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GeoTest Services, Inc. Report Date 7/17/2019 <br /> Anderson Residence-Everett, Washington GTS Project No.19-0384 <br /> imionime max. <br /> The rates presented in Table 1 are representative of loose soil conditions and do not <br /> account for the denser soils encountered at depth. For small-scale infiltration facilities <br /> bottomed less than 5 feet below the existing ground surface, it is our opinion that a <br /> design infiltration rate of 5 inches per hour is appropriate for initial sizing of facilities. <br /> We should be contacted to review proposed infiltration facilities prior to construction, <br /> in case the nature or extent of these facilities varies from what we have anticipated. <br /> Storm water Treatment <br /> The stormwater facilities on-site may require some form of pollutant pretreatment <br /> with an amended soil prior to on-site infiltration or offsite discharge.The reuse of on- <br /> site topsoil is often the most sustainable and cost-effective method for pollutant <br /> treatment purposes. Cation exchange capacities, organic contents, and pH of site <br /> subsurface soils were also tested to determine possible pollutant treatment suitability. <br /> Cation exchange capacity, organic content, and pH tests were performed by <br /> Northwest Agricultural Consultants on two soil samples collected from our <br /> explorations.A summary of the laboratory test results is presented in Table 2 below. <br /> Table 2 <br /> Cation Exchange Capacity, Organic Content, and pH Laboratory Test <br /> Results <br /> Cation <br /> Sample Exchange Organic <br /> Test Pit Geologic <br /> Depth Capacity Content pH <br /> ID Unit <br /> (ft) (meq/100 (%) <br /> grams) <br /> HA-2 0.5 Topsoil 14.2 4.88 7.0 <br /> HA-3 1.0 Relict 11.4 3.56 6.4 <br /> Suitability for onsite pollutant treatment is determined in accordance with SSC-6 of <br /> the 2012 Washington State Department of Ecology Storm water Management Manual <br /> for Western Washington. Soils with an organic content greater than or equal to 1 <br /> percent and a cation exchange capacity of greater than or equal to 5 meq/100 grams <br /> are characterized as suitable for stormwater treatment. Based on the results shown <br /> in Table 2, soils within the upper 2 feet are suitable for stormwater treatment. <br /> On-site soils can be amended by mixing higher silt content soils or adding mulch (or <br /> other admixtures) to elevate the cation exchange capacity and organic contents. On- <br /> 16 <br />