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• • Kenneth D. Landau -2- 16 June 1987 LLNL conducted limited post-closure ground water monitoring in the GSA at three water supply wells , Wells 18, 6, and 7. Wells 18 and 6 are about 1/4 mile west and Well 7 is about 150 feet east of the nearest drywell , respectively. No information was given on direction of ground water flow. Well 18 is screened beginning at 150 feet deep while the Well 6 and 7 screens begin at 42 and 60 feet, respectively. The first round of annual sampling was conducted in May 1985 and the results submitted in August 1985. Wells 6 and 7 contained 3 ppb and 2 ppb, respectively, of TCE. No further post-closure monitoring results have been submitted. Drywells 875-S2, 873-E, and 87/2-5 could pose a threat to water quality based on the analyses provided in the February 1983 closure plan. Sampling conducted during drywell closure was not adequate to determine if proper cleanup occurred. - We need construction details and samples directly from the bottom of these drywells to determine if additional cleanup is required. We also need a characterization of the wastewater discharged to drywell 874-N to decide whether additional actions are needed there. Drywells 875-S1 and 873-S can be considered closed with no further actions required based on the wastewater characterization. 2. Four drywells were closed in late 1985 (at Buildings 801, 8276, 835, and 8366) by plugging or capping drains and welding acid dip tank covers shut (the small tanks were built into a stainless steel counter and are no longer used. The acid was drained and the covers welded shut simply to provide additional counter space) . The characteristics of wastewater discharged to these wells in the past was not given nor were the results of any soil samples taken. If this rinse water is similar to the acid dip tank rinse water discharged to the GSA drywells 875-S2 and 873-E, these four wells could pose a threat to water quality. We need wastewater characterization, soil sample results , well construction details, and closure procedures used to make this determination. The drywell at Building 810 receives only floor was.hdown water to remove dust and dirt, not oil , according to the 14 April 1987 letter. A sample of this washwater should be taken and analyzed for oil and grease and any other constitutents likely to be present based on the operations at that building to corrob6- rate the statement. 3. Drywells at Buildings 813, 815, and 827A receive cooling tower discharge with 813 on standby only, according to a 30 September 1985 letter from LLNL. That letter also states that 815 and 827A are permitted by Order 82-105. However, that order does not mention drywells, rather it permits cooling tower discharge to surface water. Use of the drywells for cooling tower discharge is acceptable and should be written into the new permit if LLNL wishes to continue using them for that purpose (a Report of Waste Discharge was submitted 20 April 1987 for NPOES permit renewal ) .