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*MEMORANDUM CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD- CENTRAL VALLEY REGION 3443 Routier Road Phone: (916) 361-5600 Sacramento, CA 95827-3098 ATSS Phone: 8-495-5600 TO: Greg K. Vaughn FROM: Camilla K. Williams Senior Engineer ` Engineering Geologist DATE: 8 November 1989 SIGNATURE: SUBJECT: GROUNDWATER ASSESSMENT REPORT, KEARNEY-KPF, SAN JOAQUIN COUNTY - FILE NO. 73 I have reviewed the 29 September 1989 Groundwater Assessment Plan submitted by Hargis and Associates for Kearney-KPF. Overall , the report is acceptable, is detailed, is well prepared and documented and is comprehensive. The data summarizations and graphics (tables, graphs and cross-sections) are thorough and exemplary. However, I have three major concerns with the report which are summaryzed below. More detailed, and minor comments can be found in the attachment. The first major concern is with monitoring well screen length. In the past, saturated screen lengths of only ten feet have been used. However, the continued use of this screen length is not technically justified (especially for the shallow portions of the upper aquifer) , in view of the recent historical documented water table decline of over ten feet per year. In addition, the use of short screen lengths which do not fully penetrate the water bearing zone to be pumped during an aquifer test causes an increase in head loss and a decrease in yield, and if mathematically uncorrected can cause aquifer parameters to be underestimated. Furthermore, if the aquifer continues to dewater, then additional shallow monitoring wells may need to be reinstalled in known areas of Volatile Organic Constituent (VOC) contamination for the duration of the remedial investigation and ground water cleanup phases. The second concern is with the proposal for additional work in Phase II of the Hargis remedial investigation. Their proposals to install additional monitoring wells to define the full areal extent of volatile organic contamination in ground water seems excessive. The installation of fewer wells more strategically located is more cost effective and may provide enough information to adequately contour the VOC plume. Hargis has also proposed collection of soil samples from beneath the water table for VOC analyses. However, this appears unnecessary as VOCs are present in the ground water. Lastly, Hargis has proposed abandonment of the two on-site supply wells. I agree that these wells should be abandoned as the data indicate that they may be conduits for contamination of lower water bearing zones. However, the proposal was inadequate. To properly abandon these wells, not only must the annular space be filled, but a minimum of a 20 foot seal must be placed inside the upper portion of the casing in accordance with State of California Water Well Standards. The proposal did not provide detail on how the abandonment will be performed, and the slurry design may be inappropriate for the well conditions. Whether or not Hargis amends their abandonment proposal , I strongly recommend that a cement bond log or similar purpose log should be conducted to demonstrate that a complete cement sheath has been placed in the annulus.