Agenda - 09-21-1999 - 2 - Laserfiche WebLink

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4. "No downhole distribution of the hydrologic parameters were obtained — no flowmeter. " See #3 above. The potential risk associated with C &D landfills does not warrant such expense at the siting stage. It would take numerous of these flowmeter tests to be able to know much more about groundwater flow at the site than is already known on the basis of existing information. S. "Only one temporal snapshot of the water table was obtained during the dry season. Implications of seasonal water table fluctuations and variability of groundwater flow direction as well as their implications for leaching contaminants from the landfill have not been investigated. " Additional wet season water level measurements will be taken at the site before completion of the second part of the application, the Design Study Application. The Solid Waste Section does not issue landfill permits unless wet season water level information has been collected at a site. In addition, the applicant must submit and analyze sufficient archival meteorological data and regional recording well hydrograph data to support a conservative estimate of future long -term seasonal high water levels beneath a site. Design base grade elevations are required to be a minimum of four feet above these conservatively estimated long term high elevations, to prevent the interaction of waste and groundwater and minimize leaching of contaminants. 6 "Wetlands within the landfill indicate groundwater- surface water interactions, yet their implications for contaminant transport have not been investigated. Groundwater level map seems to be rather inaccurate. For example, it does not indicate any influence of the wetlands. " A properly constructed groundwater level map based on July conditions at the site should not reflect any influence of the wetlands. At the time represented by the water level map (July) the areas classified as wetlands on the site, each smaller than one -third acre, were dry. During July hand auger investigations within the delineated wetland areas, we did not locate any confining layer that would indicate perching of groundwater, nor did we encounter moist soils indicating discharge of deeper water. Water levels in our wells near the wetland were well below ground surface. Our water level maps and cross sections do, however indicate the influence of the pond on the site. The groundwater level map required for the Design Study will be based on wet season data, and may reflect some influence of the wetlands at that time of year. 7. "A number of hypotheses were posed in the report and accepted without proof. Also, a number of unsupported statements were included and accepted. " • Our statements concerning the effectiveness of the nearby stream as a downgradient discharge point are based not only on our measurement of vertical gradients in the well pair. The vertical foliation of the subsurface rock units, and the high density of vertically oriented fractures in core samples and site outcrop indicate high transmissivities in the vertical dimension. No shallow confining layer was encountered in the area near this stream. • Our statement that slug test values should be assumed to represent maximum values was meant to reflect our interpretation of results for those wells screened near the transition from regolith to bedrock. Most of the wells in our study were screened in this horizon, as it is a critical horizon, Response to Comments of Dr. Z.J. Kabala C&D Landfill Siting Orange County, North Carolina Joyce Engineering, Inc September 27, 1999