FIELD DOCUMENTS - Laserfiche WebLink

Home Browse Search

placed above the bentonite seal. The wells were completed with flush-mount, traffic-grade Christy boxes set in one foot of cement. Well construction summaries are included in Appendix B. The monitoring wells were surveyed by a licensed land surveyor of Enke and Associates, Inc., on March 22, 1996. Vertical elevations of the north edge of the top of the well casing and horizontal positions at the center of the Christy box were surveyed at each monitoring well to 0.01-foot accuracy. A static survey utilizing the Global Positioning System was performed for MW-1 and MW-3, while a conventional total station survey utilizing a nearby benchmark was performed for MW-2. A copy of the surveyor's report is included in Appendix E. 4.5 GROUNDWATER SAMPLING Groundwater samples were collected from the monitoring wells on February 29, 1996, and April 5, 1996. Prior to purging the wells, the static water levels were measured and the total depths of the wells were recorded using an electronic water level indicator. The wells were also checked for non-aqueous phase liquid using a Teflon bailer. The wells were then purged until the groundwater temperature, electrical conductivity, and pH were relatively stable; at least three well casing volumes were removed from each well using a dedicated Teflon bailer. A final water level reading was recorded once purging was complete to insure that the water column had recharged to at least 80 percent of its initial ' level. Well Purging and Sampling Data forms are included in Appendix C. Groundwater samples were collected from dedicated Teflon bailers with bottom emptying stop-cocks to reduce the loss of volatile constituents from the sample. Groundwater was transferred from the bailer into laboratory-provided 40 milliliter vials, preserved with hydrochloric acid. Three volatile organic analysis (VOA) vials were collected from each well. The samples were labeled and placed in a cooled ice chest for storage and delivery to the laboratory for analysis. The groundwater samples were analyzed for total petroleum hydrocarbons as gasoline (TPH-G) by DOHS Method; and benzene, toluene, ethyl benzene, and xylenes (BTEX) by EPA Method 8020. Proper chain-of-custody documentation was maintained on all samples. Water generated during the purging and sampling of the wells was added to the water which was previously generated as a result of the well development activities. 4.6 DECONTAMINATION PROCEDURES To prevent cross-contamination of samples, all soil sampling equipment was v decontaminated prior to, and between, sampling by washing in a non-phosphate detergent solution, then a potable water rinse, followed by a final rinse with 8