SITE INFORMATION AND CORRESPONDENCE

Home Browse Search

• ATTACHMENT . 1. P. 11 In general , the cross-sections, A-A' and B-B' (Figures 6 and 7) are exemplary. Lithology, correlations, well screen intervals and water levels are clearly depicted. 2. p. 13 There is a discrepancy between the driller's log (lithologic log in Table A-1) and the electric log from KSH-2 in the interval between approximately 65 and 105 feet in depth. The lithologic log has this interval described as clay with a trace of sand. However, the electric log (both self-potential (SP) and resistivity) and cross-section A-A' have this interval depicted as a sandy horizon within the intermediate zone of the upper aquifer. The electric logs show three distinct sandy layers interbedded with clayey layers. 3. p. 13 It is interesting to note that the SP logs from cluster sites K-4 and K-5 support the analytical results for standard minerals from the respective intermediate and deep wells. The strong SP response (more negative) , other than indicating lithologic type, also indicates relative saline conditions. The analytical results for bicarbonate, calcium, chloride and total dissolved solids (TDS) have roughly double the concentrations from KI-4 and KI-5 versus the respective concentrations from KD-4 and KD-5. 4. p. 13 Although not crucial to the remedial investigation, I do not concur with the grouping of the one to 20-foot thick gray to gray brown silty clay, sandy clay and silt with the deep zone gravel rather than with the blue- gray unit. The thin gray-brown silty clay layer is geologically and hydrogeologically more similar to the blue-gray unit. Both of these layers/units tend to represent lower-energy depositional environments versus the higher-energy depositional environment of the deep gravel zone, and these layer/units would tend to have lower transmissivities (T) and hydraulic conductivities (K) than the deep gravel zone. 5. pp. 16- The presentation of ground water level data in tables, hydrographs and 20 water level contour maps is complete and useful . 6. p. 21 It is unclear which wells were used to calculate a value of 2.57 feet of head difference for the K-4 cluster in June and July 1989. It appears that the head differences may be greater. For example, the difference in the ground water elevations between KS-4 and KD-4 was 4.63 feet on 26 July 1989. 7. p. 23 The report states that in general , ground water levels have declined steadily since February 1989. However, water levels have generally declined since April 1986. The drop in ground water levels has been dramatic. Specifically, ground water elevations in the western field have dropped from approximately -15.5 feet mean sea level (MSL) to -51 feet MSL between April 1986 and July 1989. This represents approxi- mately 11 feet per year of ground water decline. Previous technical reports (SNR's Groundwater Monitoring Plan, SNR's Report of Ground Water Pumping Test and Potential Contaminant Sources, and the Comprehensive Monitoring Evaluation) have clearly documented the decline in ground water levels at the site. The dynamic ground water conditions and the associated monitoring problems have been known and discussed for at least one year.