5406 S 1ST AVE 2021-02-25 - Laserfiche WebLink

NELSON GEOTECHNICAL NGA ASSOCIATES, INC. GEOTECHNICAL ENGINEERS & GEOLOGISTS Main Office Engineering-Geology Branch. 17311---135th Ave NE,A-500 5526 Industry Lane,#2 Woodinville,WA 98072 East Wenatchee,WA 98802 (425)486-I669 FAX(425)481-2510 (509)665-7696•FAX(509)665-7692 June 20,2018 Mr.Melvin Gay 5629- 151St Place SW Edmonds, Washington 98026 Stormwater Infiltration Letter Zillah Street Residential Development Infiltration Zillah Street Everett,Washington NGA Job No. 1040718 Dear Mr. Gay: This letter documents our explorations and provides our opinions and recommendations for the feasibility of stormwater infiltration stormwater infiltration evaluation of the proposed residential development project located along the southwest corner of the intersection of Zillah Street and lst Street in Everett, Washington as shown on the Vicinity Map in Figure 1. The parcel numbers for the properties are 00500302700100(northern parcel)00500302700200(southern parcel)., INTRODUCTION The site consists of two separate vacant parcels situated to the south and west of Zillah Street and 1st Street, respectively. The ground surface within the site generally slopes gently down from the western property line along an alleyway to the eastern property line along 1st Street. We understand that the proposed development plan will consist of constructing a new single-family residence within each property. Specific grading and stormwater plans were not available when this proposal was prepared, but we understand that stormwater may be directed to on-site infiltration facilities, 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.