2001-07-02_GENERAL DOCUMENTS - M1974052

Home Browse Search

Mr.Roger Doak Coal Ash Pilot Project Proposal June 26,2000 Page 3 For comparison purposes there were 5 of 108 leachate analyses that exceeded standards which could not be attributed to background levels. Samples from four pond samples exceeded standards in 8 of 108 analyses. The pond water exceeded the sulfate standard for all samples submitted and for iron, lead, manganese and nitrate in one sample for each parameter. Boron was detected in column samples at concentrations ranging between 1.3 and 4.1 mg/L. Varra Companies owns the property on which the proposed pilot project will occur and does not utilize groundwater for crop watering. As such the standard of 5.0 mg/I for boron should apply. Boron concentrations in water samples obtained from the Varra property varied between 0.21and 0.66 mg/L. Molybdenum was detected in column leaching samples at concentrations varying between 0.11 and 0.47 mg/L. The highest concentration was detected in samples obtained from the first pore volume. Molybdenosis in cattle has been observed where molybdenum concentrations in groundwater exceeded 5 mg/L. It is reported that typical human diets contain molybdenum at 100-1,000 µg per day. It is recommended that consumption of molybdenum should not exceed 0.50 mg per day (NAS 1977). The average concentration of molybdenum observed in the column experiment are an order of magnitude below the levels required to cause adverse health affects in farm animals or humans. The column leaching samples represent the point where water intersects the ash in the trench. A three dimensional,steady state analytical model was used to estimate the concentration of boron and selenium at various locations downgradient of the proposed trench. The average concentration of the four pore volume analyses was used as the source concentration. In the case of selenium the method detection limit value was used in the average when concentrations were below the reporting limit. Concentrations were estimated at distances of 50 and 200 feet as the state will require that sentinel wells (also known as action wells)be installed 50 feet downgradient of the trench and the closest property boundary to the proposed trench is roughly 200 feet. The calculated values for boron and selenium at the respective distances are 0.620 and 0.221 and .004 and .001 mg/L, respectively. The model values should be conservative, as they do not account for retardation or water-rock interactions that may occur. Model data indicate that adverse impact to off-site properties will not occur. Model results are presented in Attachment B. Comments regarding your response to the CD submittal are presented below. I. We do not believe water rights are an issue for this or any proposed project. A large scale reclamation would dramatically reduce consumptive groundwater losses. Concerns regarding the affects of the proposed pilot trench on groundwater flow at the study area were evaluated by use of a two-dimensional analytical groundwater Flow model (TWODAN) and by analytical solutions provided by Harr (1962). The model was used to simulate groundwater flow conditions with the proposed trench in place. TWODAN is a 32-bit Windows program for the modeling of two-dimensional groundwater. The program is accepted by scientific community for evaluating two dimensional groundwater flow problems and was evaluated in Groundwater, v. 36, No. 3, May-June 1998. A uniform flow field was defined in the model with an unconfined aquifer. The hydraulic conductivity of the aquifer was estimated at 100 to 150 feet per day (the model used 125 feet per day). The aquifer thickness is about 20 feet. A 100-foot long trench was placed in the uniform Flow field and a plot was generated showing the water table contours and flow path