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1 <br /> <br />' Adjoining uses include irrigated lands on part of the east <br />' side as well as the south, west and north sides. Farmhouses <br />and yards are located on the southeast and south side. Two sand <br />' and gravel mining operations adjoin on the east side. <br />Geologic Setting. Mining will be from the Piney Creek alluvium <br />on the St. Vrain Creek drainage. The eastward dipping beds of <br />Upper Cretaceous age are overlain at an angular unconformity <br />1 by the Piney Creek alluvium. This area is on the west side of <br />' the asymetric D-J Basin. The sand and gravel encountered in <br />the Piney Creek alluvium are a result of water erosion and redeposi- <br />tion of rock materials from the front range of the Rocky Mountains. <br />The deposition of this alluvium occurred during a time when <br />' the creek was a good deal larger than it is now. But, judging <br />from the scarcity of large rocks found at the location, the velocity <br />of the creek must have slowed sufficiently to have dropped boulders <br />' and most of the large cobbles before it reached this point. <br />There does appear to be more than enough medium and small cobble <br />' to make this a good aggregate source. <br />' Nearby mining operations, both upcreek and downcreek, indicate <br /> the thickness of the sand and gravel will vary between 15 and <br />' 20 feet. <br /> Soils and Overburden. There are three soil map units on <br />' or adjacent to the mining site (see Map Exhibit I-1/J-1). Only <br />' two of the soil units will be affected by mining. The area covered <br /> by Aquolls and Aquents, gravelly substratum, is in the creek <br />' bot toms adjace nt to St. Vrain Creek. This unit covers about <br />' 6 <br />