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e 2 • ~, b, 1983 Peter O'Connor Chieftain Mine We therefore are willing to adjust the topsoil stockpile seeding rate to the following, This is prepared in accordance with S.C.S, Colorado Agrono:gy Note No. 61 (Seeding Rates) and allows for very nearly 80 seeds per square foot. s e~ ties Fairway Crested Wheatgrass Intermediate Wheatgrass Yellow Sweetclover rate (lbs. PIS/acre - broadcast 8 8 1.4 17.4 We also wish to point out that your proposed changes in the seed mixture and rate only allows for 77.18 seeds per square foot whereas our adjustment provides 79.98 seeds per square foot. A small difference to be sure, but perhaps important. Also, your contention that the original rate only allowed for 46 seeds per square foot is in error. It appears that you must have used the seeds per pound quantity for Standard (190,000), whereas Fairway has (302,000). In fact, our original rate allowed for just under 60 seeds per square foot (see S.C.S. Colorado Agronotgy Note No. 61, March 16, 1981). Exhibit E -Reclamation Plan, Item 1: There are several reasons why we planned the topsoil distribution the way we did, The primary reason for placing most of the soil on the slopes stems from a principle that the quantity of soil needed is primarily determined by the water holding capacity of the soil. If the soil depth is insufficient not only is its nutrient value reduced, but it may be unable to store sufficient water for drought periods so shallow rooted plants are not harmed. Since the application was last submitted some soil and soll~spoil mixtures were sampled and tested at C.S.U. The results are attached. The soil tends to be a clay loam while the soil spoil mixtures are a sandy clay loam. Although not yet identified by the S.C.S., the soil on this area may be similar to the Kutch clay loam which commonly occurs in these locations relative to the Dakota Sandstone hogbacks. This soil has an available water capacity of about 0.16 inches per inch of soil, xhich is about average for a clay loam. Assuming Robinson Brick Company were to agree to placing 4 to 5 inches of soil on the slopes then the soil would be able to hold only about 0.7 inches of water. Although probably adequate for slow vegetation development a much better rate of development can be achieved with somewhat more moisture reserve. With eight to ten inches of soil the available capacity is about 1.25 inches which provides for a surplus on north and east facing slopes and a generally adequate amount on south and west facing slopes in the 3:1 to 5:1 range. Also some interesting shifts in species composition can occur if the available moisture for shallow rooted plants is insufficient. In time, the deep rooted plants can become increasingly dominant, In spoil materials such a shift is highly desirable in helping initiate some efficient nitrogen cycling, but in soil this is not desirable because nitrogen cycling is not that much of a problem. A few more inches of soil can store enough water to allow the grasses to become stronger and able to compete with deep rooted plants more effectively. This keeps a better balance in the species composition.