Construction activities can contribute excessive amounts of sediment into the public stormwater drainage system, lakes, streams, and wetlands. This can lead to the following problems:
- Pipes and ditches plugged by sediment are costly to clean, and can cause flooding and property damage.
- Excessive amounts of sediment in streams degrades aquatic habitat and inhibits salmon activities like predation and spawning.
- Excess nutrients in sediment cause growth of milfoil, algae, and other vegetation which decreases the recreational use and enjoyment of our waterways.
Only clean stormwater can be allowed to enter the storm drainage. To report an erosion control problem, fill out the Drainage & Water Quality Report form.
To protect adjacent properties and sensitive areas, development projects in the City of Kirkland are required to have a temporary erosion and sediment control (TESC) plan containing tools to be used to limit the amount of sediment leaving the construction site. Development erosion control requirements are located under Core Requirement #5: Erosion and Sediment Control, in the 2009 King County Surface Water Design Manual (KCSWDM). The ESC plan and report addresses the following elements:
- Clearing limits
- Soil cover measures
- Perimeter protection
- Traffic area stabilization
- Dust control
- Sediment retention
- Surface water control
- Dewatering control
- All projects meeting the threshold for a stormwater review require an ESC Plan, which includes both a site plan and a narrative report. The site plan shows the location and details of all ESC measures, and the report contains additional directions and supporting information (such as a detailed construction sequence, calculations, etc.). The level of detail will vary based on the size and scope of the project. Requirements of small site ESC Plans are located in Appendix D of the 2009 KCSWDM. Large sites can use the guidelines detailed in the PW Pre-Approved Plans Policy D-12.
- The applicant must designate an ESC supervisor. For projects 1 acre or larger, the ESC supervisor must be a Certified Erosion and Sediment Control Lead (CESCL).
- Projects 1 acre or larger are required to prepare a Storm Water Pollution Prevention and Spill (SWPPS) Plan, which addresses construction related pollution-generating activities. guidelines for the SWPPS Plan are located in the PW Pre-Approved Plans Policy D-12.
- Erosion control standard details are located in the PW Pre-Approved Plans.
- The ESC Plan and SWPPS Plan (if applicable) must be kept on site during all phases of construction.
- For projects that clear 2,000ft2 or greater, the City may require the ESC Supervisor to have a turbidity meter onsite and use it to monitor surface and stormwater discharges into onsite wetlands, streams, or lakes whenever runoff occurs from onsite activities and during storm events.
- Construction sites must have a minimum of 3 ESC inspections by City staff:
- ESC Inspection #1: Required prior to pouring concrete for foundation and footings.
- ESC Inspection #2: Required after foundation backfill, rough site grading, and prior to subfloor framing inspection. The subfloor framing inspection will NOT be conducted until the ESC inspection has been successfully completed.
- ESC inspection #3: Required for final site stabilization. A final building department inspection and sign-off will not occur until the final ESC inspection has been successfully completed.
- To schedule an ESC inspection, please call the Public Works Inspection Line at (425) 587-3805.
During construction, it may be necessary to pump groundwater or excess stormwater away from the site. This water can be contaminated with pollutants (including sediment) and cannot be discharged directly into the street or down a storm drain. The following dewatering options are available:
1) Pump the excess water to another area of the site, and allow it to infiltrate into the soil.
2) If infiltration is not possible, water can be temporarily pumped to a storage facility (like a pond or tank) to allow settling prior to discharge. this water can be discharged into the sanitary sewer only if authorized by King County.
For specific requirements to discharge into the sanitary sewer, refer to the KC Fact Sheet & Construction Dewatering Request Form.