Laserfiche WebLink
PSCM's mining during the initial permit term: Scotchman's Gulch, Annand Draw, and <br />Grassy and Little Grassy Creeks upstream from their previously determined AVFs. Of <br />these stream segments, only Scotchman's Gulch near its confluence with Grassy Creek <br />appears to have the geomorphic characteristics of an AVF (unconsolidated stream -laid <br />deposits holding streams). Annand Draw and the upper reaches of Scotchman's Gulch <br />lack unconsolidated stream -laid deposits sufficient to hold a stream, and therefore these <br />stream segments do not meet the criteria of an AVF. Grassy Creek and Little Grassy <br />Creek, upstream from their two previously determined AVFs, lack farmable acreage <br />next to their channels as a result of the channels' incisement into bedrock; therefore, <br />these upper reaches of Grassy and Little Grassy Creeks are determined to not be AVFs. <br />Although Scotchman's Gulch has unconsolidated stream -laid deposits sufficient to hold <br />a stream, the Gulch does not meet the criteria of an AVF based on insufficient water for <br />irrigation use and lack of subirrigation characteristics, as documented in Exhibit 2.06.8- <br />Elof the PAP; therefore, Scotchman's Gulch near its confluence with Grassy Creek is <br />determined to not be an AVF. <br />Surface coal mining and reclamation operations will be conducted to preserve the <br />essential hydrologic functions of alluvial valley floors outside the permit area and to <br />reestablish the essential hydrologic functions of alluvial valley floors within the <br />affected area throughout the mining and reclamation process (4.24.2). <br />Effect of Mininiz on Identified Alluvial Valley Floors <br />The PSCM will discharge mine disturbance runoff, coal spoil leachate, and <br />underground mine water into the stream channel in the Grassy Creek AVF via pond <br />002, and into the stream channel in the Fish Creek AVF via pond 004. The runoff and <br />leachate can be expected to be alkaline, with the chemical constituents of greatest <br />concern being dissolved solids, mainly salts of sulfate. PSCM proposes no new <br />disturbances or discharges in the Little Grassy Creek AVF; therefore, there is no <br />potential for material damage to this AVF. <br />No changes are proposed for the Pond 004 watershed during PSCM mining; therefore, <br />the Division's evaluation of that watershed as described in the findings document for <br />the Seneca II Mine is applicable to the PSCM mine. Pond 004 is part of the current <br />SL4 bond release application, under consideration by the Division. Table 2.05.6(3)-T1 <br />of PSCM permit application contains a mass balance analysis that indicates that mixing <br />of discharges from PSCM ponds with stream waters will result in maximum TDS of <br />3,259 mg/l in the channel of the Grassy Creek AVF. Although 3,259 mg/l equates to <br />4,345 mmhos/cm, a value well above the 1,000 mmhos/cm material damage threshold, <br />the high TDS is a result of Seneca II surface mining activities that, as previously <br />explained, are exempt from AVF material damage rules 3.06.8(5)(a)(i) and (ii). Based <br />on the limited effects of PSCM discharges from underground mining activities on <br />surface water quality in the Fish Creek, Grassy Creek, and Little Grassy Creek AVFs, <br />alluvial ground water quality should not be significantly impaired. Subirrigation is <br />expected to be less affected by mine discharge than by irrigation using surface waters. <br />24 <br />