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Fox Loomis, Inc. <br /> 6901 McComber Street, Sacramento, CA 95828 <br /> TEL: (916) 383-2140, FAX: (916) 383-8021 <br /> December 11, 2008 <br /> San Joaquin County <br /> Environmental Health Department <br /> 600 E. Main Street <br /> Stockton, CA <br /> Dear Margaret Lagorio, <br /> Re: Work Plan for 6 ea monitoring wells for Contra Costa Water District pump station site at 21000 <br /> Hwy 4, Holt, CA, Fox Job No: 08-497, P-101, P-102, P-103, P-104, P-105, P-106 <br /> The six each monitoring wells are to monitor the groundwater elevation around the new Contra Costa <br /> Water District Pump Station on Victoria Island during construction. The site is approximately 8,400 feet <br /> south of highway 4. The site is at elevation plus 18. <br /> The site has been investigated by the district and it has no hazardous or contaminated materials on the <br /> site. <br /> The monitoring wells will be 58' deep they will be drilled with an 8" hollow stem drill. They will have 2" <br /> schedule 40 PVC casing. The well screen will have 0.020" slots with a screen interval from 53' to 58' <br /> in depth. Wells will have blank well casing from 53' deep to grade. Well filter gravel will be #2/12 sand <br /> from 51' to 58' in depth. Wells will have a bentonite transition seal from 51' to 48" in depth. Sand <br /> cement slurry seal from 48' in depth to grade. At the well head 2" well casing will have a locking <br /> expansion plug with a brass padlock. The wellhead will be covered with metal vault 8" diameter by 12" <br /> deep with a casketed surface bolt down 8" diameter lid with H-20 load capacity. The monitoring well <br /> will have a 2' long by 2' wide by 4" thick concrete surface pad. <br /> Work crew will meet all applicable safety requirements and wear the following safety equipment, <br /> hardhat, safety glasses, durable work boots, and safety vest or safety shirt. <br /> When groundwater level monitoring is no longer needed for this site, these monitoring wells will be <br /> destroyed by pump tremie placing neat cement full depth. The neat cement sealing material will be <br /> pressurized to 5 psi. Additional makeup neat cement slurry will be added until the well will not take any <br /> more sealing material. After the neat cement slurry has set the surface pad, well surface box and the <br /> top 5' of the 2" PVC casing and well seal will be removed. A neat cement cap will be placed over the <br /> top of the well casing and the well seal. The 5' deep hole will be backfilled with native soil. <br /> If you have any questions please call. <br /> Very Truly Yours, <br /> Arnold Zwankhu e <br />