ARCHIVED REPORTS_XR0005851 CASE 2

Home Browse Search

• a collected after a known volume of the water is foreign materials ' evacuated from the aquifer,or the well can be pumped until the stabilization of parameters such as 3 Attach the line to the bailer and slowly lower temperature, electrical conductance, pH, or turbidity until the bailer is completely submerged, has occurred being careful not to drop the bailer to the ' water, causing turbulence and the possible However, monitoring for defining a contaminant loss of volatile organic contaminants plume requires a representative sample of a small ' volume of the aquifer These circumstances require 4 Pull bailer out ensuring that the line either that the well be pumped enough to remove the falls onto a clean area of plastic sheeting or stagnant water but not enough to induce flow from never touches the ground other areas Generally, three well volumes are ' considered effective, or calculations can be made to 5 Empty the bailer into a pail until full to determine,on the basis of the aquifer parameters and determine the number of bails necessary to well dimensions, the appropriate volume to remove achieve the required purge volume ' prior to sampling 6 Thereafter, pour the water into a container During purging, water level measurements may be and dispose of purge waters as specified in taken regularly at 15-30 second intervals This data the site specific sampling plan ' may be used to compute aquifer transmissivtty and other hydraulic characteristics The following well 7 3 2 Submersible Pumps evacuation devices are most commonly used Other evacuation devices are available, but have been The use of submersible pumps for sample collection omitted in this discussion due to their limited use is permissible provided they are constructed of suitably noncontaminating materials The chief 73 1 Bailers drawback, however, is the difficulty avoiding cross- contamination between wells Although some units Bailers are the simplest purging device used and have can be disassembled easily to allow surfaces contacted many advantages They generally consist of a rigid by contaminants to be cleaned, field decontamination length of tube, usually with a ball check-valve at the may be difficult and require solvents that can affect ' bottom A line is used to lower the bailer into the sample analysis The use of submersible pumps in well and retrieve a volume of water The three most multiple well-sampling programs,therefore,should be common types of bailer are PVC,Teflon, and stainless carefully considered against other sampling ' steel mechanisms(bailers,bladder pumps) In most cases, a sample can be collected by bailer after purging with This manual method of purging is best suited to a submersible pump, however, submersible pumps shallow or narrow diameter wells For deep, larger may be the only practical sampling device for diameter wells which require evacuation of large extremely deep wells(greater than 300 feet of water) volumes of water, other mechanical devices may be Under those conditions, dedicated pump systems more appropriate should be installed to eliminate the potential for cross- contamination of well samples 73 11 Operation Submersible pumps generally use one of two types of Equipment needed will include a clean power supplies, either electric or compressed gas or decontaminated bailer, Teflon or nylon line, a sharp air Electric powered pumps can run off a 12 volt DC knife,and plastic sheeting rechargeable battery, or a 110 or 220 volt AC power supply Those units powered by compressed air ' 1 Determine the volume of water to be purged normally use a small electric or gas-powered air as described in 8 0, calculations compressor They may also utilize compressed gas (i e,nitrogen)from bottles Different size pumps are 2 Lay plastic sheeting around the well to available for different depth or diameter monitoring ' prevent contamination of the bailer line with wells