2008-04-15_REVISION - M1980244 (368)

Home Browse Search

Monitorin4 Well and Piezometer Closure Costs Per information provided by Jeff Campbell to M. Ellis on February 18, 2008, there are 49 monitoring wells ranging in • diameter from 4 to 6 inches and from 50 to 250 feet deep. There are also 15 piezometers that are shallow (20- 40 ft deep) and they are mostly 3 inch diameter holes. Therefore, use 49 wells and 15 piezometers for costing purposes. Assumptions: (1) the closure of the monitoring wells involves cutting conduits off at ground level, (2) filling with bentonite chips from bottom of the well to within five feet of the surface, and (3) putting in a plug of concrete of 5 feet depth on top of the bentonite and extending to the surface to create the necessary seal and closure of the hole. This procedure would comply with Colorado State Engineer's Office Rule 16-Standards for the Plugging, Sealing, and Abandoning Wells and Boreholes. To be conservative, assume each of the monitoring wells is 250 feet deep and 6 inches diameter. To be conservative, assume each of the piezometers is 40 feet deep and 3 inches diameter. Monitoring Wells Number of Wells? Well Depth bentonite chips (ft)= Well Diameter (ft) _ Calculated volume chips (cu ft) _ Density of bentonie chips (pcf) Pounds of chips required = Depth of Concrete Plug (ft) _ How many bags concrete? How many yards of sand? Backhoe hours per hole = Laborer hours per hole Piezometers Number of Piezometers? Piez Depth bentonite chips (ft)= Piezometer Diameter (ft) _ Calculated volume chips (cu ft) _ Density of bentonite chips (pcf) Pounds of chips required = Depth of Concrete Plug (ft) _ How many bags concrete? How many yards of sand? Backhoe hours per hole = Laborer hours per hole 49 wells Provided by CC8~V Env Staff 245 ft Assumed conservatively for each well 0.5 ft Measured 48.1 cu ft Diameter x Depth 69.25 Ibs/cu ft Cetco Volclay Medium Bentonite Chips 3330 Ibs/well Volume x Density 5 ft Required by Rule 16 State Engineers Office 2 bags/well Enough to make 1 cu ft of plug + small cap 1 cy/hole Estimated by MDE 2 hrs/well Estimated by MDE 4 hrs/well Estimated by MDE 15 piezometers Provided by CC&V Env Staff 35 ft Assumed conservatively for each piezometer 0.25 ft Measured 1.7 cu ft Diameter x Depth 69.25 Ibs/cu ft Cetco Volclay Medium Bentonite Chips 119 Ibs/piezo Volume x Density 5 ft Required by Rule 16 State Engineers Office 2 bags/piezo Enough to make 1 cu ft of plug + small cap 1 cy/hole Estimated by MDE 2 hrs/piezo Estimated by MDE 4 hrs/piezo Estimated by MDE Activity Work Hours Eqmt Cost Labor Cost Material Cost Total Cost Monitoring Well Closure Cut-off pipe, capping, and plugging with backhoe' 98 $ 3,416 $ 2,849 $ 33,448 $ 39,714 Labor for plugging & capping 196 N/A $ 4,077 N/A $ 4,077 Piezometer Closure Cut-off pipe, capping, and plugging with backhoe' Labor for plugging 8~ capping '80 H.P. Backhoe (2008 Means, p 449) 30 $ 1,046 $ 872 $ 607 $ 2,525 60 N/A $ 1,745 N/A $ 1,745 Subtotals = $ 4,462 $ 9,543 $ 34,055 $ 48,060 Well and Piezometer Closure Total Cost = S 48,060 Rental Rental Cost Operating Labor Monthly Hrs/month $/hour $/hr $/hr $ 2,950 176 $ 16.76 $ 18.10 $ 29.08 MDE (2-21-08)