SITE INFORMATION AND CORRESPONDENCE

Home Browse Search

0. s STATE OF CALIFORNIA—ENVIRONMENTAL PROTECTION AGENCY ~� PETE WILSON,Govwwr CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD— i " ,-_,, CENTRAL VALLEY REGION t"V_1AVNxE. TAL N�A1 TSI 3443 ROUTIER ROAD,SUITE A Ir ${r ;� u�(;E I SACRAMENTO,CA 95827-3098 9 ;e / PHONE: (916)255-3000 6 .IUB. j 2 AM 10: 32 FAX: (916)255-3015 11 July 1996 Mr. Tom Welch Westrec Properties 116633 Ventura Blvd., 6th Floor Encino,CA 91436 REVIEW OF FIRST QUARTER 1996 GROUNDWATER MONITORING REPORT, TOWER PARK MARINA, 14900 W. HIGHWAY 12, LODI (SAN JOAQUIN COUNTY) Staff reviewed the First Quarter 1996 Groundwater Monitoring Report submitted on behalf of Tower Park Marina by SECOR International in accordance with Monitoring and Reporting Program (MRP)Order 95-802. The report shows that increases in hydrocarbon concentrations have been detected in several wells, and that compared to December 1995 readings,ground water levels have risen. Groundwater at the site continues to flow away from Potato Slough and to differ from the regional gradient.Free product has been reduced to a sheen in MW-3,but dissolved concentrations are reported at 16,000 gg/L TPH-d and 320 µg/L TPH-g. This is an increase from 4000µg/L TPH-d and ND TPH-g over December 1995 levels. Increased concentration of TPH-d in MW-2 and MW-4 also are reported. The increase in MW-2 was from ND in December 1995 to 90µg/1-in March . MW-2 regularly varies from ND to low levels of diesel. A slight increase in xylene was reported in MW-4. Additionally, 1.4µ/L toluene was detected in MW-4 and 90µ/L TPH-d was reported from MW-5. These are the first detections of these compounds in these wells since June 1993. MW-5,a cross-gradient well,has had no detections of any hydrocarbons since 1993. We believe that these results indicate redissolving of residual hydrocarbons in the vadose zone as a result of the rising water table. The increases occurred even though dissolved oxygen levels increased in all the wells except MW-4,which may inndicate that significant biological activity is not occurring. Other issues: Field Protocols: As discussed via telephone with SECOR staff on 8 July, we had some concerns about the field procedures involving the wells containing ORC socks. Staff noticed that the field notes accompanying the report state that depth to water measurements were taken with the ORC socks in place in place in wells MW-2,-3,and-4. Since the socks are 2 inches in diameter and are arranged in a string of five placed in a 2-inch diameter well, with the top sock initially placed at the water surface, it is not clear how in-well measurements could be taken with reliable results.Staff assumed that the socks were removed after the initial depth to water measurements were taken, and before other procedures were performed. The telephone discussion confirmed this. Future reports should contain a summary of field protocols that specifies and clarifies actual