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NELSON GEOTECHNICAL M• A ASSOCIATES, INC. GEOTECHNICAL ENGINEERS & GEOLOGISTS Main Office Engineering-Geology Branch 17311-I35'h Ave NE,A-500 5526 Industry Lane,#2 Woodinville,WA 98072 East Wenatchee,WA 98802 (425)486-1669•FAX(425)481-2510 (509)665-7696 FAX(509)665-7692 May 16,2018 Brian and Candice Aikins c/o Sarah Thompson Fred Baxter&Associates 649 Fifth Street, Suite 203 Mukilteo,Washington 98275 Stormwater Infiltration Letter Aikins Residence Development Stormwater Infiltration 2203—124th Avenue SE Everett,Washington NGA Job No. 1035918 Dear Mr. and Mrs.Aikins: This letter documents our explorations and provides our opinions and recommendations for the feasibility of stormwater infiltration at the residential property development project located at 2203 — 124`h Avenue SE in Everett,Washington, as shown on the Vicinity Map in Figure 1. The parcel numbers for the two properties that make up the subject development are 28052900204100(northern parcel)and 28052900203900(southern parcel). INTRODUCTION The southern property is currently occupied by an existing single-family residence while the northern property is currently occupied by detached shed structures. The ground surface within the properties is generally relatively level to gently sloping from the north to the south. We understand that the proposed development plan will consist of removing the existing single-family residence and constructing a new single-family residence and detached garage within the northern property. Specific grading and stormwater plans were not available at the time this proposal was prepared. However, we understand that stormwater is likely to be directed into on-site infiltration systems, if feasible. We have been requested to evaluate the infiltration capacity of the site soils. The City of Everett uses the 2014 Department of Ecology Stormwater Management Manual for Western Washington, (2014 SWMMWW) to determine the design of infiltration facilities. According to this manual,on-site infiltration testing consisting of the small Pilot Infiltration Test(PIT)is used to determine the long-term design infiltration rates. As a part of our evaluation,we performed one PIT test per individual lot for a total of two PIT tests.