REP47405 - Laserfiche WebLink

Home Browse Search

HYDROLOGY IMPACTS 1987 GROUNDWATER - EXISTING MONITORING AND IMPACTS Page -2- ~~ precipitation. Because the amounts of precipitation vary from year to year, [he water levels are also expected to change. The OVWM terrace piezometer also shows change attributable to precipitation re- charge to the water table under the fill. The water level rose to 52' 6" in June, 1987, and steadily decreased to a level of 62' 2" in November, 1987. Mon- itoring during the firs[ few months of 1988 shows a steady rise in the water level consistent with the first data obtained from the well in 1987. Bedrock Groundwater: Depth to groundwater was measured in six monitoring wells in 1987, including DH-58, DH-60, DH-65, DH-69, DH-70 and GR77-7. The sampling tube of DH-70•-c5a~s i.noperab,~.e so' no quality measurements could be obtained. One-Isamp"1e from GR,77.,)E was obata~ined`before the' we11~ becafie c'1'ogg`e8"with"Z'ihat was believed to be, a d,e- c,ayimg ¢odent. The sampling tube was pulled from the well in October, 1987, and was found to be filled and covered with a rotting material. The well would need to be flushed and the sampling equipment cleaned before additional data could be obtained. Data obtained prior to the removal of the sampling system were con- sistent with past years. DH-58 continued to be dry. DH-60, DH-65, DH-69 and DH-70 showed little varia- tion in past patterns of water levels. Levels changed in some wells up to 15 feet. Evidence of recharge Erom surface or colluvial-alluvial waters is shown • in the rise in the water level from 503 feet to 489 feet in DH-70, for example, from December, 1986, to June, 1987. Levels then consistently dropped through the remainder of 1987, and are expected to have risen again in the first part of 1988. ORCHARD VALLEY MINE SITE WATER MONITORING AND IMPACTS Surface runoff from the Orchard Valley and Orchard Valley West Mines is con- tained within nine sedimentation ponds. During 1987 these ponds contained only small amounts after snowmelt, runoff, and precipitation events. For the most part, the ponds remained dry. As a result, sedimen~'i'levels remained low and none required cleaning. Only the stockpile pond was pumped (2,000 gal.) early in the year. Any discharges required were in compliance with NPDES Permit No. CO-0033685. Groundwater data from Boreholes B-1 through B-8 and MW-1 remained consistent with past years. Boreholes B-1, B-5 and B-6 remained dry. Borehole B-2 is lo- cated in the Orchard Valley Mine diversion ditch and contains water during peri- ods of high runoff. The water level steadily decreased until the hole was dry in December, 1987. Water levels in Boreholes B-3 and B-4 and Monitoring Weli MW-1 gradually declined through the year, as was expected. Quality and water level data for Node 22 (Borehole B-7) remained similiar to past years. The water level steadily decreased through the year as was expected.