2010-12-08_PERMIT FILE - C1981008A (19)

Home Browse Search

root structures to a depth of greater that 10 feet depth. A single discontinuous layer of broken angular rock about six to twelve itches thick is present within much of the observed cut face. This is the only empetent rock in the bench I cut face. 'Fhe bench 1 material overlies competent overburden, which overlies the coal seams that are mined (sec Photo 1). Bench !material is mechanically removed as a separate unit and is the last overburden unit to he placed over the reclaimed mina As such there are generally several or more feet of the bench 1 material underlying replaced topsoil in the reclaimed areas. Part of the area of the mine south of BB Road and west of 2 ?00 Road (reclassified as prime farmland) and part of the area north of BB Road (ion -prime farmland) have been rained and have had overburden placed, but have not had topsoil replaced (Figure 1). The suitability of the Bench 1 subsoil for use as the lower layer of prime farmland soil is the focus of this study. Preliminary In vestigation On January 31, 2008, WFC personnel obtained six soil samples from the upper two feet of overburden (samples 101 through 106, Figure 1). The soil was analyzed for texture, conductivity, pH, nitrogen, organic matter, some anions and cations, calcium carbonate, moisture, and sodium adsorption ratio. A summary of'results relevant to prime farmhand soil is presented in "Fable 1 and the tab data sheet is attached to this letter. These samples were all within suitability criteria established in the permit and by the NRCS for prime farmland subsoil for target analytes with the exception of one sample which exceeded the electrical conductivity (soluble salts) suitability standard of 4.0 with a reading of 4.1 micromhos /cm. Second Investigation After a meeting with the f+RMS, NRCS, WFC, and other personnel, WFC agreed to further analyze the condition of the subsoil by examining the soil in pits placed on a 2.5 -acre grid (330 feet per side). These grid points were seduentiaily numbered across the portion of the mine that had been mined and partially reclaimed. Of the 34 grid points, twenty were within areas that had been brought to grade with ovefburden and were accessible (c.g. not covered with topsoil pilcs). These locations had soil pits excavated, with 13 south of BB Road (in prime hrmIland) and seven north of BB Road (in non -prime farmland) (sample points numbered 1 th -rough 34, Figure 1). All pits were excavated in areas that had been brought to grade with overburden, but had not been prepared for topsoil placernerr, or had topsoil placed. WFC dug pits using a baekhoe to a depth of three, to four feet Walsh personnel visited tae site on March 5, 2008 and described soil color, texture, percent coarse fraction (gravel, cobbles, stones, and boulders), and hardness. Information was recorded into afield notebook and transferred to Table 2. No boulders (>25 inches) were observed in any soil pit. Soil samples were obtained from the upper two feet of the exposed soil. Samples from the prime farmland area and select samples from the non -prime fannland area were send to Servi -Tech Laboratories of Hastings, Nebraska for pit, texture, calcium carbonate, and exchangeable sodium percentage (BSP) and other analyses. Laboratory results are summarized in Table 2. Selected lab analyses were based on discussions with David Deastyne of the NRCS Montrose office. Mr. Dearstyne stated in an email dated February 20, 2008 that soil deeper than 24 inches in prime farmland should be tested for those parameters and compared to standards (shown on Table 2). If the soil is within these criteria it would provide suitable subsoil (copy of email correspondence is attached). Endo,nmcntal Su ;ntists end Engineers, LLC Revised September 2010 (PR 06) Attachment 2.05.4(2)(d) -1 -3