Laserfiche WebLink
• <br /> <br />ExxonMobil Global Services <br />Colony Shale Oil Project <br />ESR Reclamation Studies <br />Weighing Lysimeter Performance 1990-2003 <br />Project No. 353 <br />Page 17 <br />the re-wetting of the shallow soils about a month earlier than usual re-wetting of the shallow soils. <br />These events also appear to have caused a slight re-wetting (1% to 3%) of the uppermost ESR <br />combusted shale layer, but not further down in the spent shale. Conversely, in the drought years of <br />2001 and 2002, summer thunderstorms large enough to produce runoff did re-wet the shallow soils <br />but did not re-wet the underlying spent shale. In 2005, a relatively wet yeaz for which only <br />precipitation data is not reported here, summer thunderstorms that produced significant runoff <br />apparently did not re-wet the underlying spent shale. <br />Conversely the topsoil and underlying "mixed" wne always gain moisture in the spring melt, <br />although the magnitude of the increase is much greater in shallow soils unti11999. After 1999, which <br />was in the trailing portion of a 6 yeaz wet cycle, the "mixed" wne begins to exhibit a greater moisture <br />change (wetting and drying) than the overlying topsoil zones. Recalling that this zone is an attempt to <br />simulate the inevitable mixing of some ESR combusted shale into the topsoil layer being spread over <br />it, it is interesting to observe this clear step change. It may be that the salts associated with the ESR <br />combusted shale minerals may have been leached out after years of spring melt percolation or <br />hydrated to the point at which this wne became tolerable for plant roots. As such, given its loam <br />textural chazacteristic, it may have become a significant participant in the plant demand component of <br />evapotranspiration This time frames coincides with a general ascendancy of deeper rooted plants, <br />including mainly the shrub species, based on cover and density measurements by others (W. <br />Keammerer). This trend is also appazent in the photographs presented in Appendix C. <br />4.2 Comparison to EPA's HELP Model <br />We have run the HELP model (Hydraulic Evaluation of Landfill Performance) using the soil <br />• <br />parameters inferred form the 1987 ESR characterization (WWL, 1987), and site specific temperature <br />and rainfall data. It should be noted that the HELP model is structured for use as a statistical <br />simulation. It takes the user's input data and produces statistical variations around that data, and then <br />runs the simulation for 100 years to arrive at an average performance for consideration in landfill <br />LACHEL FELICE & Associates <br />