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2.3 Soils Based on the Natural Resources Conservation Service-Soil Survey of Snohomish County,the on- site soils consist of Alderwood Urban Land Complex, which is classified as a"C"hydrologic soil type. A copy of the soil survey and a detailed description is provided in Appendix B. 2.4 Ground Cover In the vicinity of the track and field, the ground cover consists of primarily grassy areas with a cinder track. South of the project site, the area surrounding several storage buildings is paved with asphalt, which is located outside of the construction limits and will not be disturbed. Similarly, a short concrete walk borders the southeast portion of the track and will not be affected by construction activities. 2.5 Critical Areas There are no known critical areas within or adjacent to the project site. 2.6 Adjacent Areas See Section 1.1 —General Project Description for discussion of adjacent areas. 3.0 SITE DEVELOPMENT PLAN AND MINIMUM REQUIREMENTS SUMMARY The conditions and requirements for the project are reviewed in this section and will address the minimum requirements stipulated in the City of Everett 2010 Stormwater Management Manual. 3.1 Applicability of Minimum Requirements Over the years, the existing cinder track has been compacted through repetitive use and exposure to weather such that it reacts similarly to an impervious surface during storm events. There is often ponding water observed on the track immediately following a storm. To maximize the use of on-site natural stormwater management practices, the new track and "D" areas have been designed using a synthetic rubber surface that allows infiltration of stormwater. In addition,the underlying base includes permeable asphalt paving to allow water to pass through to native soils (See Appendix B for supporting product data and specifications). The large surface area of the track and "D" areas should allow considerable infiltration, which should reduce the flow and volume of runoff to downstream systems. The City of Everett and the Department of Ecology have not identified a formal process for designating Low Impact Development (LID) credits. However, Table 5.2.2.A Flow Control BMP Facility Sizing Credits of the 2009 King County Surface Water Design Manual, which is often regarded as an equivalent standard to local drainage codes, provides credit for the use of permeable pavements and surfaces. According to the King County manual,permeable pavements can be considered as 50% impervious and 50% pervious. The 2005 Low Impact Development Technical Guidance Manual for Puget Sound also uses the same credit for permeable pavements. Excerpts from both manuals are provided in Appendix B. Using these guidelines, a summary of the existing and proposed impervious area calculations is provided in Table 1 (See Appendix B for site plan,calculations,and associated areas). Technical Information Report Cascade High School—Track Replacement Project 2 Integrityworks Consulting Engineers,LLC Project No.212104