ARCHIVED REPORTS XR0008198 - Laserfiche WebLink

Home Browse Search

f w R604 :UPDATE 17 4-27-1993 to ground water data from MW5 is not used; this well was i installed in a slant boring and produces an anomalous high when used. From these gradient lines, data points representing the contact for the proposed contours are plotted along each individual line Once the data points have been plotted between all the wells, the data points representing a given gradient elevation (-45 foot contour, for example) are Connected with site specific factors, "i e " incorporating conditions caused by local geology, hydrogeology, utility trenches, etc . These are used to control the contour between data points This site is presently being influenced by vapor extraction at MW5 , VSB3 , VSB5, VSB9 and VSB11 . A vacuum at these wells and surrounding wells will influence the shape of the ground water surface and subsequent flow directions of the ground water To obtain representative measurements that show the influence by the vacuum extraction at this site, a vacuum measurement is obtained at the well head before removing the cap and the subsequent depth to water measurement is corrected for the negative vacuum head (potentiometric head) . Vapor Recovery System and Monitoring: As stated in the Update Status Report #11, SB3 , SBS , SB9 and SB11 were converted into vapor extraction wells on July 22, 1992 (VSB3 , VSB5, VSB9 and VSB11) Along with MWS, these wells are manifolded to a vapor extraction system with individual valved orifices for flow control and measurement from the individual wells . The individual wells are fitted with a PVC tee head with a locking air tight cap, for well access . The tee lateral (2 inch) is fitted with a 1/4 inch pipe zo tubing fitting for obtaining vacuum/pressure and temperatuae readings . A pipe to hose 2 inch union is placed between the 'tee and the 2 inch PVC flex hose that connects the well to the extraction manifold. At the manifold the .individual wells are connected to their own 2 inch PVC riser (36 inch in height) with an orifice plate and a gate valve at the top of the riser. Vacuum/pressure ports are located on either side of the orifice plate Each orifice (well) has its own manometer (calibrated in millimeters (mm) water) which are connected to the ports for continuous measurement of flow from a particular well All the extraction wells are manifolded together above the gate valve to a set of two orifice risers that are in parallel before the vacuum pumps . After the vapor stream leaves the manifold, it flows through a moisture drop out drum (55 gallon 17E) and then is pulled into the pumps (two Rotron DR505 placed in series) before entering a second moisture drop out drum and then into activated charcoal vapor scrubs . If breakthrough occurs through the 1st carbon, this carbon is removed from the system The #2 carbon is then placed at the #1 position and a new carbon placed on the exhaust as the #2 carbon. A portable ambient air PID-GC (Photovac 10550 packed column) was used at the site to sample for breakthrough of the carbon scrubs, the influent and effluent of the system, and the influent from • the various vapor extraction wells Before sampling the wells or the system, a calibrant made from fresh gasoline is in3ected into page 4