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IMr Michael lnfuma Page 3 of 6 2.3 Well Construction i Based on stratigraphy, current depth to groundwater measurements and historical depth to groundwater measurements, wells MW5 through MW7 were screened from 55 to 75 feet bgs and well MWID was screened from 95 to 100 feet bgs The wells were constructed of 2-inch diameter, Schedule 40 PVC Icasing and 0 020 inch slotted screen The filter pack consisted of 43 silica sand The annular seal contained 2 feet of bentomte overlain by neat cement grout to the ground surface Well construction logs are included in Attachment A 2.4 Well Development and Quarterly Groundwater Sampling On November 26, 2003, water levels in wells MWID, and MW5 through MW7 were monitored prior to planned development activities Depth to water ranged from 56 37 feet below the top of the well casing (btoc) in well MW7 to 57 00 btoc in well MWID Well MW5 was developed by surging pumping and bailing until turbidity was minimized Pump failure precluded development of the other wells Well development logs are included in Attachment B Water levels in all site wells were monitored on December 8, 2003 prior to the development of wells MWID, MW6 and MW7 Depth to groundwater in the shallow A zone wells (MW1 through I MW4) ranged from 56 38 feet btoc to 57 13 btoc Depth to groundwater in the intermediate B zone wells (MW5 through MW7) ranged from 55 38 feet btoc to 55 83 btoc Depth to groundwater in C zone well MWID was 57 47 btoc Water level data are summarized in Table 1 Field data sheets lie are included in Attachment B Groundwater elevation was determined in each well by subtracting the surveyed wellhead elevation from the respective depth to groundwater measurement Based upon the observation at the adjacent U- Haul site that potentiometic surface elevation and groundwater flow varies with completion depth, the wells at the site have informally been divided into three zones of completion a shallow or "A Zone" I represented by wells MWI, MW2, MW3 and MW4, an intermediate zone "B Zone" represented by wells MW5, MW6 and MW7, and a deeper "C Zone" (MWID) On December 8, the potentiometric surface of the A Zone wells ranged from 37 65 feet to 37 70 feet below mean sea level (MSL) The potentiometnc surface of the B Zone wells ranged from 37 65 feet to 37 67 feet below MSL The potentiometric surface in C Zone well MW 1 D was 38 01 feet below MSL The average hydraulic gradients in both the A and B zones were less than 0 001 ft/ft Potentiometnc surface maps for the A I and B Zones are depicted on Figures 2 and 3, respectively The elevation of well MWID is shown on Figure 2 I On December 8 and 9, new wells MWID, MW6 and MW7 were developed by surging pumping and bailing until turbidity was minimized The other wells were purged of at least three casing volumes prior to sampling Physical parameters (temperature, pH, electrical conductivity and turbidity were measured during the development of wells MWID, MW6 and MW7 and purging of wells MWI through MW5 Groundwater samples were collected after the physical parameters had stabilized, and the water level in each respective well recovered to at least 80% of its pre-purged level The samples were submitted to Argon under chain of custody protocol for the analysis of BTEX by EPA method 8021B, TPHg by EPA method 8015B and gasoline additives by EPA method 8260B Well development and purge logs are included in Attachment B I11GZA_FSIVOL_IIDATAIGROUNDZE\RARRYS\Reports\Well Report2 doc