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Austin Road Landfill Appendix D Contaminant Plume Characterization Report Aquifer Test Methods coefficients can be calculated only from pumping phases based on the methods used,(Kruseman and de Ridder,1990),so columns of S do not appear for the recovery test phases. Table D-2 summarizes the K values developed from the Theis and Cooper-Jacob aquifer test methods described in the previous section. The T and K results based on time-drawdown methods are presented for each phase,including the calculated u value. Aquifer storage coefficient values are provided for the pumping test phases. To the right are the average K values for each observation well,for values that are felt to represent fair to good fit of straight-line portions and the data semi-log plots. The aquifer test results(Table D-2)show a range in estimated K from curve fits considered to be fair to good is approximately 47 to 614 feet per day(ft/d). An average K value of the shallow aquifer is using the test results for wells MW-4,MW-8,MW-9,MW-10,MW-11 and MW-14. A summary of these results from Table D-3 is as follows,based on averaged K values from the test phases considered to be fair or good. Table D-3 Summary of Average K values Well Average K(ft/d) MW-4 246 W-8 249 .9 252 M -10 288 MW-11 316 MW-14 239 These results show good consistency in the calculated K values from wells MW-4,MW-8,MW-9 with an average aquifer K value along the northern edge of the ARL of approximately 250 ft/d. The overall average K value of the shallow aquifer using all of the average values listed above is approximately 265 ft/d. It is possible that results from well MW-11 may have been affected by leakage from the stormwater runoff canal that runs from the CYA property to the detention basin east of well MW-11. Leakage from the canal would have provided a steady recharge source into the aquifer near this well. This would have reduced the drawdown associated with the aquifer testing which would have caused an increase in the calculated K value. If the aquifer test results from well MW-11 is not included,then the overall average aquifer K value for the shallow aquifer is approximately 255 ft/d. Assuming an aquifer saturated thickness of 45 feet,the average T value for the shallow aquifer is approximately 10,200fe/day. These are the aquifer T,K and b values was used in capture zone modeling described in Section 4.0. The average K value is higher than estimated by previous short-term(30 to 40 minute)tests,which showed K values to range from 108 to 182 ft/d(EMCON,1991). The K values are on the high side but within the general range based on literature values for fine to medium grained sand(Fetter,1988),which comprises the shallow aquifer layer based on borehole core samples. D-13 CDM Camp Dresser&McKee W.\REPORTS\.STOCKTOMARLPLUME.98WPPD.WPD CS 010860 City of Stockton 190855.0006