REP47405 - Laserfiche WebLink

Home Browse Search

HYDROLOGY IMPACTS 1987 GROUNDWATER - EXISTING MONITORING AND IMPACTS Near Surface Colluvial-Alluvial Groundwater: CWI continued to monitor 29 springs within the permit area during 1987. These included Spring Nos. 16 through 25; 28 through 31; 1-3 and 1-5; 5-1; 6-4 and 6-6; 7-1, 7-4, 7-5, 7-9 and 7-10; 8-S; .12-4; 13-5 and 13-6; and 24-1 (see Map 4-1 ). Of these resources, Spring Nos. 7-1, 7-4, 7-5, 23, 24 and 24-1 were either undermined or are adjacent to developed areas of the Orchard Valley Mine. No springs have been undermined by the Orchard Valley West Mine. One spring not included in the monitoring program is located adjacent to the OVWM development. No impact to this spring is anticipated as overburden depth is greater than 500 feet. Statistical calculations of field electroconductivity, field pH, calcium, mag- nesium, sodium, sulfate and total dissolved solids were completed on representa- tive springs, i.e. spring Nos. 16, 17, 19, 20, 22, 23 through 25, 29, 30, 7-5, 13-5 and 13-6. Statistical calculations of flow were completed on spring Nos. 16, 17, 20, 22, 23, 25 and 30. Minimums, means and maximums of the parameters are presented graphically and follow the 1987 data charts Eor these resources. Generally, flows were affected by the amount of precipitation and subsequent percolation and runoff in a given year. The maximum flows of the springs were usually recorded during the Spring runoff and were diluted largely by surface flows. Low flows of springs of a colluvial nature were usually recorded during • late Fall and varied depending on the amounts of precipitation earlier in the year which had percolated into the colluviam/alluvium. Flows of all springs within the permit area are relatively small, rarely exceed- ing 1.0 cfs, even during periods of high runoff. Variations in flows exhibited in the data and graph are usually 1/100th or 1/1,000th of a cfs. The flow graphs show the same basic pattern of mean flow. Most springs show increases or decreases in the mean flow during the same year, i.e. in i985, most springs showed slightly larger flows and in 1986, most springs showed a lower flow. This may be due to levels of precipitation in the earlier part of the year. Graphs of the physical and chemical parameters also showed typical patterns rel- ative to the amount of precipitation and runoff. In those springs of a colluvi- al source, the minimum, mean and maximum levels of sulfate, calcium, magnesium and sodium were generally the same as the total dissolved solids and were af- fected by dilution of precipitation and runoff. No affect from mining has been evidenced. Changes in flows and chemical charac- teristics can be attributed to levels of precipitation. Most resources overlie the workings or mineable seams by more than 500 feet. Many are in areas of 1,000 feet or more of overburden and no impacts due to mining are anticipated. CWI monitored eleven shallow monitoring wells during 1987. These are Well Nos. SM-1 through SM-11. A piezometer well in the south terrace of the OVWM mine bench was also monitored. Chemical characteristics were again consistent with • past years. Levels varied only a few feet. Levels in SM-10 and SM-11 north of the OVWM site changed a few inches, as these wells are within the water table recharged by East Roatcap Greek. The ~watec level in SM-5 {Located. more than 1.,000'~or th ,t~ q£afie South 'III' Sub-Mains, `dropped~a~ Co"tah off 15 feet from Matey +tt'"~i©c o[~'^b~r~`, 9$7. The water level had dropped in past years but cannot be com- pared as data was not obtained for the same number of months of the year. As is evidenced by the last Level reading in 1986 (16' 3"), and the first level read- ing in 1987 (8' 4"), the colluvial aquifer in the area of SM-S is recharged by