facilities shall be maintained free of accumulated rainwater and spills. In the
event of spills or leaks, accumulated rainwater and spills shall be collected and placed into drums.
These liquids shall be handled as hazardous waste unless testing determines them to be non-
hazardous.
5. Sufficient separation should be provided between stored containers to allow for spill cleanup and
emergency response access.
6. During the wet weather season (Oct 1 April 30), each secondary containment facility shall be
covered during non-working days, prior to and during rain events.
7. Keep material storage areas clean, organized and equipped with an ample supply of appropriate spill
clean-up material (spill kit).
8. The spill kit should include, at a minimum:
1-Water Resistant Nylon Bag
3-Oil Absorbent S
2-
12-
1-Pair Splash Resistant Goggles
3-Pair Nitrile Gloves
10-Disposable Bags with Ties
Instructions
D.2.2.3 SAWCUTTING AND SURFACING POLLUTION PREVENTION
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D.2.2.3 SAWCUTTING AND SURFACING POLLUTION PREVENTION
Purpose
Sawcutting and surfacing operations generate slurry and process water that contains fine particles and high
pH (concrete cutting), both of which can violate the water quality standards in the receiving water.
Concrete spillage or concrete discharge to surface waters of the State is prohibited. Use this BMP to
minimize and eliminate process water and slurry created through sawcutting or surfacing from entering
waters of the State.
Conditions of Use
Utilize these management practices anytime sawcutting or surfacing operations take place. Sawcutting and
surfacing operations include, but are not limited to, sawing, coring, grinding, roughening, hydro-
demolition, bridge and road surfacing
Design and Installation Specifications
1. Vacuum slurry and cuttings during cutting and surfacing operations.
2. Slurry and cuttings shall not remain on permanent concrete or asphalt pavement overnight.
3. Slurry and cuttings shall not drain to any natural or constructed drainage conveyance including
stormwater systems. This may require temporarily blocking catch basins.
4. Dispose of collected slurry and cuttings in a manner that does not violate ground water or surface
water quality standards.
5. Do not allow process water generated during hydro-demolition, surface roughening or similar
operations to drain to any natural or constructed drainage conveyance including stormwater systems.
Dispose process water in a manner that does not violate ground water or surface water quality
standards.
6. Handle and dispose cleaning waste material and demolition debris in a manner that does not cause
contamination of water. Dispose of sweeping material from a pick-up sweeper at an appropriate
disposal site.
Maintenance Standards
Continually monitor operations to determine whether slurry, cuttings, or process water could enter waters
of the state. If inspections show that a violation of water quality standards could occur, stop operations and
immediately implement preventive measures such as berms, barriers, secondary containment, and vacuum
trucks.
D.2.2.1 CONCRETE HANDLING
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D.2.2.1 CONCRETE HANDLING
Purpose
Concrete work can generate process water and slurry that contain fine particles and high pH, both of which
can violate water quality standards in the receiving water. Concrete spillage or concrete discharge to
surface waters of the State is prohibited. Use this BMP to minimize and eliminate concrete, concrete
process water, and concrete slurry from entering waters of the state.
Conditions of Use
Any time concrete is used, utilize these management practices. Concrete construction projects include, but
are not limited to, curbs, sidewalks, roads, bridges, foundations, floors, stormwater vaults, retaining walls,
driveways and runways.
Design and Installation Specifications
1. Assure that washout of concrete trucks, chutes, pumps, and internals is performed at an approved off-
site location or in designated concrete washout areas. Do not wash out concrete trucks, chutes, pumps,
or internals onto the ground, or into storm drains, open ditches, streets, or streams. Refer to BMP
D.2.2.2 (p. D-78) for information on concrete washout areas.
2. Return unused concrete remaining in the truck and pump to the originating batch plant for recycling.
Do not dump excess concrete on site, except in designated concrete washout areas.
3. Wash off hand tools including, but not limited to, screeds, shovels, rakes, floats, and trowels into
formed areas awaiting future concrete pours only.
4. Do not wash out to formed areas awaiting infiltration BMPs.
5. Wash equipment difficult to move, such as concrete pavers in areas that do not directly drain to
natural or constructed stormwater conveyances.
6. Do not allow washdown from areas, such as concrete aggregate driveways, to drain directly to natural
or constructed stormwater conveyances.
7. Contain washwater and leftover product in a lined container when no formed areas are available,.
Dispose of contained concrete in a manner that does not violate ground water or surface water quality
standards.
8. Always use forms or solid barriers for concrete pours, such as pilings, within 15-feet of surface
waters.
9. Refer to BMPs D.2.2.7 and D.2.2.8 for pH adjustment requirements.
10. Refer to the Construction Stormwater General Permit for pH monitoring requirements if the project
involves one of the following activities:
Significant concrete work (greater than 1,000 cubic yards poured concrete or recycled concrete
used over the life of a project).
The use of engineered soils amended with (but not limited to) Portland cement-treated base,
cement kiln dust or fly ash.
Discharging stormwater to segments of water bodies on the 303(d) list (Category 5) for high pH.
Maintenance Standards
Check containers for holes in the liner daily during concrete pours and repair the same day.
SECTION D.2.1 ESC MEASURES
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D.2.1.8 DUST CONTROL
Preventative measures to minimize the wind transport of soil shall be taken when a traffic hazard may be
created or when sediment transported by wind is likely to be deposited in water resources or adjacent
properties.
Purpose: To prevent wind transport of dust from exposed soil surfaces onto roadways, drainage ways, and
surface waters.
When to Install: Dust control shall be implemented when exposed soils are dry to the point that wind
transport is possible and roadways, drainage ways, or surface waters are likely to be impacted. Dust
control measures may consist of chemical, structural, or mechanical methods.
Measures to Install: Water is the most common dust control (or palliative) used in the area. When using
water for dust control, the exposed soils shall be sprayed until wet, but runoff shall not be generated by
spraying. Calcium chloride, Magnesium chloride, Lignin derivatives, Tree Resin Emulsions, and
Synthetic Polymer Emulsions may also be used for dust control. Exposed areas shall be re-sprayed as
needed. Oil shall not be used for dust control. The following table lists many common dust control
measures. Some of the measures are not recommended for use in King County and must have prior
approval prior to use from the DLS-Permitting inspector assigned to specific projects.
D.2.1.8 DUST CONTROL
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TABLE D.2.1.8.A DUST CONTROL MEASURES
METHOD CONSIDERATIONS SITE PREPARATION RECOMMENDED
APPLICATION RATE
Water -Most commonly used practice
-Evaporates quickly
-Lasts less than 1 day
For all liquid agents:
-Blade a small surface
-Crown or slope surface to avoid
ponding
-Compact soils if needed
-Uniformly pre-wet at
0.03 0.3 gal/sq yd
-Apply solution under pressure.
Overlap solution 6 12 inches
-Allow treated area to cure
0 4 hours
-Compact area after curing
-Apply second treatment before first
treatment becomes ineffective
0.125 gal/sq yd every
20 to 30 minutes
Salts
Calcium
Chloride
(CaCl)
-Restricts evaporation
-Lasts 6-12 months
-Can be corrosive
-Less effective in low humidity
-Can build up in soils and leach by rain
Apply 38% solution at
1.21L/m2 (0.27 gal/yd2)
or as loose dry granules
per manufacturer
Magnesium
Chloride
(MgCl)
-Restricts evaporation
-Works at higher temperatures and lower
humidity than CaCl
-May be more costly than CaCl
Apply 26 32% solution
at 2.3 L/m2 (0.5
gal/yd2)
Sodium
Chloride
(NaCl)
-Effective over smaller range of
conditions
-Less expensive
-Can be corrosive
-Less effective in low humidity
Per Manufacturer
Silicates -Generally expensive
-Available in small quantities
-Require Second application
Surfactants -High evaporation rates
-Effective for short time periods
-Must apply frequently
Copolymers -Forms semi-permeable transparent
crust
-Resists ultraviolet radiation and
moisture induced breakdown
-Last 1 to 2 years
750 940 L/ha (80
100 gal/ac)
Petroleum
Products
-Used oil is prohibited as a dust control
method
-Bind soil particles
-May hinder foliage growth
-Environmental and aesthetic concerns
-Higher cost
Use 57 63% resins as
base. Apply at 750
940 L/ha (80-100
gal/ac)
Lignin
Sulfonate
-Paper industry waste product
-Acts as dispersing agent
-Best in dry climates
-Can be slippery
-Will decrease Dissolved Oxygen in
waterways therefore cannot be used
adjacent to surface water systems
Loosen surface 25-50
mm (1 2 inches) Need
4-8% fines
Vegetable
Oils
-Coat grains of soils, so limited binding
ability
-May become brittle
-Limited availability
Per Manufacturer
Spray on
Adhesives
-Available as organic or synthetic
-Effective on dry, hard soils
-Forms a crust
-Can last 3 to 4 years
Per Manufacturer
SECTION C.3 CONSTRUCTION STORMWATER POLLUTION PREVENTION (CSWPP) MEASURES
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C.3.4 PLASTIC COVERING
Purpose
Plastic covering provides immediate, short-term erosion protection to slopes and disturbed areas.
Conditions of Use
1. Plastic covering may be used on disturbed areas that require cover measures for less than 30 days.
2. Plastic is particularly useful for protecting cut and fill slopes and stockpiles. Note: The relatively
rapid breakdown of most polyethylene sheeting makes it unsuitable for long-term applications.
3. Clear plastic sheeting may be used over newly-seeded areas to create a greenhouse effect and
encourage grass growth. Clear plastic should not be used for this purpose during the summer months
because the resulting high temperatures can kill the grass.
4. Due to rapid runoff caused by plastic sheeting, this method shall not be used upslope of areas that
might be adversely impacted by concentrated runoff. Such areas include steep and/or unstable slopes.
Note: There have been many problems with plastic, usually attributable to poor installation and
maintenance. However, the material itself can cause problems, even when correctly installed and
maintained, because it generates high-velocity runoff and breaks down quickly due to ultraviolet
radiation. In addition, if the plastic is not completely removed, it can clog drainage system inlets and
outlets. It is highly recommended that alternatives to plastic sheeting be used whenever possible and that
its use be limited.
Design and Installation Specifications
1. See Figure C.3.4.A for details.
2. Plastic sheeting shall have a minimum thickness of 0.06 millimeters.
3. If erosion at the toe of a slope is likely, a gravel berm, riprap, or other suitable protection shall be
installed at the toe of the slope in order to reduce the velocity of runoff.
FIGURE C.3.4.A PLASTIC COVERING
TIRES, SANDBAGS, OR
EQUIVALENT MAY BE USED
TO WEIGHT PLASTIC
SEAMS BETWEEN SHEETS
MUST OVERLAP A MINIMUM
OF 12" AND BE WEIGHTED
OR TAPED
TOE IN SHEETING
IN MINIMUM 4"X4"
TRENCH
PROVIDE ENERGY DISSIPATION
AT TOE WHEN NEEDED
10' MAX.
10' MAX.
C.3.5 MARK CLEARING LIMITS/MINIMIZE CLEARING
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Maintenance Standards for Plastic Covering
1. Torn sheets must be replaced and open seams repaired.
2. If the plastic begins to deteriorate due to ultraviolet radiation, it must be completely removed and
replaced.
C.3.5 MARK CLEARING LIMITS/MINIMIZE CLEARING
Purpose
Minimizing clearing is the most effective method of erosion control. Undisturbed vegetation intercepts
and slows rainwater. Plant roots hold soil in place, and dead vegetation on the ground acts as a mulch.
Applications
Clearing limits shall be marked and clearing minimized on any site where significant areas of undisturbed
vegetation will be retained.
Design Specifications
1. Minimizing clearing should be incorporated into the site design. Clearing limits must be marked on
the Simplified site CSWPP plan.
2. On the ground, clearing limits must be clearly marked with brightly colored tape or plastic or metal
safety fencing. If tape is used, it should be supported by vegetation or stakes, and should be about 3 to
6 feet high and highly visible. Equipment operators should be informed of areas of vegetation that are
to be left undisturbed.
3. The duff layer, native top soil, and natural vegetation shall be retained in an undisturbed state to the
maximum extent practicable. If it is not practicable to retain the duff layer in place, it should be
stockpiled on-site, covered to prevent erosion, and replaced immediately upon completion of the
ground disturbing activities.
Maintenance
Fencing shall be inspected regularly and repaired or replaced as needed.
SECTION C.3 CONSTRUCTION STORMWATER POLLUTION PREVENTION (CSWPP) MEASURES
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C.3.2 MULCHING
Purpose
The purpose of mulching soils is to provide immediate temporary protection from erosion. Mulch also
enhances plant establishment by conserving moisture, holding fertilizer, seed, and topsoil in place, and
moderating soil temperatures. There is an enormous variety of mulches that may be used. Only the most
common types are discussed in this section.
Conditions of Use
As a temporary cover measure, mulch should be used:
1. On disturbed areas that require cover measures for less than 30 days
2. As a cover for seed during the wet season and during the hot summer months
3. During the wet season on slopes steeper than 3H:1V with more than 10 feet of vertical relief.
Design and Installation Specifications
For mulch materials, application rates, and specifications, see Table C.3.2.A. Note: Thicknesses may be
increased for disturbed areas in or near critical areas or other areas highly susceptible to erosion.
Maintenance Standards
1. The thickness of the mulch cover must be maintained.
2. Any areas that experience erosion shall be re-mulched and/or protected with a net or blanket. If the
erosion problem is drainage related, then the drainage problem shall be assessed and alternate drainage
such as interceptor swales may be needed to fix the problem and the eroded area re-mulched.
C.3.2 MULCHING
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TABLE C.3.2.A MULCH STANDARDS AND GUIDELINES
Mulch
Material
Quality Standards Application
Rates
Remarks
Straw Air-dried; free from
undesirable seed and
coarse material
2"-3" thick; 2-3
bales per 1000 sf
or 2-3 tons per acre
Cost-effective protection when applied with adequate
thickness. Hand-application generally requires greater
thickness than blown straw. Straw should be crimped to
avoid wind blow. The thickness of straw may be reduced
by half when used in conjunction with seeding.
Wood Fiber
Cellulose
No growth inhibiting
factors
Approx. 25-30 lbs
per 1000 sf or
1000-1500 lbs per
acre
Shall be applied with hydromulcher. Shall not be used
without seed and tackifier unless the application rate is at
least doubled. Some wood fiber with very long fibers can
be effective at lower application rates and without seed
or tackifier.
Compost No visible water or dust
during handling. Must
be purchased from
supplier with Solid
Waste Handling Permit.
2" thick min.;
approx. 100 tons
per acre (approx.
800 lbs per cubic
yard)
More effective control can be obtained by increasing
thickness to 3". Excellent mulch for protecting final
grades until landscaping because it can be directly
seeded or tilled into soil as an amendment.
Hydraulic
Matrices
(Bonded Fiber
Matrix)
This mulch category
includes hydraulic
slurries composed of
wood fiber, paper fiber
or a combination of the
two held together by a
binding system. The
BFM shall be a mixture
of long wood fibers and
various bonding agents.
Apply at rates from
3,000 lbs per acre
to 4,000 lbs per
acre and based on
manufacturers
recommendations
The BFM shall not be applied immediately before, during
or immediately after rainfall so that the matrix will have
an opportunity to dry for 24 hours after installation.
Application rates beyond 2,500 pounds may interfere
with germination and are not usually recommended for
turf establishment. BFM is generally a matrix where all
fiber and binders are in one bag, rather than having to
mix components from various manufacturers to create a
matrix. BFMs can be installed via helicopter in remote
areas. They are approximately $1,000 per acre cheaper
to install.
Chipped Site
Vegetation
Average size shall be
several inches.
2" minimum
thickness
This is a cost-effective way to dispose of debris from
clearing and grubbing, and it eliminates the problems
associated with burning. Generally, it should not be used
on slopes above approx. 10% because of its tendency to
be transported by runoff. It is not recommended within
200 feet of surface waters. If seeding is expected shortly
after mulch, the decomposition of the chipped vegetation
may tie up nutrients important to grass establishment.