ARCHIVED REPORTS XR0000065 - Laserfiche WebLink

Home Browse Search

Mr Martin Harms April 18, 2001 Page 3 of 6 2.3 Well Construction Based on the lithology and the depth to groundwater (7-9 feet bgs) encountered during drilling, wells MW 1 through MW4 were screened from approximately 5 feet bgs to 20 feet bgs The wells were constructed of 2-inch diameter, Schedule 40 PVC casing and screen (0 010-inch slots) The filter pack consisted of 17 feet of 2112 silica sand The annular seal contained 2 feet of bentonite overlain by concrete, which was approved on site by Lon Duncan of PHS/EHD The wells were completed at the ground surface by traffic-rated, flush-mount well boxes Bonng/well construction logs are included in Attachment A 24 Well Development and Groundwater Sampling On January 23, 2001, a Ground Zero technician surveyed the well casing elevations, developed the new wells, and collected groundwater samples Water levels were monitored prior to well development An experienced Ground Zero technician developed the new wells by surging, bailing and pumping each well until turbidity was minimized During the well development process, temperature, pH, and electrical conductivity were measured and allowed to stabilize prior to collecting a . groundwater sample Groundwater purged from the wells was placed into labeled DOT approved 55-gallon drums, which are currently stored on site pending disposal Groundwater samples were collected from each well after physical parameters had stabilized and the water in the well had recovered to at least 80% of pre-purge levels Samples were placed in an ice chest at a temperature of 4° Centigrade and submitted to Argon Laboratory under chain of custody protocol The samples were analyzed for the presence of TPHg by EPA method 8015, BTEX by EPA method 8020, and oxygenated gasoline additives, ethylene dibromide (EDB), and 1,2- dichloroethane (1,2-DCA) by EPA method 8260 Field development/purge logs are included in Attachment B 30 RESULTS 3.1 Subsurface Conditions Shallow soil beneath the site consists of well graded sand from the ground surface to approximately 9.15 feet bgs This laterally continuous sand unit is underlain primarily by fine grained silts and clays to a depth of at least 21 feet bgs, although clayey sand was encountered in borings SB 1 and SB2 (located just north of the former UST) to a depth of approximately 23 feet bgs, and well graded sand was encountered in boring SB2 from approximately 23 feet bgs to 26 feet bgs No monitoring well was completed deeper than 20 feet bgs Slight to moderate petroleum hydrocarbon odors and soil discoloration were noted in soil samples collected at depths of 5 and 10 feet bgs from boring MW 1, but no odors or discoloration were G 1Dita1GROUNDZE1TuPfBoylReports\WELLRPT doe