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i • • • Summarize the results of the new analyses and groundwater level depth measurements in a report for submission to ABF and the SJCo PHS/EHD, which is the purpose of this letter report • Abandon the three monitoring wells in accordance with county and state well standards after the results of the new groundwater samples have been reviewed by SJCo PHS/EHD and receiving approval from ABF METHODS OF GROUNDWATER SAMPLING AND WATER LEVEL MEASUREMENT The field investigation was conducted on March 19, 1999 and consisted of groundwater depth measurements and collection of groundwater samples The depth to the groundwater table was measured in each of the three monitoring wells with a Solmst electronic sounding tape measure prior to purging and sampling the wells The measurements were taken from the top of the PVC casing at a mark placed there earlier by Moroe Surveying, or on the north side of the collar Measurements were taken to the nearest 0 01 foot and recorded on a Water Level Monitoring Record (attached) Water table relative elevations are summarized in Table 3 below Prior to collecting groundwater samples, groundwater was purged from the three wells with new, dedicated, disposable, one-liter capacity, polyethylene bailers The recovered groundwater was very cloudy with high silt concentration There was no perceptible change in the degree of siltiness, even after removing 7 9 well casing volumes of groundwater from monitoring well MW-1 (8 4 liters of water per well volume) The water was medium rusty orange-brown, but had no odor A total of 4 5 well volumes of groundwater was purged from each of the monitoring wells MW-2 and MW-3 The groundwater in those two wells remained equally silty as that in MW-1 Purged groundwater was poured into a 55-gallon metal drum for temporary storage The metal lid to the drum was secured with a bolt-down ring A label . was affixed to the drum indicating it contained monitoring well purge water The wells quickly recharged with groundwater The water levels after purging were only 0 03 to 0 04 foot lower than before The temperature, pH and conductivity were measured in samples of groundwater at the start of, during, and completion of purging The measurements were recorded along with other data on Monitoring Well Sampling Record and Well Development Data sheets (attached) and are summarized in Table 4 below The measurements, in theory, should help determine if representative groundwater had entered into the well from the surrounding formations after sufficient purging It is interesting to note that the temperature of the groundwater increased by up to 5° F after purging However, the pH and conductivity changed little Table 4 Monitoring well data prior to groundwater sample collection on March 19, 1999 MW No. Water Table No Well Start/Finish of Purging Relative Vols Temp pH Conductivity Elevation(ft)* Purged (°F) (pH units) (�tS/cm) MW-1 1362 79 61 6/643 728/7/74 9 5/11 4 MW-2 1 13 58 45 61 2/659 7 80/7 90 32/2 1 MW-3 1 13 58 1 45 1 64 8/70 4 795/795 0 8/0 8 *Note Elevations are relative to that of a temporary bench mark Groundwater samples were collected with the same dedicated disposable bailers used to purge the respective wells Samples to be analyzed for TPH-D were transferred from the bailers to 1 liter, amber glass bottles with Teflon lids Preservative was not added to these samples Samples for BETX and MTBE analyses were transferred to specially designed 20 ml glass vials pre-charged with hydrochloric acid preservative The vials were carefully filled to ensure no air bubbles were entrained in the sample