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-3- VII. Alluvial Valley Floors Information from a reconnaissance investigation (text, maps and photos) submitted to the Division to September, 1480 has documented that a 20-acre body of alluvium exists approximately 1 mile downstream from the permit area boundary. An lnstgntficant portion of the alluvial body (approximately 2 acres) is a subirrlgated Swale as evidenced by the lush grass and grass-like vegetation which contrasts with the surrounding sagebrush shrubland. The subirrlgated area 15 too small to be developed as a hay meadow, or to be managed as a unit distinct from the surrounding rangeland. As such, the valley does not qualify as an AVF on the basis of subirrigation. The applicant has documented that, while the 20-acre alluvial body does meet the geomorphic criteria of an AVF, the valley is not flood Irrigated. In order for the Division to make a negative alluvial valley floor determination, however, the applicant would have to demonstrate (by means of a regional irrigation inventory) that alluvial bodies of similar size and water availability and with similar channel characteristics are not irrigated within the region. Unless such a demonstration is made, the Division will conclude, based on available information, that the 20-acre body of alluvium extending downstream from the center of Section 16 to the county road is an alluvial valley floor. The determination 1s based on the apparent potential for flood Irrigation. At present, the AVF is undeveloped rangeland and no Impacts to the alluvial valley floor are anticipated to result from approval of the mining operation. The AVF will not be directly affected by mining disturbances, with the exception of the pre-existing access road. All coal extraction and associated surface disturbance will be over one mile upstream from the AVF. The applicant's assertion 1n the adequacy response of January 2, 1984, that no AVF exists within the permit boundary because the "bed of Grassy Creek rests on upland areas ..." 1s incorrect. As previously indicated by the Division, the reason that Upper Grassy Creek, within the permit boundary, 1s not an AVF is because the valley is narrow and steep, and the limited extent of alluvium would not be useful for either flood irrigated or subirrlgated agricultural activities. Three copies of the 7980 reconnaissance map and text must be submitted for inclusion 1n the application. If the applicant does not agree with the Division's determination, appropriate documentation regarding regional irrigation practices would have to be submitted.