ARCHIVED REPORTS PR0544112 - Laserfiche WebLink

Home Browse Search

A filter pack shall be placed to enclose the entire Iength of the screened section with an additional 2 feet of filter pack above the screened section. Filter pack material and size is anticipated to be Monterey Sand Number 3. F� Directly on top of the filter pack will be a 2 foot bentonite plug designed to prevent vertical migration of possible contaminants through the annulus. The bentonite pellets shall be emplaced into the annulus by tremie pipe. The remaining annular space(above the bentonite plug to surface)will be sealed using a mixture of 95% Portland cement/5% bentonite powder. This annular seal will be installed by tremie pipe. This seal will be allowed to set for at least 24 hours before any subsequent activities such as well development or sampling. The top of each monitoring well will be protected by a water-tight locking cap with lock and will be inside a flush-mounted, water-tight traffic box mounted in concrete and sloped to about.one-inch above grade to drain away surface water. Each monitoring well location will be surveyed by a California-registered land surveyor for exact surface location and for exact elevation relative to the USGS MSL datum. The elevation will be surveyed at a measuring point marked on the top of the well casing, which is he point from which all water level measurements shall be record:d. 3.5 Well Development Welf development will commence at least 24 hours after installation hof thee:-annular sear. Development will be performed by mechanical.surging:afi&bOjff ..`with a bailer and/or surge block. Evacuation of 3 to: 5 casing volumes f per well is expected. y Tempeafature, .pH, and specific conductivity parameters will be measured in the field during development. . 3.6 Groundwater Sampling .: Each monitoring well will be measured for static water level with a battery-powered sounder before sampling activities begin and after purging, with a precision of+or- 0.01 ft. All measurements will be recorded as depth-to-water from a surveyed measuring point. Depth-to-water readings will be converted to water-levet elevations referenced to the USGS MSL datum. The "standing-water in each well will be purged before sampling. This will begin no sooner than 72 hours following well developrrant. Equipment used will be a Teflon bailer. Each well will be purged until 3 to S well volumes are removed. During purging, the parameters of temperature,pH,and specific conductivity will be measured. Sampling will be performed after these parameter readings have stabilized for 2 consecutive casing volumes. In the event that recharge rates do not permit at least 3 consecutive well volumes to be purged, and the well is purged dry, the sample will be collected after the well sufficiently recovers. The water will be retested for temperature, pH, and specific conductivity after sampling to measure purging efficiency. _10- 172-32-RI 318)91 10- 172-32-R13!8191