Data evaluation and data gaps

Existing data for concentrations of contaminants in the medium of concern—surface soil, subsurface soil, groundwater, and air—are evaluated. This evaluation will determine if data are adequate to estimate exposure point concentrations and to evaluate contaminant migration and toxicity. Existing data will also be evaluated to determine if data are of ade­quate quality for use in a risk assessment according to the methods specified in the U.S. EPA guidance, Data Usability in Risk Assessments.

If additional environmental data are necessary to complete the BLRA, an SAP is devel­oped. In addition to chemical data, collection of water quality data (i.e., hardness) may be specified in the SAP because the toxicity and mobility of metals in surface water is hard­ness dependent.

At this time an evaluation of existing data indicates that on-site groundwater data are available. Current groundwater data and new empirical data are evaluated for background and down-gradient information. The arithmetic means and 95% UCLs of the mean are cal­culated for COPCs. For the groundwater pathways a well survey is conducted within 1 mile of the site to verify the locations and uses of all wells.

If recontouring of the soil surface has occurred to direct storm water runoff toward col­lection points, additional surface soil samples (0-2 in.) may be necessary for the analysis of COPCs in the soil ingestion and air pathways.

Data collection points are designed to identify hot spots and to calculate average con­centrations over the entire site and in the areas of concern. Soil pH must also be measured because soil pH influences metals transport.

Surface water data for up-gradient and down-gradient points and sample collection points for this data are identified. No surface water or sediment data from on-site

drainages, or drainage pathways from the site, may be available to provide information on the extent of contaminant migration. Sediment data from the surface water pathway pro­vide information on whether the rivers or standing bodies of water subject to runoff are another source of contamination to other surface waters. Collect surface water and sedi­ment samples from these areas.

The level of generation of dust at the site is required information. This information may be collected via real-time particulate measurements and/or by collecting samples for lab­oratory analysis. The level of dust generation is assumed to vary significantly with time and climatic data. The collection of dust generation data is planned carefully so that dust generation is neither underestimated or overestimated.

Дата добавления: 2015-11-16