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' i I t i A ) I . 04 March 1996 ' AGE-NC Project No 95-0144 '- Page 6 of 18 1 detected in two of the three samples at concentrations up to 0 94 mg/1 High concentrations of dissolved iron (>10 mg/l) may cause clogging of spargmg wells and soil pore space through oxidation of the iron The low concentrations of dissolved iron detected at the site should not pose the problem to system clogging TPH-g was detected in MW-1, MW-4 and MW-5 at concentrations of 490 ppm, 68 ppm and 110 ppm, respectively Water sample results (MAI Laboratory I D 61000-61002, AAL i ' Batch No 96-0131-055) are included in Appendix D a „ 5.0 QUARTERLY GROUND WATER MONITORING, FEBRUARY 11996 5 1 MONITORING WELL PURGE PROCEDURES On 08 February 1996, a Solinst water level meter was used to measure the depth to groundwater in each monitoring well relative to the top of the casing The relative ground water elevations and ' hydraulic gradient were determined from these data (Table 3) ; Following measurement of ground water depths, each well was purged of approximately 6 to 12 gallons(40 gallons for MW-8 ) of water, representing a minimum of 3 well volumes, using a 2-stage purge pump Stabilization parameters (temperature, pH and conductivity) were measured at regular intervals using a Hydac water analyzer The purge pump was decontaminated between each well ' using an Alconox solution All purged water was stored in 55-gallon drums on-site Stabilization data and field logs are included in Appendix C I 5 2 COLLECTION OF GROUND WATER SAMPLES Water samples were collected from each monitoring well using new disposable bailers Samples were transferred into 40-m1 EPA vials containing hydrochloric acid as a preservative and I-liter amber ' bottles Each sample was transported in a chilled container to MAI and analyzed for total petroleum hydrocarbons as gasoline (TPH-g), diesel (TAI-1-d), and motor ,oil (TPH-mo), and BTE&X in accordance with EPA methods 8015m and 602, respectively 5 3 RELATIVE GROUND WATER ELEVATION AND GRADIENT 1 The relative elevation of ground water in each well was calculated by subtracting the depth to water , from the surveyed casing elevation (Table 3) Ground water rose an average of 0 8I feet between November 1995 and February 1996 The approximate gradient was calculated to be,0 0060 ft/ft with a norther ly flow drr ection Ground water elevation contours are depicted in Figure 3 ' 4 I I 1