All construction projects in Kent that disturb one acre of soils or greater are required to develop and submit a Stormwater Pollution Prevention Plan (SWPPP) to the city. The SWPPP includes site specific best management practices (BMPs) for reducing or eliminating pollution in stormwater before it leaves the site. The SWPPP’s proposed BMPs must be reviewed prior to permit approval and are required to be continuously inspected during construction in order to reduce erosion potential on the site and to protect water quality.
A complete SWPPP will focus on 12 main elements that have the potential to affect stormwater and water quality. These 12 elements include:
1. Preserve Vegetation & Mark Clearing Limits
2. Establish a Construction Access
3. Control Flow Rates
4. Install Sediment Controls
5. Stabilize Soils
6. Protect Slopes
7. Protect Drain Inlets
8. Stabilize Channels and Outlets
9. Control Pollutants
10. Control De-Watering
11. Maintain BMPs
12: Manage the Project
The city’s stormwater management standards are stipulated in a combination of city codes, city standards, and adopted standards from other agencies. More information on these requirements can be found below.
Design & Construction Standards BMP Activity Sheets BMP Information Sheets Surface Water Design Manual
How to do Stormwater Monitoring: A guide for Construction Sites
Single Family Home Brochure: Erosion and Sediment Control
In addition to developing and implementing a SWPPP, all construction sites disturbing greater than one acre of soil are also required to conduct periodic inspections of their site to verify that the proposed BMPs are adequately protecting the site from erosion and sediment control issues. It is required that every construction site has a Certified Erosion and Sediment Control Lead (CESCL) who conducts the required inspections. A CESCL is a person who has current certification through an approved erosion and sediment control training program. The Washington State Department of Ecology (Ecology) approves these courses and keeps and updated list of current classes on their website which can be accessed here.
In September and October of 2012, the City of Kent provided CESCL recertification to 40 city staff.
why is stormwater and water quality affected by development?
The water cycle, also known as the hydrologic cycle, describes the continuous movement of water on, above and below the surface of the earth. In areas that are not developed, most rain and snow fall either infiltrates into the ground or is absorbed by the vegetation. Water that infiltrates into the ground will eventually make its way to surface waters such as wetlands, creeks or rivers through the ground or springs. Water absorbed by vegetation cycles back into the atmosphere through evapotranspiration. The benefits of this process include: pollutant removal, temperature reduction, erosion control, groundwater recharge, flood and draught control, wildlife habitat, recreation and increased property values.
Construction and development affect stormwater through an increase in impervious surface space. Stormwater cannot infiltrate into the ground and falls directly onto surfaces such as roadways, construction sites or industrial sites, collecting various pollutants and discharging directly into surface waters without treatment. Increased impervious surfaces cause the quantity of stormwater runoff to increase as well. Lack of treatment and increased run off can cause many water quality related issues such as pollutant loading, erosion of streambeds and channels, sedimentation in streams, creeks, rivers and other waterbodies, habitat loss and flooding.
Ecology Issues the New 2010 Construction Stormwater General Permit!
Ecology issued the 2010 Construction Stormwater General Permit on December 1, 2010. The previous permit, the 2005 Construction Stormwater General Permit was set to expire on December 16, 2010. Read about the significant changes that were made to the new permit.
Department of Ecology's Stormwater Website
Construction sites in Washington State are required to be covered by a Construction Stormwater General Permit through the Department of Ecology if they are engaged in clearing, grading, and excavating activities that disturb one or more acres and discharge stormwater to surface waters of the state. Smaller sites may also require coverage if they are part of a larger common plan of development that will ultimately disturb one acre or more. Operators of regulated construction sites are required to develop stormwater pollution prevention plans as well as implement sediment, erosion, and pollution prevention control measures.
Ecology's Notice of Application
WA Stormwater Technical Resource Center Website
The Washington Stormwater Technical Resource Center offers stormwater management assistance to Washington NPDES permittees and stormwater managers by providing access to information, training, permit assistance, research and emerging technologies. The Washington Stormwater Technical Resource Center is a joint venture between WSU-Puyallup Research and Extension Center and University of Washington, Tacoma Center for Urban Waters.