REV106751 - Laserfiche WebLink

Home Browse Search

Michael G. Attavilla Seneca Coal Company Page 8 November 24, 1993 Utilizing the equation Q=KIA and the data for 2001 presented in the table, the Division obtains the following values 1,493 gal{day and 709 gal{day fur the Wadge Overburden and Wadge Coal aquifers ,respectively. If SCC's calculations need to be modified, please check to make sure that other discussions and calculations in Tab 17 are accurate. In particulaz, please verify the discussions on pages 90 and 93, and the chemical loading calculations on pages 93 and 94. 29. On page 116 of Tab 17, SCC states that the purpose of ponds 015, O l6, and O 17 is to safely handle and treat runoff from a 100-yeaz, 24-hour storm (2.6 inches). Elsewhere in text (page 2, Tab 18), SCC states that each pond has been designed to contain and treat runoff from a 10-yeaz, 24-hour storm event. Please reconcile this discrepancy and provide revised page(s), if appropriate. 30. Maps of the II-W South area show apre-mining stock pond in t)ae drainage above and to the east of Pond 016. It appears that the pit excavation will remove this stock pond. The Division recommends that SCC consider reestablishing this stock pond at this location. Please provide a plan for replacement of the stock pond or provide an explanation if SCC does not believe reestablishment of this pond is appropriate. 31. Surface Hydrology Map 13-2A indicates that additional disturbed area runoff from the II- W South azea will flow to existing Pond 006. This additional inflow does not appeaz to be accounted for in the Pond OOb modeling. If appropriate, adjust the hydraulic input modeling information to Pond 006. 32. Drainage Basin Pond-017 azea is shown to be over 955 acres. This is a very large azea with significant runoff volume in comparison to the much smaller area of disturbance associated with the proposed year 2003 pit excavation. Has SCC considered other alternatives to treating runoff from such a large area? For example, could Pond 017 be moved closer to the disturbed pit azea outside of the Hubberson Gulch streamflow? Please consider alternatives to treating runoff from this very lazge basin, which primarily consists of undisturbed ground. 33. On page 2 of Tab 16, SCC states that increases in TDS of 41% and 255% aze possible in the overburden and the coal aquifers. The Colorado Department of Health Basic Standards for Ground Water has a maximum allowable TDS concentration of 1.25 times the background level. It appears that the estimated increases in TDS will exceed the CDOH standazd. SCC further states in Tab 17 that these increases will not have a significant impact on surface water and groundwater. With the lack of downgradient monitoring wells, How will SCC verify these conclusions? Please provide a proposed plan for monitoring the overburden and coal aquifers downgradient from the disturbed