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.... DEC-29-'94 THU 89:39 ID:C D 8 M RALEIGH N C FAX NO:gig-?81-5?30 ~173 PO? without prior written approval from the County. CDM will review all invoices received from the drilling contractor to ensure that dr~lllng footages and other charges are correct. Once reviewed and approved, invoices from the drilling contractor will be passed through to the County. Ta~k 3.3 - Supervision of Geotechnical Drilling Work Once the boring plan is approved by the SWS and a qualified drill~,g contractor is selected. CDM will implement the approved boring plan. A CDM geologist will initially visit the site to review and stake.out ~e boring locations and coordinate with County staff ~a providing access to bo .r~ng locations. A CDM geologist will supervBe the drl/llng contractor during field operations a~d determine sample collection depths and piezomcter installation depths. CDM will obtaJ0a information on fractured bedrock conditions by collecting rock cores to provide information on: · ~ Rock types · R¢covel7 vala~S · Rock Quality Des~nafion (RQD) values · Saturated hydraulic conductivity and secondary porosity · Rock descriptions including ft~Jring and jo~ting, patterns A CDM geologist will also conduct the necessary tests to de~-~i~ne hydraulic conduetivky of the aquifers as requested by the SWS. CDM will collect static water levels from each of the new and existing piezometers at the time of boring, at 24 hour~, and at 7 days. It is assumed that County staff will continue to collect monthly water levels on both the new and existing piezome~e~s thereafter for at least 18 months ~n order to obtain information on t. he seasonal high water table. Task 3.4 · Reconnaissance Magnetic Survey Geologic maps of the landf'fll site region indicate the possible oocurrence of diabase dikes in the vicimty of the Cabarms County land_filL A diabase dike is basically an area where molten material has intruded into rock near the surface. [gabase dikes are often preferential paths for ground water flow. For this reason, the SWS is likely to request that a surface geophysical survey be conducted to determine the existence of diabase dikes on the propos~ sites. The purpose of the magnetic survey will be to provide geophysical evidence of the presence or lack of fliabase fl/kcs at the proposed site. CDM will retain a qualified subeonsultant to perform the magnetic survey. The cost for the survey is included in the allowance for geotechnical clrini,~g work in Section 4 of this Ameadment. The scope of services for the magnetic survey work will ~nclude the following: 3.4.1 Review of Available Aerial Mamaetic D~ta. CDM's subeonsultant will acquixe and review available aerial magnetic data of the Cabarrus County Region. This review will precede any geophysical field work and be incorporated into the approach of our survey. Page 5 of 17