ARCHIVED REPORTS_XR0007344 CASE 2

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the USC system of soil classification as each of the borings was advanced in depth The boring logs, showing the lithologies encountered, are presented as Figures 4 through 8 Copies of the original field logs are included in Appendix B The three groundwater monitoring wells are constructed of four-inch (4") diameter, flush couple, schedule 40 PVC casing with twenty feet (20') of 0 02 slot screens and a screw cap at the base (see Figures 9 through 11) The annular space between the casing and the boring wall was packed with Lapis Luster#I C sand to a level two feet above the top of the screened interval This sand was chosen to best match the slot size of the well screens On top of the sand pack, a three-foot layer of bentonite pellets was placed, densely packed and hydrated to provide a firm seal to the well screen All depths and thickness of sand pack and bentonite seals were verified I by sounding with a weighted tape The remaining annular space was back filled with a neat cement grout up to the ground surface In the two borings that were not converted to monitoring wells the entire boring was tremmied up to the ground surface with neat cement grout as the sections of drilling pipe were extracted Surface completions of all wells extend approximately three feet above surface grade The top of each well casing has been equipped with a PVC slip cap and enclosed in a 10-inch steel monument pipe with a lockable Ind Each monument is surrounded by a 3-foot by 3-foot square concrete pad and steel bollard posts to identify and protect the wells A state licensed surveyor surveyed the elevations of each of the wellheads on October 29, 2002 The results of that survey are included in Table 2 and the survey information was used in this report to derive a preliminary determination of the water table flow gradient map (Figure 3) SOIL,AND PRELIMINARY GROUNDWATER SAMPLING Soil samples were collected for chemical analysis from each soil boring, starting within the first ten feet of the surface and then at variable intervals until the boring penetrated the I groundwater table Sampling intervals beyond the initial 10 feet were based on observing major changes in the lithologic color or composition of the cuttings or whenever any marked increases in organic vapor concentration were detected by the use of a Foxboro organic vapor analyzer (OVA, Model 88) Soil samples were collected into a laboratory supplied, precleaned, 4-ozjar Each jar was filled and then leveled off even with the rim to minimize air space and to screw on the jar cap The sample far was labeled, and then immediately placed into a cool icechest for ' subsequent laboratory analysis at the Severn Trent Laboratory (STL) facility in Pleasanton, CA Upon reaching the water table (-124 feet bsg) a groundwater sample was withdrawn ' from each bonng with a pre-cleaned, Teflon, hand bailer A fresh length of retention chord was attached to the bailer at the start of sampling in each boring The bailer was repeatedly lowered down the center drill pipe to extract enough groundwater to fill two laboratory supplied, one- liter, amber glass sample bottles Each of the sample bottles were properly labeled and placed into a cool rcechest After each sampling sequence the retention chord was removed from the hand bailer, discarded and the bailer was properly re-cleaned and readied for the next boring I 1