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RULE 4 PERFORMANCE STANDARDS <br />Topsoil Stockpile/Pond Embankment Seed Mix* <br />Western wheatgrass @ 4 Lbs PLS/Acre <br />Thickspike wheatgrass** @ 4 Lbs PLS/Acre <br />Yarrow*** @ 0.15 Lbs Pis/Acre <br />*mix will be modified as a result of an updated Reclamation Plan submitted after PR -02 approval. <br />Colowyo existing permit Section 4.06.3 must be modified to reference the updated seed mix in this location at that <br />time. <br />**option to replace Thickspike wheatgrass with Beardless bluebunch wheatgrass or Sheep fescue <br />***option to replace Yarrow with Cicer milkvetch <br />4.05.7 Discharge Structures <br />Please see Section 4.05.7 in Volume 1. <br />The design requirements for sediment ponds can be found in Volumes 2D, 2E, or in Exhibit 7, Item 15, in <br />Volume 13 <br />4.05.8 Acid-forming and Toxic -Forming Spoil <br />Acid forming materials do not exist within the overburden to be removed by the mining operations. A <br />discussion on the overburden at the Colowyo operation has been conducted as set forth in Section 2.04.6. A <br />discussion of the overburden monitoring plan is set forth in Section 2.05. Acid -Base Accounting shows that <br />almost none of the encountered interburden has a net acid -generating potential, and the average acid - <br />neutralizing potential to acid -generating potential ratio ranges from about 50 to about 90 in each borehole in <br />the pit, indicating that there is 50 to 90 times more acid -neutralizing potential than there is acid -generating <br />potential in the interburden (Exhibit 6, Item 6). <br />4.05.9 Post -Mining Impoundments <br />Please see Section 4.05.9 in Volume 1. <br />4.05.10 Underground Mine Entry and Access Discharges <br />Colowyo currently conducts surface coal mining exclusively. <br />4.05.11 Groundwater Protection <br />Please see Section 4.05.11 in Volume 1. <br />4.05.12 Protection of Groundwater Recharge Capacity <br />Please see Section 4.05.11 in Volume 1 <br />4.05.13 Surface and Groundwater Monitoring <br />The current surface and groundwater monitoring program can be found in Section 4.05.13 in Volume 15. <br />South Taylor/Lower Wilson — Rule 4, Page 6 Revision Date: 4/7/17 <br />Revision No.: RN -07 <br />