2010-05-07_GENERAL DOCUMENTS - C2009087

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1. Section 2.04.5 of the permit application provides information on Grassy Creek, a perennial stream. Section 2.04.6 of the permit application provides a lithologic description of the PSCM's overburden. Section 2.05.3 of the permit application provides information regarding PSCM's depth of mining, height of mining, room and pillar dimensions, and a map of the workings. Exhibit 2.05.6 of the permit application contains a prediction of the worst possible consequences from subsidence. PSCM predicts subsidence will not occur because pillars will not be removed from the underground mine workings. Based on this detailed subsurface information, the Division finds that PSCM's proposed undermining of Grassy Creek stream will not cause material damage to the stream. (4.20.4). XIII. Operations on Alluvial Valley Floors Section 2.06.8 of the permit application contains information on alluvial valley floors (AVFs). The following three AVFs are within the area of influence of the PSCM: the Fish Creek AVF, the Grassy Creek AVF, and the Little Grassy Creek AVF. The Fish Creek AVF extends the length of Fish Creek to its confluence with Trout Creek. The Grassy Creek AVF is a 45-acre area near the Grassy Creek/Little Grassy Creek confluence. The Little Grassy Creek AVF is a 40-acre area that extends along a narrow strip on both sides of Little Grassy Creek upstream from the Little Grassy/Grassy Creek confluence. The Division previously determined that Cow Camp Creek, an ephemeral tributary of Fish Creek, is not an AVF based on severely limited farmable acreage due to the meandering nature of the stream channel. The Division affirms its previous AVF determination for the Fish Creek AVF that is documented in the findings documents of the Foidel Creek Maine (C-82-056). Alluvial deposits on Fish Creek meet alluvial valley floor criteria based on existing flood irrigation, potential for flood irrigation and subirrigation. The existence of a currently flood-irrigated field on lower Fish Creek and the presence of diversion structures and irrigation ditches on various stream segments as delineated on Map 15 in the Foidel Creek Mine permit application document the potential for flood irrigation. Alluvial soil types in the Fish Creek drainage exhibit late growing season ground water elevations within 6 feet of the surface (Foidel Creek Mine permit: Exhibit 16 - Soil Mapping Unit Descriptions, and backhoe pit data, page 2.06 -9). Hay crop species commonly grown in the Yampa Basin would be expected to derive benefit from ,ground water when present at such shallow depths. The major vegetation type on the Fish Creek AVF within the permit area is a sagebrush meadow community dominated by silver sagebrush with a number of sedge and rush species contributing significantly to the community. All of these species are hydrophytes typically associated with subirrigated conditions. In connection with a review of the Foidel Creek Mine permit application, the Division received a letter from one of the surface owners in the Fish Creek drainage, Mr. Edward Camilletti, dated January 23, 1998. The letter estimates 1% of the production of the Peabody Sage Creek Mine 35 May 7, 2010