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„,„ <br /> flG P 17311-135”'Ave, N.E.Suite A-500 <br /> '! fZI NELSON GEOTECHNICAL Woodinville,WA 98072 <br /> (425)486-1669 <br /> ASSOCIATES. INC, www.nelsongeotech.corn <br /> MEMORANDUM <br /> DATE: March 9, 2020 <br /> ft:9 M.S11 <br /> oe wA <br /> TO: Brian and Candice Aikins / <br /> FROM: Khaled M. Shawish, PE 35215 a ;� <br /> Lee S. Bellah, LG <br /> •ONAL <br /> RE: Supplemental Geotechnical Engineering Comment Memorandum <br /> Aikins Residence Development Stormwater Infiltration <br /> 2203—124th Avenue SE <br /> Everett,Washington <br /> NGA Job No. 1035918 <br /> INTRODUCTION <br /> This memo presents our response to review comments raised by the City of Everett regarding the <br /> proposed Aikins Residence Development project located at 2203 — 124th Avenue SE in Everett, <br /> Washington. <br /> We previously prepared a stormwater infiltration evaluation for this project dated May 16, 2018. We <br /> understand that concerns have been raised by the City of Everett regarding geotechnical aspects of the <br /> proposed site development. We understand that the City of Everett has requested that our previous <br /> report be updated to the most current stormwater manual. In our previous report, we utilized the 2014 <br /> Department of Ecology Stormwater Management Manual for Western Washington, (2014 SWMMWW)to <br /> determine the design infiltration rate for the site infiltration facilities. As a part of our evaluation, we <br /> performed one PIT test per individual lot for a total of two PIT tests. <br /> We understand that Everett now utilizes the most recent 2019 Department of Ecology Stormwater <br /> Management Manual for Western Washington, (2019 SWMMWW)to determine the design of infiltration <br /> facilities. Both the 2014 and 2019 manuals require on-site infiltration testing consisting of the small Pilot <br /> Infiltration Test (PIT) be utilized to determine the long-term design infiltration rates. The PIT procedures <br /> are similar in both manuals. As a result, our on-site testing and recommendations provided in our <br /> previous evaluation were also consistent with the 2019 SWMMWW. We recommend that any on-site <br /> stormwater systems be designed and constructed in accordance to the 2019 SWMMWW. <br />