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<br />-z- <br />I have combined items 3a and 3b and have made an assessment of the effects of <br />mining upon flow in the Rapid Creek-Cottonwood Creek stream-alluvial aquifers <br />system. (See attachment.) The analysis shows that, in the absence of sub- <br />sidence or flow through natural factures, changes in flow would be insignificant, <br />and there would be no material damage to downstream users. The applicant will <br />be mining beneath the stream valleys according to a limited extraction plan. <br />Therefore, possible subsidence effects should be avoided. The possibility of <br />flow through natural fractures is difficult to predict. Major fractures such <br />as a fault would normally be identified during resource evaluation, and none <br />has been identified by the applicant. Minor fracture (jointing) is ubiquitons <br />in sedimentary rocks. However, joints may be open or closed to the passage of <br />water. Their effect cannot be accurately predicted, but can be monitored. It <br />is therefore appropriate to monitor the stream-alluvial aquifer system during <br />mining and reclamation, and to identify the appropriate mitigations that would <br />be undertaken should monitoring identify an undesired effect. <br />The applicant's assessment of water quality effects resulting from leachate <br />from the coal waste pile is fairly conservative, but fails to take effects <br />upon TAS into account. It is my understanding that you will be expanding the <br />assessment yourself to examine the potential increase in TDS. <br />The applicant has agreed that the Division should stipulate an appropriate <br />monitoring plan (Item 4), and mitigation plan (Item 5) as a part of the <br />finding's document. The surface water monitoring should include three gauging <br />stations,onedownstream of the permit area, and two stations upstream of the <br />permit area on Rapid Creek and Cottonwood Creek. The measuring devices should <br />be sired to show seasonal variations and must provide accurate measurement <br />during the low flow periods which would be the most likely affected by mining. <br />The gauging stations should be equipped with continuous recorders, and the <br />data submitted to the Division on a quarterly basis. The monitoring plan should <br />be submitted to the Division for review within 60 days of permit approval, and <br />should be installed and operable by March of 1983. (Consult with Roy Cox to <br />see what monitoring might be necessary to protect the downstream alluvial well.) <br />Within 60 days of permit approval, the applicant should submit a contingency <br />plan describing the measures that would be undertaken by the operator to <br />provide water to downstream users should the operators surface and ground water <br />monitoring indicate that the mining operation is being an adverse effect upon <br />those users. <br />If you need any additional information or analysis from me to complete the <br />hydrology sections of the finding document, let me know. I will be making the <br />AVF findings for the Cottonwood lease during the next few days and will provide <br />you with a copy next week. <br />cc: Brian Munson <br />Jim Pendleton <br />Attachment <br />