2018-01-03_REVISION - C1994082 (29)

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alluvial valley floors exist in the permit area or the adjacent Grassy Creek watershed which are in hydrologic communication with the Yoast Mine. As a result of 1990 AVF investigations in the Sage Creek watershed, Seneca Property, LLC concluded there are no AVFs in this basin in hydrologic communication with the Yoast Mine. Based on information submitted by the applicant; field reconnaissance; interviews with farmers; and previous findings by the Division and the applicant related to the Seneca II -West Mine, the Division previously did not concur with the applicant's conclusion. The Division concluded that two areas along Sage Creek downstream from the Yoast permit met the regulatory definition of alluvial valley floors. These areas are discussed below. Sage Creek Reservoir Site Two fields located just upstream from the former Sage Creek Reservoir dam (Sections 13 and 18) are identified in the Yoast application as sub -irrigated native wetlands and sub -irrigated grass hay fields. The native wetland area is basically the area once covered by the reservoir, which failed in 1985. This area is currently used for grazing. The area immediately upstream from the former reservoir site is currently used as a grass hay field. These fields are located in the upper reaches of Sage Creek, and therefore are not typical of alluvial valley floors in this area with agricultural potential. However, the upper field (approximately 10 acres) is currently being farmed for hay, and the other larger field appears to have the potential to be put to use as a sub -irrigated hay field. Furthermore, during a site visit on May 19, 1995, the upper grass hay field was being flood irrigated by means of an irrigation ditch along the eastern edge of the field. This was confirmed during the review of Permit Revision No. 1 (PR -1). Due to the existence of flood irrigation and the presence of sub -irrigation of the unconsolidated streamlaid deposits in the fields immediately upstream from the old Sage Creek Reservoir, these fields are determined to be alluvial valley floors. The field just above the breached Sage Creek dam is dissected by the streambed. This area is undeveloped rangeland that is currently used for grazing. The limited size of the field would make it difficult for farm equipment to operate. This field is not typical of agriculturally productive alluvial valley floors in this region. However, the upper field in Section 18, T5N R88W, is currently being farmed for hay. The creek was diverted from the center to the perimeter of the field and the creek bed was filled to create a manageable flood irrigated field. The field is ten acres and is flood irrigated during high flow. The family that manages the field does not have adjudicated water rights for the surface water in Sage Creek. They have an agreement for early runoff withdrawals, allowing limited flood irrigation until mid-June when stream flows decline to a level precluding further withdrawals. It is unlikely the field will be irrigated with water at the projected worst-case salinity levels, but Seneca Property did provide an estimate of what the potential worst-case impacts to the agricultural operation would 34