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Arsenic and Chromium Investigation, A Nova Case Study

Nova Investigates Arsenic and Chromium at North Carolina Lumber Yard

Nova Consulting Group, Inc. (Nova), was contracted in August 2018 by a developer in Mecklenburg County, North Carolina, to perform a Phase I Environmental Site Assessment at a working lumber yard slated for residential redevelopment. The lumber yard is in the Catawba River Basin’s critical watershed, which provides drinking water for the city of Charlotte, among other municipalities.

In 2004, the EPA suggested that two groups of pesticides used to pressure-treat lumber be discontinued: chromated arsenicals (CCA), which contain copper and some combination of chromium and/or arsenic; and pentachlorophenol (PCP)- a chlorinated pesticide.

Nova’s Phase I investigation found that CCA, PCP, and lumber pressure-treated with copper-based compounds had been stored outside at the facility on bare ground for approximately 70 years. Because these chemicals can leach from pressure-treated lumber and contaminate nearby soils and, potentially, groundwater, Nova found this to be a recognized environmental condition and recommended a Phase II investigation. The site’s developers and financiers needed confirmation that existing soils could be used in a residential capacity, or have Nova provide a cost-to-remedy.

The Phase II scope was based on potential residential redevelopment. In one day, Nova used a direct push contractor to drill 20 soil borings to a depth of four feet below land surface at locations where CCA and treated lumber had been historically stored. Soil samples were collected at four intervals in each boring (80 samples total). The first two sampling intervals (0-6″ and 6-12″) were chosen for laboratory analysis for total chromium, arsenic, and copper. These 40 samples constituted the first round of analysis. Approximately 25% were also analyzed for PCP and speciated chromium (chrome Ill and chrome VI).

The second two sampling depth intervals (18-24″ and 36-48″) were collected and sent to the laboratory but put on hold, pending round one analyses. This allowed the one-day drilling exploration without the cost of analyzing all analytes at all boring locations and depths—up to a 50% savings in laboratory costs to the client, while maintaining a tight schedule.  If contamination was found at the first interval, the second depth interval samples would be analyzed.

In order to establish background concentrations for the tested metals, scientific literature was reviewed for published information on background concentrations.  Unlike many compounds, metals in soils are largely treated by regulators in context with published background levels.

Two of the 20 soil borings (these were the site-specific background samples) were advanced outside the lumber storage area and sampled in the same manner as the lumberyard soil borings. The background samples were from a nearby residential lot that had a single-family home on it for years prior to being demolished.

Interestingly, the arsenic concentration in the lumberyard soils was not enriched over site-specific background concentrations in our sample analyses, or from cited literature in Mecklenburg County. The chromium results showed that there was no chromium VI measured in the analyzed samples. The chromium III analyses all met North Carolina Department of Environmental Quality (DEQ) residential standards. And, finally, no PCP was documented in the analyzed samples. This meant only the first round of samples had to be analyzed, resulting in significant cost savings for the happy client.

Here is one example of how Nova was able to supply timely information at a reasonable cost to its client by thoughtful sample location strategy. We prioritized the sample location, and analysis, holding samples back for potential analysis, and formulating a step by step analytical regime based on round one analyses. The result is that the client will be able to redevelop the property safely, with minimal cost and without environmental constraints.

 

Author:

Mike Minett smallMike Minett

VP – Mid-Atlantic Regional Manager

Nova Consulting Group, Inc.

704-258-5196

Mike.Minett@novaconsulting.com

 

 

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