7000 HARDESON RD Geotech Report 2022-10-25

Geotechnical Engineering Report Community Transit Merrill Creek Operating Base 7100 Hardeson Road Everett, Washington February 28, 2018 RN File No. 3224-002A Page 10 • "Observations of areal extent and time of surface ponding, including local government or professional observations of high water tables, frequent or long durations of standing water, springs, wetlands and/or frequent flooding." The photos below were taken on June 21, 2017 after an extended period of dry weather. As you can see, there is water on the pavement surface. �'. �!:r-,.,ry awl ��11 f . t;i�4. d _^. µ/ 1 ti 't Y v 2r's .YY 3S.*Ir_ { vi.•Y'-Di ,Mtu c d4 In addition, the DOE present Site Suitability Criteria (SSC) in section 3.3.7 of Volume III. SSC-6 states "Waste fill materials shall not be used as infiltration soil media nor shall such media be placed over uncontrolled or non-engineered fill soils." The entire site is underlain by approximately 14 to 19 feet of uncontrolled fill as shown on the boring logs in Figures 4 through 21 of this report. In our opinion, the site is therefore not suitable for infiltration. Rain Gardens/Bioretention BMP 15.14: The infeasibility criteria for rain gardens are the same as for bioretention. This is discussed in DOE Section 7.4 in Volume V. Infeasibility criteria include: • "Where professional geotechnical evaluation recommends infiltration not be used due to reasonable concerns about erosion, slope failure, or downgradient flooding." o The reason behind this study was to find a solution to the water that is ponded on the asphalt surface year round. In our opinion, rain gardens should not be used because there are reasonable concerns about downgradient flooding from the rain gardens onto the adjacent pavement. Robinson Noble, Inc.