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(Page 2) MINE ID # OR PROSPECTING ID # M-1994-093 INSPECTION DATE 05/03/02 INSPECTOR'S INITIALS ESC This was an inspection of the Dahlia North Resources Pit conducted by Erica Crosby of the Division of Minerals & Geology. Mike Refer and Bill Brown of Aggregate Industries-WCR, Inc. and Andy Legg of the City of Thornton were present during the inspection. The inspection was done in conjunction with the Flanagan Dahlia Pit (Permit No. M-1989-066) and the request for a bond reduction for the installation of the pipeline between the two slurry-wall lined ponds. The City of Thornton requested the release on behalf of the operator. Permit Amendment (AM-02) and Technical Revisions TR-02 and TR-03 were submitted to the Dahlia North Resources Pit to facilitate installation of a pipeline within the permit area and dewatering of an existing groundwater lake. Specifically, AM-02 added one acre of affected land across 88`~ Avenue to connect the Flanagan Dahlia Pit and the Dahlia North Resources Pit. The bond amount associated with AM-02 is in the form of two Third Party Certificate of Deposits; No. 8301567 is in the amount of $100,000.00 and No. 2014124838 is in the amount of $24,500.00. TR-02 revised the permit to install a pipeline to the Dahlia North Resources Pit to the Sprat-Platte Ranch Pit (operated by the City of Thornton, Permit No. M-1986-146). The bond amount associated with TR-02 is in the form of a Third Party Certificate of Deposit No. 2014124820 in the amount of $12,600.00. There was no increase in the bond associated with TR-03. Therefore, the total amount of bond reduction requested for this site is $137,100.00. Andy Legg stated that installation of the pipeline went according to plan. The slurry wall was penetrated and repaired near the northwest corner of the pit. Seepage collars were constructed around the pipeline and encased in cement low-fill to provide a seepage barrier at the area of penetration. R letter dated November 16, 2001 addressed to Andy Legg of the City of Thornton from GEI Consultants, Inc. summarizes the construction methods of the repair of the slurry walls and opinions regarding the damage to nearby wells during the interconnection pipeline project. The pipeline under 88`° Avenue required the area to be tunneled by-hand. Andy Legg stated that grout injections were placed in the hole to strengthen the material under the road. No visible subsidence features were noted and the road appeared to be in good repair. A small ground water lake was temporarily dewatered during construction of the interconnection pipeline. According to the November 16, 2001 letter, water level measurements taken in four wells during the dewatering period noted a drop of 8 feet. Once dewatering ceased and the pond was allowed to fill, the wells showed an increase to the approximate water level that existed prior to the dewatering activity. Andy Legg stated that the property owner to the north was supplied with water during the project. The embankment where the slurry-wall was breached appeared to be in good repair. No springs or seeps were noted in the breached area. The embankment was graded and blends in with the existing slopes. The area has yet to be revegetated, but according to the operator and the City of Thornton it will be completed this spring. The Division feels that the existing bond in the amount of $744,000.00 will cover any additional seeding that needs to be completed. The slurry-wall penetrated on the east side will eventually connect to the Sprat-Platte Ranch Pit. The embankment on this end also showed no signs of springs or seeps, and appears to be in good repair. The operator will need to submit a copy of the slurry wall approval issued by the Office of the State Engineer ("OSE"). Upon the receipt of the OSE letter, the Division will approve the bond reduction request in the amount of $237,100.00 (letter was received by fax on 5-6- 02).