6.6. SR 03-15-2010 - Laserfiche WebLink

Home Browse Search

Page ~ of 6 fetter to fir, Jah~t ~~~5 11~Y~r. Matt ~edvina R~: Revised s~]A %tydro~eaiug're Evaluation Report ~i6~ River Lar~dfi~i, Inc, approximately 2/3 mile downgradient of the site. The potential for impacts to this welt is very small considering the well cased to a depth of yearly 3~~feet, however ~I~.~ should consider the inclusion of this well in the residential well monitoring program, wI1~T currently ~~.onitors the Ridges of T~.ce T1aI~e community water supply well annually on a voluntarily basis. ~a,~e .~5, ~ontxnuo~s ~lllLayer; ~ discussion is provided regarding the fine grained soil deposits (tills separating the ``upper autwash" unit from the "lower outwash"unit. It is stated that the thickness of till deposits varies from S to more than SD feet at the Site, .l~ figure 15' presents a Till rsopach .dap which shows areas of the site where the till thicl~ness is less than ten feet. Although it is not stated within the text of the report or on .the map, it is implied that the till layer is continuous throughout the site. ~'he available bori~~g data suggest that the till layer is continuous, however, the borings in the west central portion of the site da not extend to an adequate depth to definitely make this conclusion. It should be noted that borings ~, I6(~}, ~4, ~5 to da not provide evidence that the till is continuous. It should be further noted that the geologic crassp sections which depict a continuous till layer for this portion of the site are interpretive, `here exists a passibility that the till is discontinuous at the site and the upper and lower vutwash units are in hydraulic connection. It should be noted that the absence of the tilt layer is the situation which is present for the existing landf ll area in the vicinity of the ~~~ shop, ~iscantinuity of the layer has impl icatians for establishing an effective groundwater monitoring system at the site. Geologic data frog: the recently advanced soil ba~~ings, ~B51 and 5~5~, suggest tbo till xs continuous across the site. ~'~ ~. ~ ~ :-~~ r E 3, ~'a,~e ~0, ~'ror~ndwate~ i,~c~iarge; The report states that groundwater in the north central portion of the site,~ows northwest and is interpreted to discharge to dice Lake/I'ibbits 1~roo1~, It is understand that ~~I has conducted additional site investigation related to the groundwater impacts from the existing waste deposit, Ida data has yet been presented to support this groundwater discharge canclusian, Results of the second and final phase of the Rine LakelTibbits ~roo~ Area groundwater investigation will ~be su~b~itted shortly. Results from the second phase of Investigation support the groundwater discharge Conceptual model, ~. gage ~z, Gror~nc~water anitori~ago Y~.~II proposes the addition of one nested piezometer in the tower outwash to evaluate the hydraulic gradient across the till layer, Given the concerns regarding the continuity of till layer, the piezometer should be utilized as a monitoring well and included in the proposed monitoring work plan. A second nested monitoring well (P3~~C location suggested} should be installed along the western portion of the south boundary for similar gradient and water quality monitoring purposes.