SITE INFORMATION AND CORRESPONDENCE

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7uJOuo_. J" 1„uli-.Jl 4.3.2.3.5 Davis and De Wiest (1966) list water with greater than 500 mg/l of bicarbonate alkalinity as being poor quality water for irrigation. As shown in Table 4.3-2, the bicarbonate concentrations range between 144 and 290 mg/1 , indicating that bicarbonate alkalinity would not be a significant factor to impair irrigation water use. 4.3.2.3.6 One further measure of the suitability of groundwater for irrigation is the sodium adsorption ratio (SAR) . Using the results of the three groundwater samples, the adjusted SAR (Rhodes 1972) was calculated. These SAR results are 4.3 for groundwater from Well LM 60, 4.5 for LM 56, and 6.1 for groundwater from LM 72. All three values fall within the "low" category indicating that, with regard to the SAR, the groundwater can be used with little danger. 4.3.2.3.7 In summary, while alkalinity and SAR do not appear to be of concern, the concentrations of boron and salinity may limit the use of groundwater from the Upper Tulare HSU north of the Depot for irrigation purposes. 4.3.3 Private Well Sampling 4.3.3.1 As discussed in Section 2.5.2, 15 private groundwater wells were sampled within a 1-mile radius of the Depot. Of these 15 locations, nine wells are considered to be either upgradient or cross-gradient of the site. The chemical results of groundwater from these nine wells were used to further characterize the range of natural groundwater quality (see Section 4.3. 1 for discussion) . The remaining six wells (LM 1, 6, 7, 11, 12, 13) shown on Figure 2.6-1 are located generally north or northeast and generally downgradient of the facility. The analytical results of all 15 private wells samples for both the organic and inorganic parameters tested are summarized in Tables 4.0-22 and 4.0-23. The laboratory data sheets of the sampling can be found in Draft Letter Report, Task 8 -- Sampling and Analysis of Private Wells, Defense Depot Tracy, California, dated March 19, 1987. 4-165