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Geatecbthcal Ea_°ineeringElaluatian NGAFie Na.1031018 Multi-Faintly Regsleotial Dovelament Apol 19,2018 Everett,Washington Page 11 on the attached Schematic Site Plan in Figure 2. The subsurface soils generally consisted of silty fine to medium sand with gravel,which we interpreted as native,glacial soils. Infiltration Pit One:We conducted a Small PIT within infiltration Pit One,as shown on the Schematic Site Plan in Figure 2.The test was conducted within a pit that measured 3.6=feet long by 5.0-feet wide by 3.0-feet deep:We filled thepit with.12-inchesofwater at thee beEieninnnf the day and were able to maintain the water level for the duration of the soaking period for approximately houm.At this time,the water flow rate into the hole was monitored with a Great Plains Industries(GPI)TM 075 flow meter for the pie-soak period Aftertbe 6-hour soaki P penodwas completed,the water level was maintained at 12.0-inchm for one hour for the steady-state period. The flow rate for Infiltration Pit Two stabilized at 0.86 gallons per mimite(51..6 gallons per hour).This equated to an approximate infiltration rate of 4.60 inches per hour. The water was shut off after the steady-state period and monitored at least every 15 minutes for an hone.. At the end of the monitoring period,the water level within the pit had dissipated by 3.0 inches,resulting in an infiltration rate of3.0 inches per hour. infiltration Pit Two:We conducted a Small PIT within Infiltration Pit Two.as shown on the Schematic Site Plan in Figure 2.The test was conducted within a pit that. smed 3.6-feet long by 5 2_feet wide by 3.0-feet deep.We filled thepit with 12-inches of water at the befinninf of the day and were able to maintain the water level for the duration of the soaking period for approximately 6 hours.At this time.the water flow rate into the hole was monitored with a Great Plains Industries(GPI)TM 075 flaw meter for the pie-soak period. After the 6-hour sea/MT period_was completed,the water level was maintained at approximately 12-inches for one hour for the steady-state period:. The flow rate for Infiltration Pit Two stabilized at 1.77 gaols per minute(106.2 gallons per hour).This equated to an approximate infiltration rate of 9.10 inches per hour. The water was shut off after the steady-state period and monitored at least every 15 minutes for approximately two and a half hours. At the end of the monitoring period,the water level within the pit had dissipated by 6.25 inches.resulting in an infiltration rate of 2.5 inches per hour. Long Term Rate:In accordance with the Table 3.5 of the Department of Ecology 2014 SWMMWW, correction factors of 0.8,0.5,and 0.9 for GFv,CFt,CFm,respectively were applied to the field measured infiltration rate of 3.0 and 2.5 inches per hour,obtained from the falling-head portion of the testing in infiltration Pits One and Two,respectively. A total correction factor of 036 was applied to the measured field infiltration rates obtained from the falling head portion of the tests to determine the long-term desipi infiltration rates. NELSON GEOTECHNICAL ASSOCIATES,INC. 28