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