Resolution 7270 - Laserfiche WebLink

Executive Summary The City of Everett manages a surface water system, referred to herein as the Surface Water Service Area (SWSA), to protect and enhance the City's surface waters. The SWSA includes more than 11,000 acres in the southern portion of the City comprising 20 major drainage basins. The SWSA is managed by the Surface Water Program in the Public Works Department, and is the planning area for this Surface Water Comprehensive Plan (SWCP). The SWSA's stormwater component is the City's Municipal Separate Storm Sewer System (MS4), which is a network of conveyances such as pipes and ditches, flow control facilities such as detention ponds, and water quality facilities that carry and treat surface runoff from developed areas. The City operates and maintains the MS4 to prevent adverse impacts from the current and past effects of land development, such as increased flow rates and stormwater pollution.' The SWSA's surface water component consists of natural surface water features within the City. These streams, rivers, and lakes—including Puget Sound and the Snohomish River—receive drainage from adjacent lands and the MS4, and also may be altered through the installation of controls, such as culverts. An original set of basin plans for surface water management, called the South Everett Drainage Basins Plan, was prepared for the City's surface waters in 1982. Since then stormwater science has advanced, state and federal regulations have changed, and the City has grown through annexations, population growth, and urbanization. These changes led to the City's desire to update the older basin plans and to develop a framework for identifying issues and solutions in the SWSA. The SWCP, developed over several phases under the guidance of City staff in the Public Works and Planning Departments, provides the framework and recommends capital projects and programs intended for a 10-year planning period. Surface Water Issues Surface water includes waterbodies across the landscape such as lakes, rivers, ponds, streams, and wetlands and also includes the runoff that occurs when precipitation falls on pervious or impervious surfaces and flows over surfaces and the ground, as opposed to infiltrating into soil. Stormwater runoff can cause a variety of adverse impacts in the urban environment and in those areas downstream of urbanized areas. Issues can be classified into three primary categories: adverse water flow, poor water quality, and degradation of stream channel or riparian (stream- side) habitat. Where surface water conveyance systems are not adequately sized to handle the volume of runoff directed to them, adverse water flow during storms may result, including inundation. Inundation is often seen where infrastructure such as culverts and ditches were constructed prior to more intensive urban development, or when stormwater facilities are no longer functioning as designed. Inundation issues can be corrected by resizing culverts, adding catch basins, and increasing the size of conveyance pipes or ditches. Poor water quality can also result from inadequate surface water controls. Sediment and other pollutants accumulate on impervious surfaces between storms and wash off into storm drains or directly into surface waters during storms. Increased rate and volume of stormwater runoff that 1 The City of Everett also operates a combined sewer, the North End Sewer System (NESS),which manages both wastewater(sewage)and stormwater together in a system that conveys effluent to the City's Water Pollution Control Facility. This system is different from the surface water system described in this document. City of Everett Surface Water Comprehensive Plan ES-1 Volume I—Summary and Implementation Plan November 2017