1995-03-17_GENERAL DOCUMENTS - M1973021

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Cooley Gravel Company 17 March 1995 Page 4 of 9 Morrison Quarry - 1994 Annual Report the core borings is approximately 70 to 75 percent, indicating fair to good quality rock. It should be noted that drill core RQD data alone is a limited means of evaluating rock quality and judgement about other factors such as rock strength,joint character and ground water conditions are also utilized in slope stability evaluations at the site. Water Level Data Supplemental information regarding ground water conditions in the vicinity of the Central Quarry; that was obtained during the 1994 operation year was already provided to DMG as part of the Adequacy Review Responses for permit Revision No. AM-004. A letter from Haley & Aldrich to DMG, dated 1 February 1995, included supplemental hydrogeology information based, in part, on the four core borings discussed above. This information was originally included in a letter report on annexation feasibility and cost estimates for the Central Quarry Reservoir dated 12 September 1994. An updated assessment of site hydrogeology conditions and an overview presentation of hydrogeologic investigative data collected during calendar year 1994 was presented. An excerpt from this document is resubmitted herein as Attachment B, Supplemental Hydrogeologic Information, for your convenience. Additional details concerning measured water levels and bedrock permeability tests are included together below in the discussion of packer testing conducted in the four exploratory core borings. Packer Testing A total of eighteen packer permeability tests were conducted in three of the four exploratory core borings drilled during 1994 to evaluate bedrock permeability as part of conceptual design of the proposed reservoir that may be constructed in the Central Quarry. These tests resulted in Haley & Aldrich estimating an average permeability of the rock mass in that area of approximately 1 x 10-1 cm/sec. This section provides more detail on the water level and packer test data that were the basis of that estimate. Packer tests were conducted in core borings CH-CRI, CHR-2 and CH-CR4. No tests were conducted in core boring CH-CR3 because the boring was covered by flyrock from a production blast following coring, but before testing could be accomplished. Static ground water levels were measured in all four core borings during and after drilling and packer testing. Representative ground water level data for the borings for July 1994 are as follows: Borina Ground Surface Depth to Ground Water Elevation(ft) Water ft Elevation(ft) CH-CR1 6462.1 4 6458 CH-CR2 6604.4 68 6536 CH-CR3 6491.2 10 6481 CH-CR4 6558.5 90 6469 RP08267.200 4