Hazard Identification and the Rocky Mountain Arsenal

Of the four stages of the quantatative risk assessment process (hazard identification, exposure assessment, toxicity assessment, and risk characterization), I am most familiar with the hazard identification stage. I've worked for seventeen years for an environmental consultant, and I performed a lot of investigations at a nearby Superfund site known as the Rocky Mountain Arsenal (RMA). RMA is a large (27 square mile) area northeast of Denver that was considered one of the most contaminated places in the United States. To the right you can see that the location was close to metro Denver.

Source:http://www.aaccessmaps.com/show/map/denver_metro

I wish to use RMA as an example to discuss Hazard Identification from our handout. The primary goal for hazard identification at a hazardous waste site is to find out what contaminants are there, and where are they. This can be much more difficult than it sounds and can end up costing a lot of money.

Taking RMA for our example, we will look at how they came to know what they had to clean up. When the government began to suspect that there was a problem at RMA they went back over the history of the site. RMA was founded in 1942 at the start of World War II. Its purpose was to manufacture, and when necessary, demilitarize, blister chemical agents and incendiary weapons. It made mustard gas bombs and phosphorus munitions in case Germany or Japan used them on us. They were manufactured in the southern section of the facility known as South Plants.

source: http://www.fws.gov/rockymountainarsenal/Cultural/CR.htm

In the 1950’s it began production of Sarin nerve agent, while parts of the facility were leased to Shell Oil Company to produce pesticides. A new facility called North Plants was built and the older section was turned over to Shell. The picture on the right shows North Plants. Source: http://www.globalsecurity.org/wmd/facility/rocky.htm

Wastes were dumped into unlined pits or buried. Below you can see the pits (known as Basin F) two blocks north of the large lake in the picture below.

Source: http://www.globalsecurity.org/wmd/facility/rocky.htm

In 1975, the government began to investigate the site, but where would you even start? As Table 14-2 from the handout shows us, once you have the site history and land use, you need to collect samples from the various media. The investigation included several rounds of surface, subsurface, and surface water investigations. The site, being so large, had to be divided into smaller operable units based on location, media, types of contaminants, and similar type variables. My office was involved in much of the investigation, and I installed many groundwater monitoring wells there. I participated in some of the sample collection efforts including surface soil, subsurface soil, surface water and the massive groundwater sampling programs. Some wells were so contaminated that they required us to be in full level B protection (supplied air with full suit on).

To gather the correct information you have to plan your sampling well. At RMA, soil and water samples were analyzed for a wide range of analytes including chemical agents, volatile organic compounds, metals, pesticides and associated breakdown products. It was an iterative process and sometimes analytes would be added or dropped as necessary. There were very specific protocols to follow so that your information would stand up in court. Well over a hundred groundwater monitoring wells were installed and soil samples filled a warehouse on RMA.

By the time the government signed a Record of Decision (ROD), there were more than 65 analytes that were contaminants of concern including nerve agents, blister agents (mustard gas and Lewisite), metals, volatile organic compounds including chlorinated solvents like tetrachloroethene (PCE), arsenic, pesticides, and associated breakdown products of these compounds. The contaminants were found in all media including air, soil, sediment, ground water and surface waters, as well as free products in waste liquids and solids. The ROD has a detailed risk assessment which could be very informative for someone wanting more detail. It can be found at http://www.epa.gov/superfund/sites/rods/fulltext/r0896128.pdf
Risk assessment pages 16-26 of 179.

Finally for this portion of the investigation you have to understand the geologic, hydrogeologic, atmospheric and topographic components of the site. Data obtained from the drilling and monitoring of the groundwater wells provides much of this information. Key information would be items such as the following:

Where does the water flow? How fast does it flow? What types of soil or rock is present? Is there any barrier, such as a thick claystone, to prevent the contaminants from migrating offsite or to other aquifers? Which way does the wind blow and how often? How far are you from population centers?

How do you conduct a site investigation to identify hazards? As this example shows, the process can be costly and time consuming. It took close to twenty years from the start of investigations to the final signing of the ROD in 1995 at the cost of millions of dollars. Luckily, there are many resources to find out the needed information. EPA has many guidance documents including:

The Remedial Investigation: Site Characterization and Treatability Studies (EPA, 1989) http://www.epa.gov/superfund/policy/remedy/pdfs/93-55301fs2-s.pdf

Principles for Managing Contaminated Sediment Risks at Hazardous Waste Sites (EPA, 2002) http://www.epa.gov/superfund/policy/remedy/pdfs/92-85608-s.pdf

Preparation of Soil Sampling Protocols: Sampling Techniques and Strategies (EPA, 1992)

http://www.epa.gov/swerust1/cat/mason.pdf

Furthermore, there is a large list of EPA documents covering risk assessment at : http://www.epa.gov/oswer/riskassessment/superfund_toxicity.htm

I have one last word on RMA. Okay, two. The site has figured prominently in environmental history and law as several major issues concerning Superfund were settled due to lawsuits concerning RMA (Army v. Shell and Colorado v. Army). Secondly, the site has been greatly cleaned up and is now a national wildlife refuge. Both North Plants and South Plants have been removed and either sent offsite or buried in the massive special landfills just north of the former North Plants area. The area is full of wildlife including bison, deer, and eagles. There is still some contamination in the groundwater, so some risk is present, but nothing like it was.