10627 19TH AVE SE COOLEY SMILES DENTISTRY 2019-03-18

Geotechnical Engineering Evaluation NGA File No. 1008917 Cooley Smiles Commercial Development October 3,2017 Everett,Washington Page 12 Infiltration Pit 1: Infiltration Pit 1 was located within the northern parcel and measured 3.6 feet long by 5.3 feet wide, by 3.3 feet deep. The hole was filled with approximately 12.0 inches of water and this level was maintained for six hours for the pre-soak period. At the end of the pre-soak period, the water flow rate into the hole was monitored with a Great Plains Industries (GPI) TM 075 water flow meter for one hour. After the 6-hour soaking 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 1 stabilized at 0.20 gallons per minute (12.0 gallons per hour). This equated to an approximate infiltration rate of 1.01 inches per hour. The water was shut off after the steady-state period and monitored at least every 15 minutes for one hour. After 60 minutes, the water level within the pit had decreased to 11.0 inches, resulting in an infiltration rate of 1.0 inch per hour. Infiltration Pit 2: Infiltration Pit 2 was located within the central property and measured 3.5 feet long by 6.0 feet wide,by 3.4 feet deep.The hole was filled with approximately 12.0 inches of water and this level was maintained for six hours for the pre-soak period. At the end of the pre-soak period, the water flow rate into the hole was monitored with a Great Plains Industries (GPI) TM 075 water flow meter for one hour. After the 6-hour soaking 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 2 stabilized at a rate of 0.17 gallons per minute (10.2 gallons per hour). This equated to an approximate infiltration rate of 0.78 inches per hour. The water was shut off after the steady-state period and monitored at least every 15 minutes for one hour. After 60 minutes, the water level within the pit had decreased to 11.25 inches, resulting in an infiltration rate of 0.75 inch per hour. Infiltration Pit 3: Infiltration Pit 3 was located within the southern property and measured 3.0 feet long by 4.0 feet wide by 3.5 feet deep. The hole was filled with approximately 12.0 inches of water and this level was maintained for six hours for the pre-soak period. At the end of the pre-soak period,the water flow rate into the hole was monitored with a Great Plains Industries (GPI) TM 075 water flow meter for one hour. After the 6-hour soaking 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 3 stabilized at a rate of 0.07 gallons per minute (4.2 gallons per hour). This equated to an approximate infiltration rate of 0.56 inches per hour. The water was shut off after the steady-state period and monitored at least every 15 minutes for one hour. After 60 minutes, the water level within the pit had decreased to 11.625 inches, NELSON GEOTECHNICAL ASSOCIATES,INC.