2001-04-03_GENERAL DOCUMENTS - C1984065

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Closure will be accomplished by filling the subsidence feature with materials slurried up the hill via a pumping apparatus or by other means. The materials introduced into the hole must be capable of attaining a minimum compressive strength of 125 psi within twenty-eight (28) days. Materials This Invitation and Bid assumes the use of fly ash as a backfill material. However, any cementicious material capable of attaining a minimum compressive strength of 125 PSI within twenty-eight days is acceptable for use. If materials other than fly ash mixed to the proportions specified herein are proposed for use, the material description, method of placement and compressive strength characteristics must be submitted along with the Bid Schedule for evaluation by the Owner. Acceptable backfill material includes, but is not limited to, fly ash mixed with cement and water. Fly ash is available from the Excel[ Energy Cameo Generating Station located at Cameo, Colorado, approximately sixty one (61) miles to the west of the Project site on Interstate 70. Excell Energy will make the material available to the CONTRACTOR free of charge. However, the CONTRACTOR will need to provide over-the-road trucks to transport the material to the Project Area, and a loader to fill the trucks at the Cameo Generating Station fly ash disposal site. Excel Energy will require that the CONTRACTOR sign appropriate safety and release of liability documents, and comply with all on-site safety directives when loading and hauling on Excell Energy property. An example copy of the required liability waiver will be provided to the CONTRACTORS at the Pre-Bid Meeting. At the Project site, fly ash will be mixed with Type II Portland cement conforming to ASTM C 150. The fly ash and cement will be thoroughly mixed at a ratio of ninety five percent fly ash to five percent cement (95% : 5%). Potable water will be introduced into the fly ash /cement mixture so that the mixture has adequate slump characteristics which will allow it to be pumped or otherwise transported to the subsidence feature, and yet attain the required minimum compressive strength specification of 125 psi in twenty eight (28) days. Any fly ash or other backfill materials temporarily stored or stockpiled will need to be covered in order to ensure that dust is not generated from the stockpile. Excess fly ash or other backfill materials remaining after completion of the Project will be properly disposed of by CONTRACTOR. Disposal of fly ash may include returning the unused material to the Cameo Generating Station fly ash disposal facility. Contractor will need to contact Excell Energy to arrange for returning excess materials, if this option of disposal is chosen by the CONTRACTOR. Testing Contractor shall take sample specimens of the fly ash grout in cylindrical containers in accordance with ASTM C 31 at the point of deposit as follows: - One sampling consisting of three (3) cylinders, shall be taken and paid for by the CONTRACTOR. - The samples shall be taken in accordance with ASTM C 172. All three sample cylinders will be taken at the same time, one cylinder to be used for a seven-day test, and two for a 28 day test. The average of the 28-day test result will be used for determining acceptance. These tests shall be performed at the CONTRACTOR'S expense in accordance with ASTM C 39 by a materials sampling laboratory of the CONTRACTOR'S choice which meets the approval of the PROJECT MANAGER. 4