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40.380.050 Erosion Control
A. Small Parcel Development Requirements.
1. Construction Access. Construction vehicle access shall be limited, wherever possible, to only one (1) route. Access points shall be stabilized with two (2) to four (4) inch diameter gravel to minimize tracking of sediment (mud) onto public roads. Vehicles not performing a construction activity shall not be permitted off-street. Worker personal vehicles shall be parked on adjacent streets or other approved areas.
2. Stabilization of Denuded Areas. All exposed and unworked soils shall be stabilized by suitable application of BMPs, including but not limited to sod or other vegetation, plastic covering, mulching, or application of ground base on areas to be paved. All BMPs shall be selected, designed, and maintained in accordance with the BMP manual. From October 1st through April 30th, no soils shall remain exposed for more than two (2) days. From May 1st through September 30th, no soils shall remain exposed for more for seven (7) days. Construction materials such as lumber shall be delivered and stored on designated locations that are stabilized and protected from erosion. All sidewalk areas shall be pre-graded and stabilized for use as sediment traps.
3. Protection of Water Bodies and Adjacent Properties. Water bodies and adjacent properties shall be protected from sediment deposition by appropriate use of vegetative buffer strips, sediment barriers or filters, dikes, mulching, or by a combination of these measures and other appropriate BMPs. Each owner, builder, or permit holder shall install and maintain inlet protection on storm drain inlets impacted from construction activity on their site.
4. Maintenance. All erosion and sediment control BMPs shall be inspected and maintained and repaired as needed to ensure continued performance of their intended function. Maintenance and repair shall be conducted in accordance with the BMP manual or approved site plans. A maintenance log for private facilities shall be provided and kept as a permanent record. The maintenance log shall be in a designated on-site location. Uncompleted construction sites shall be inspected at least once a week and after each rainfall and shall be repaired if needed. An inspection log shall be maintained from the beginning of construction until the completion of the warranty period and final project inspection.
5. Sediment Removal from Roadways. If sediment is transported onto a road surface, the roads shall be cleaned thoroughly at the end of the work day, or more often if necessary. Significant soil deposits shall be removed from roads by shoveling or sweeping. Street washing, which must be approved by the responsible official, shall be allowed only after sediment is removed in this manner. Prior to washing, all inlets and down-stream facilities must be protected.
(Amended: Ord. 2004-06-11)
B. Large Parcel Development Requirements.
1. Construction Access Route. Construction vehicle access shall be limited to specific access points. Access points shall include a temporary sedimentation pond or other approved BMP to contain or treat wash water from construction vehicles. Use of more than one (1) access point shall require approval of the responsible official. Access points shall be stabilized with two (2) inch diameter gravel to minimize the tracking of sediment (mud) onto public roads. Evidence of tracking of material from a construction site may require construction activities to cease until corrections are made.
2. Sediment Removal from Roadways. If sediment is transported onto a road surface, the roads shall be cleaned thoroughly at the end of the work day, or more often if necessary. Significant soil deposits shall be removed from roads by shoveling or sweeping. Street washing, which must be approved by the responsible official, shall be allowed only after sediment is removed in this manner. Prior to washing, all inlets and downstream facilities must be protected.
3. Delineate Clearing and Easement Limits. At the site, mark clearing limits and/or any easements, setbacks, sensitive/critical areas and their buffers, trees and drainage courses.
4. Stabilization and Sediment Trapping. All exposed and unworked soils shall be stabilized by suitable application of BMPs. From October 1st to April 30th, no soils shall remain unstabilized for more than two (2) days. From May 1st to September 30th, no soils shall remain unstabilized for more than seven (7) days. Prior to leaving the site, stormwater runoff shall pass through a sediment pond or sediment trap, or other appropriate BMPs.
5. Protection of Water Bodies and Adjacent Properties. Water bodies and properties adjacent to the site shall be protected from sediment deposition by appropriate use of BMPs. Prior to leaving sites larger than one (1) acre, stormwater runoff shall pass through a sediment pond, sediment trap, or other appropriate BMP designed in accordance with the BMP manual. Sediment traps alone are not adequate on sites greater than three (3) acres. BMPs shall be selected, designed and maintained in accordance with the BMP manual.
6. Timing of Sediment Trapping Measures. Sediment ponds and traps, perimeter dikes, sediment barriers, and other BMPs intended to trap sediment on-site shall be constructed as a first step in grading. These BMPs shall be stabilized and functional before land-disturbing activities take place. Earthen structures such as dams, dikes, and diversions shall be seeded and mulched according to the timing indicated in Section 40.380.050(B)(4).
7. Infiltration System Protection. Permanent infiltration systems shall be isolated and protected from sedimentation by sediment traps, sacrificial systems, duplicate systems, or redundant systems.
8. Controlling Off-Site Erosion. Properties and waterways downstream from development sites shall be protected from erosion due to increases in the volume, velocity, and peak flow rate of stormwater runoff from the project site. Acceptable BMPs include temporary or permanent detention ponds and temporary infiltration BMPs limiting the discharge from a two (2) year storm to one-half (1/2) the pre-development two (2) year storm peak runoff rate.
9. Stabilization of Temporary Conveyance Channels and Outlets. All temporary on-site conveyance channels shall be designed, constructed and stabilized to prevent erosion from the expected velocity of flow from a two (2) year, twenty-four (24) hour frequency storm for the developed condition. Stabilization adequate to prevent erosion of outlets, adjacent streambanks, slopes and downstream reaches shall be provided at the outlets of all conveyance systems. BMPs shall be selected, designed and maintained in accordance with the BMP manual. Outlet protection shall also include energy dissipation structures or devices that retard peak flows to non-erosive conditions.
10. Storm Drain Inlet Protection. All storm drain inlets shall be protected so that stormwater runoff shall not enter the conveyance system without first being filtered or otherwise treated to remove sediment. BMPs shall be selected, designed and maintained in accordance with the BMP manual. Other BMPs may be utilized, provided they have prior approval by the responsible official.
11. Maintenance. All erosion and sediment control BMPs shall be inspected, maintained and repaired as needed to ensure continued performance of their intended function. Maintenance and repair shall be conducted in accordance with the BMP manual or approved site plan. A maintenance log for private facilities shall be provided and kept as a permanent record. The maintenance log shall be in a designated on-site location. Uncompleted construction sites shall be inspected at least once a week and after each rainfall and shall be repaired if needed. An inspection log shall be maintained from the beginning of construction until the completion of the warranty period and final project inspection.
12. Underground Utility Construction. The construction of underground utility lines shall be subject to the following criteria:
a. Where feasible, no more than five hundred (500) feet of trench shall be opened at one (1) time.
b. Excavated material shall be placed to minimize runoff into the trench and adjacent roadways consistent with safety and space considerations;
c. Trench dewatering devices shall discharge into a sediment trap or sediment pond;
d. BMPs shall be used to control erosion during and after construction;
e. BMPs damaged during construction shall be replaced or repaired; and
f. An erosion control plan specifically related to underground work shall be submitted and approved prior to beginning work.
13. Construction Site Dewatering. Dewatering devices shall discharge into a sediment trap or sediment pond.
14. Control of Pollutants Other Than Sediment on Construction Sites. All pollutants other than sediment that occur on-site during development shall be handled and disposed of in a manner that does not cause contamination of stormwater.
15. Removal of Temporary BMPs. All temporary erosion and sediment control BMPs shall be removed within thirty (30) days after final site stabilization is achieved or after the temporary BMPs are no longer needed. Trapped sediment shall be removed or stabilized on-site. Disturbed soil areas resulting from removal shall be permanently stabilized.
16. Cut and Fill Slopes. Cut and fill slopes shall be designed and constructed in a manner that will minimize erosion. In addition, slopes shall be stabilized in accordance with Section 40.380.050(B)(4).
17. If the BMPs approved and applied to a site are insufficient to prevent sediment from reaching water bodies, adjacent properties, or public rights-of-way, additional BMPs shall be implemented immediately by the property owner, person undertaking the activity, or permit holder.
(Amended: Ord. 2004-06-11)
C. Signage.
Erosion control signage approved by the responsible official shall be installed at each point of entry for any subdivision or short plat prior to issuance of provisional acceptance by the county. Signs may be purchased from the county. Removal of signage shall occur no sooner than the latter of: certificates of occupancy have been issued for seventy percent (70%) of the lots; or there being less than ten (10) unoccupied lots remaining within the development or as determined by the responsible official.
D. Contractor Certification.
Effective January 1, 2001, all development activities performed by licensed contractors shall be supervised by an individual who shall have successfully completed formal training in erosion and sediment control during construction by a recognized organization acceptable to the responsible official. A certification of successful completion of such training shall be submitted at the pre-construction conference. This shall not apply to residential homeowners constructing their own development activity.
E. Financial Liability.
The owner constructing the facility shall maintain a liability policy in the amount of five hundred thousand dollars ($500,000) which shall name Clark County, Washington, as an additional insured, and which shall protect Clark County from any liability up to that amount for any accident, negligence, failure of facilities, or any other liability whatsoever, relating to the construction or maintenance of the facilities. The liability policy shall be maintained by the owner of the facilities commencing at the start of construction and continuing until final acceptance. The responsible official may approve other forms of surety.