Ecological Evaluation Technical Guidance - State of New Jersey

TOC, grain size, cation exchange capacity, and pH analyses may beconsidered for some soil investigations. These data may provide a qualitativeindication of bioavailability and toxicity. These results may also be used tointerpret borderline exceedances in a weight-of-evidence or professionaljudgment decision (Suter, 1993 and Suter, et al., 2000).III. Background and Reference AreasBasic guidance for background area sampling is provided in Section 5.3.4.The following section describes the suggested reference area sampling to beused in more comprehensive soil sampling programs. When investigating soilcontamination to determine whether it is linked to site operations, and in thedevelopment of remedial goals, it is important to establish the chemicalcomposition of background area soils and assess the site’s contaminationrelative to the regional quality of the upland soil area being investigated.Many of the state’s soils, especially in urban and industrial settings, havebecome contaminated by historic nonpoint source discharges, resulting in thediffuse, anthropogenic contamination of soils at concentrations higher than thenatural background.While it is difficult to distinguish between site and nonsite-relatedcontamination in some settings, a reasonable attempt should be made to do so.If potential sources of contamination are present upgradient of the site, and itis believed that these sources have contributed to soil contamination detectedon-site, these areas should be sampled, and professional judgment shoulddictate how these data are to be interpreted and used. Note that these resultswill not be considered representative of true reference area (i.e., naturalbackground) conditions. To demonstrate that contamination may be causedby natural background, the investigator is referred to N.J.A.C. 7:26E-3.8(a)and 3.8(b).For upgradient and off-site background area locations, the collection of threeto five samples is recommended from each appropriate depth interval toestablish a range of background contaminant levels (the larger number ofsamples is recommended because of soil heterogeneity). Samples should becollected from areas outside the site’s potential influence. The samples shouldnot be collected from locations directly influenced by or in proximity to otherobvious sources of contamination (e.g., other hazardous waste sites, sewer andstormwater outfalls, agricultural areas, other point and nonpoint sourcedischarges). At a minimum, upgradient and local background area samplesshould undergo the same chemical analyses as site-related samples.Additional determinations, such as terrestrial floral and faunal structure, maybe required on a case-by-case basis.Given that soil investigations can include community surveys, toxicity tests,tissue residue sampling, and bioaccumulation studies, the identification andselection of appropriate reference area samples is a key component to considerwhen developing a soil study design. Testing of reference area soils providesa measure of relative or incremental risk. Comparisons of test soils toEcological Evaluation Technical Guidance Document 63Version 1.2 8/29/12