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. Report an erosion control problem via the Our Kirkland Customer Service Portal.
To protect adjacent properties and sensitive areas, development projects in the City of Kirkland (City) 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: Construction Stormwater Pollution Prevention, in the current version of the King County Surface Water Design Manual (KCSWDM). The TESC plan and report addresses the following elements:
- Clearing limits
- Cover measures
- Perimeter protection
- Traffic area stabilization
- Sediment retention
- Surface water collection
- Dewatering control
- Dust control
- Flow control
- Control pollutants (see SWPPS Measures in KCSWDM)
- Protect existing and proposed flow control BMPs
- Maintain BMPs
- Manage the Project and Final stabilization
- All projects meeting the threshold for a stormwater review require an TESC Plan, which includes both a site plan and a narrative report. The site plan shows the location and details of all TESC 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 TESC Plans are located in Appendix D of the current version of the KCSWDM and in the City's Pre-Approved Plans Policy D-12.
- The applicant must designate a CSWPP supervisor. Refer to the CSWPP Performance and Compliance Provisions in the current version of the KCSWDM to determine if additional qualifications are required of a CSWPP supervisor.
- Projects disturbing 2,000 square feet or greater 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 Appendix D of the current version of the KCSWDM and in the City's Pre-Approved Plans Policy D-12.
- Erosion control standard details are located in the City's Pre-Approved Plans.
- The TESC Plan and SWPPS Plan (if applicable) must be kept on site during all phases of construction.
- The City may require the CSWPP 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 TESC inspections by City staff:
- TESC Inspection #1: Required prior to pouring concrete for foundation and footings.
- TESC 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 TESC inspection has been successfully completed.
- TESC inspection #3: Required for final site stabilization. A final building department inspection and sign-off will not occur until the final TESC inspection has been successfully completed.
- To schedule an TESC inspection, please call the Public Works Inspection Line at (425) 587-3805.
- If a City Staff Member or bystander reports a potential illicit discharge to the City, the City may conduct an additional inspection to enforce BMP updates in order to reduce sediment-laden runoff. This may occur for each incident reported to the City.
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 unless certain criteria are met. 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.
Refer to Policy E-1 of the City of Kirkland Pre-Approved Plans for approved methods in construction dewatering.
For specific requirements to discharge into the sanitary sewer, refer to the KC Fact Sheet & Construction Dewatering Request Form.