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W-05-97 FRI 03:14 PM P, 02/08 <br /> i <br /> 3164 Gold Camp Drive <br /> Delta suite 200 <br /> Rancho Cordova,CA 95670 <br /> Environmental <br /> AR/Ak Consultants, 916163&2085 <br /> Inc. FAX'8161638.8..85 <br /> September 4, 1997 <br /> Ms.Mary Meays <br /> San Joaquin County Department of Public Health Services <br /> Environmental Health Division <br /> 304 East Weber Avenue <br /> Stockton, California 95201-388 <br /> Subject.: Addendum to Revised Work Plan for Ort-Site Assessment <br /> Holz Rubber Company <br /> 1129 South Sacramento Street <br /> Lodi,California <br /> Delta Project No. D096-090 <br /> Dear Ms. Meays: <br /> This letter is in response to your telephone conversation this morning with Mr. Eric Hohn regarding the <br /> proposed activities at the subject site (Figure 1). In said conversation you requested additional information <br /> regarding construction details for the proposed ground water monitoring wells,backfill derails on the proposed <br /> geoprobe,hand auger, and soil vapor probe borings,and treatment of soil generated during drilling activities. <br /> The following information is provided as an addendum to Delta Environmental Consultants, Inc-'s Revised <br /> Work Plan for On-site Assessment,dated June 30, 1997. <br /> Ground Water Mouitorine Well Construction Details <br /> The six proposed ground water motutoriag wells will be constructed of 2 inch diameter, flush-threaded, <br /> Schedule 40 PVC casing. The monitoring wells will be screened with 0.020 inch slotted screen <br /> extending from approximately 45 to 70 feet below surface grade (bsg) to allow for seasonal ground <br /> water table fluctuations. The atmular space in each well will be filled with a filter pack consisting of <br /> No. 3 Lonestar sand from 2 feet above the well screen to the maximum depth of each well. A 2 foot <br /> thick bentonite transition seal will be placed above the filter pack. If ground water is present in the <br /> borehole at the depth of the bentonite seal,the bentonite(Wyo-Ben Eavirplug medium)will be installed <br /> using a tremie pipe. The annular space above the bentonite seal will be filled with neat cement grout <br /> T=ed at a ratio of one 94 pound sack of Portland cement to bmnen 5 and 10 gallons of potable <br /> water. The neat cement grout will be placed in the annulus using a tremie pipe up to a depth of 30 feet <br /> bsg; from 30 feet bsg to the ground surface, the grout will be installed via gravity from the ground <br /> szuface. A proposed construction detail for the monitoring wells is included in Enclosure A. The <br /> location of the wells is illustrated in Figure 2. <br /> Destruction of Geoprobe and Hand Auger Soil Borin£s. and Soil Vapor Probe Borings <br /> The geoprobe and hand auger soil borings, and soil vapor probe borings will be backfilled with neat <br /> cement grout mixed at a ratio of one 94-pound sack of Portland cement to 5 to 10 gallons of potable <br /> water. Since the interval to be backfilled is anticipated to be dry and less than 30 feet in depth,the neat <br /> gement grout will be installed via gravity from the ground surface. If ground water is encountered in a <br /> Providing a Competitive Edge <br />