GENERAL32564 - Laserfiche WebLink

Home Browse Search

SENECA [I MINE REGRADED SPOIL MONITORING PLAN REVIEW Wolf Creek Mininq and Reclamation Area Peabody has completed an evaluation of the regraded spoil monitoring program that is used to determine spoil suitability in the Wolf Creek reclamation area at Seneca II Mine. The fallowing text summarizes this evaluation and discusses two proposed revisions to the existing plan. Spoil samples have been collected from the Wolf Creek mining and reclamation area since 1984. The data has been evaluated, summarized, and submitted to CMLRD in three annual monitoring reports (1986, 1987, and 1988 field seasons) and the response to comments for the Permit Renewal Application (10/14/86). Data from the 1989 field season will be submitted to CMLRD in April 1990 as part of the Fourth Annual Topsoil and Spoil Monitoring Report. Samples have been collected on a 300 foot grid and at representative revegetation monitoring sites. The existing parameter list for sampling regraded spoil in the Wolf Creek reclamation area was based upon the information acquired during the premine overburden assessment. The approved parameter list for Seneca II Mine, described on page 9-40 of Tab 9 and pages 6-153 and 6-164 of Tab 6 in the PAP, includes soil reaction (pH), soil salinity (EC), acid base potential (ABP), and extractable manganese (Mn). A sufficient number of spoil samples have been collected from the 1983 through 1989 reclamation blocks to determine spoil characteristics, compare spoil quality to premine overburden quality, and ascertain the degree of sample variability. The data is summarized and discussed in three separate categories; mixed spoil, selectively handled spoil topdressing, and premine overburden (see Table 1). Salinity. Mean salinity values for the selectively handled spoil topdressing, mixed spoil, and premine overburden are 2.0, 3.3, and 1.9 mmhos/cm, respectively. Salinity values ranged from 0.3 to 3.7 mmhos/cm in the spoil topdressing, from 0.3 to 11.5 mmhos/cm in the mixed spoil, and from 0.1 to 5.9 mmhos/cm in the premine overburden. Mean annual salinity values showed little variation from 1984 ,t~irough 1989 (Table 1). Two salinity values in the mixed spoil wer-e-in_e~cCE$~ance-of• the maximum allowable level of 8.0 mmhos/cm for suitable material (Seneca II Mine PAP, Tab 6, Table 6-3). These two samples were also extremely acidic with pH values of 2.3 and 2.5 and ABP deficiencies of 29 and 48 tons of calcium carbonate per 1000 tons of material. Overall, the salinity levels are low to moderate in the 1983 through 1989 reclamation blocks and should pose no severe problem to successful reclamation. Salinity levels in the upper four feet of regraded spoil are slightly, but not significantly higher than premine values. Only two percent of the total spoil samples had salinity values greater than five mmhos/cm. These three samples also had extremely unsuitable reaction values of 2.3, 2.5, and 3.3. The excess acidity and salinity is attributable to the oxidation of reactable iron sulfide minerals (framboidal and microcrystalline forms of pyrite and marcasite) to sulfate salts.