ARCHIVED REPORTS XR0008521 - Laserfiche WebLink

Home Browse Search

Geo4ica[Tecknics Inc. Page 3 Valentine(Eldorado St.) Work Plan Addendum#2 Project No. 723.2 February 15, 1999 Monitoring Well Construction The monitoring wells will be constructed using 2.0 inch inside diameter PVC casing with flush threads. The screened intervals will be 5 feet in length. The exact depth interval will be determined by the geology in the field in consultation the supervising geologist and the county inspector. The screen intervals will target course-grained units of the aquifer. Construction is proposed as follows: • Casing will be 2.0-inch diameter schedule 40 PVC with flush threads. • Screened intervals will be 5 feet in length. • #12 sand filter pack will surround and extend two feet above the 0.010" screened intervals. • A decontaminated surge block will be used to achieve a maximum density filter pack. • Three feet of Pel-Plug weighted bentonite pellets will be added to the top of the filter pack. • Surface seal will be achieved by pumping a neat cement grout (augmented with < 4% bentonite) via a tremie tube. • The wells will be secured with a locking watertight cap encased in flush mounted traffic rated well boxes. The table below shows well construction. See Figure 4 for a schematic of monitoring well construction. Well No. Dia./TD Screen Slot Sand Pack Trans. Seal Grout Seal MW-101 2"/90' 85-90' 0.010" #12 sand 83-90' 80-83' 80-surface MW-201 2"1110' 105-110' 0.010" #12 sand 103-110' 100-103' 100-surface After the well sealing materials have set (>24 hours) the wells will be developed (using mechanical surging and pumping methods) until a clear stream of water is obtained. The wells will be purged and groundwater samples collected no sooner than 48 hours after well development. All development and purge water will be containerized in 55-gallon DOT approved containers and stored on site until their disposition can be arranged. A licensed competent surveyor will survey the top of casing measuring point for the well into the common arbitrary plane of the existing monitoring wells. Groundwater Sampling Procedure The groundwater in the new wells will be sampled no sooner than 48 hours after well development and from there after on a quarterly basis. The following is a procedure for the sampling of groundwater from the well: . Before sampling is attempted the wells will be sounded for depth to water and then a clear disposable bailer will be used to determine if floating product is present. The wells will be purged of at least 3 well volumes of stagnant water using either a Wattera purging system or a submersible pump. The Wattera system uses a length of poly tubing with a check-ball on the bottom. The tubing is agitated in an up and down movement, which causes the water to rise in the tubing. This system has been found to be very time and cost effective at sites that �. have problems with silting of the wells.