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

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Responses to specific comments by Dr. Z. J. Kabala: Every single one of the points in Dr. Kabala's review are well known to the community of environmental consultants, regulators, and university faculty members who work on groundwater problems in the Piedmont of North Carolina. This community of practitioners maintains an open dialogue in daily efforts to write, implement, and meet effective environmental regulations and policies. These efforts aim to match the levels of detail and effort to the level of potential risk at any given site. An example of this process is NCDENR's review of our investigation plans prior to drilling at the two Orange County sites. 1. "Only much less than 0.5% of the proposed area has been hydraulically tested." The calculations presented by Dr. Kabala imply that the required goal of our study is to create a quantitative model of groundwater flow at the site. This is not the case. His contention that we achieved only 0.35% of this goal obscures the fact that landfill siting study requirements are designed to reach a different goal. That goal is to delineate the nature of and limits of groundwater flow paths at the site. This goal is met through gathering and analyzing water level data, geological data from the literature, outcrop, drill core, and auger cuttings, grain size analyses, topographic data, and the other types of information presented in our report. Groundwater flow at landfill sites is to be characterized not only through the use of numerical models based on well test information from slug tests or pumping tests. Such reasoning would require several hundred wells at the Guess Road Site. 2. Accuracy of Slug Tests A large portion of Dr. Kabala's presentation consisted of his criticism of our use of slug tests. He implied that these tests form the only basis for our site characterization, by ignoring much of the careful and informed geological reasoning and data contained in the report. JEI and State regulators, are familiar with the references he cited and fully aware of the limitations of using slug tests. In landfill siting studies, slug tests are used mainly to provide a relative comparison of the transmissive capability of the soil profile at different depths. JEI employed the Bouwer and Rice method, which is recommended by NCDENR for such purposes in shallow wells. We have attached a policy memorandum issued by the Groundwater Section of NCDENR, that concerns applicability and acceptable methods for slug tests in groundwater investigations. The comparative study of slug test methodology contained in the book (Butler, 1998) cited by Dr. Kabala is based on tests performed in a shallow sand aquifer, and the comparison is not valid for weathered crystalline rock 3. 'Wo large scale testing was performed —no pumping tests." Dr. Kabala argued that the risk of dissolved arsenic from pressure - treated wood reaching the Little River warranted the use of expensive multiple well pumping tests. To our knowledge, such tests have not been employed prior to siting a landfill anywhere in this state. These tests are normally only required at sites where groundwater contamination has been identified, and where that contamination poses an imminent threat to public health and safety. See the attached Policy Memorandum referenced above. Response to Comments of Dr. Z.J. Kabala 2. Joyce Engineering, Inc C&D Landfill Siting September 27, 1999 Orange County, North Carolina