FURTHER CHANGES, CLARIFICATIONS ETC. IN OUR HYDROGEOLOGICAL UNDERSTANDING OF THE ELMIRA AQUIFERS

Starting on page 18 of the Remedial Action Plan Design Review (Sept. 25/15) we learn that the contaminant plumes have stratified ie. they are not all one heterogeneous concentration of NDMA for example from the top of the Municipal Upper Aquifer down to the bottom. Using VAS (vertical aquifer sampling), CRA (GHD) have determined that there is a corelation between increasing depth and increasing contaminant concentrations in many monitoring wells.

page 20: "Both NDMA and Chlorobenzene concentrations increased with depth, and the greatest concentrations occur in the VAS collected from 29.9 m bgs (at the base of the MU). This corresponds to a coarse basal layer of gravel observed in this portion of the MU.".

page 22: "There were ten locations where NDMA was detected in more than one of the MU VAS and at eight of these locations NDMA concentrations increase with depth. Chlorobenzene was detected in the MU VAS at six locations and the chlorobenzene concentrations increase with depth at all but one location." "Therefore plume stratification appears to occur where sufficient aquifer thickness exists and when stratification occurs concentrations tend to increase with depth.".

page 23: The suggestion is made that "Together W5A, W3 and E7 contained the limits of the NDMA plume in the Bedrock, as shown on Figure 2.17.". A few years back I'd have expressed my disbelief that the Bedrock Aquifer was remotely "contained" at all. Indeed W5A pumps in the ML (municipal lower) and there is no Aquitard (lower permeability zone) between the ML and the Bedrock Aquifer. E7 has had a significant LAT (lower aquitard) between the ML and the Bedrock on CRA's subsurface cross-section maps for most of the last twenty-five years. However of late that LAT has been being interpreted as much thinner. Finally W3 still gives me huge problems. It pumps in the MU (municipal upper) and there is no ML present plus there is a huge LAT between the MU and the Bedrock Aquifer. This should isolate pumping in W3 (MU) from having an effect upon the Bedrock Aquifer.

pages 32 & 33: These pages discuss contaminant penetration into the aquitards. The depth of penetration is a function of the dissolved contaminant concentrations with lower concentrations penetrating approximately .5 metre and higher concentrations up to a metre into the Aquitard.

Page 34: In locations on the Chemtura site where the UAT (upper aquitard) is less than a metre thick essentially high concentrations of NDMA and chlorobenzene are going clear through the UAT from the UA (upper aquifer) into the MU (municipal aquifer).

page 36 : We are advised that there are eleven different pumping scenarios from the Base Case Scenario to adding one or more of the new pumping wells in sucession. These new pumping wells include W8 (Yara), W9 (west and slightly south of W8), W6 (Oriole Parkway east of Arthur St.) and W7 on Sandpiper Place.

Figures 4.1 to 4.8 I can only describe as bizarre. These are a series of the different pumping scenarios both in the MU and the ML for both NDMA and Chlorobenzene individually. For example Figure 4.1 is titled "Base Case To Scenario 7 2028 Simulated NDMA Concentrations In MU". Figure 4.2 is titled "Scenarios 8 To 11 2028 Simulated NDMA Concentrations In MU". These certainly appear to be CRA's (GHD) own computer predictions as to which of the various pumping Scenarios will achieve aquifer (MU & ML) drinking water standards by 2028 first for NDMA and then for Chlorobenzene.

This is where it gets bizarre. I downloaded all eight maps and I'm studying them. The drinking water standard for NDMA is .009 ppb and for Chlorobenzene is 80 ppb.. Now unless CRA has mislabelled these maps' contour lines or they have lost some clarity in being downloaded and printed out, then the results are pathetic. I will be going back and rereading the maps on my computer screen but what I'm reading in my downloaded maps basically states that no scenario (of 11) will reduce NDMA to .009 ppb or less for all the Elmira aquifers and Chlorobenzene appears to have possibly one or two scenarios alone in the ML which will reduce Chlorobenzene concentrations to 80 ppb. or less for the whole ML.

As I said bizarre. Further reading will continue.