The purpose of conducting an environmental site assessment is to determine the presence of hazardous materials on a site.The first phase of an environmental site assesment is performed to determine if the possiblity of hazardous materials on the site. Research into a site’s history, physical settings and purpose is used to determine this assessment. When a site is bought or sold, a phase I assesment is necessary to determine what parties are responsible for liabilities and costs of clean up and remediation. This is important to protect the buyer from any future contamination that maybe found as a result of previous owners activities. During a Phase II assessment the presence of contamination is determined through sampling and analysis. This phase is used to determine remediation and clean up of a site.
For this project we studied the Asarco plant in El Paso, TX that was recently closed earlier this year. The history of this site ranges from the production of many types of metal contaminants such as lead, copper, cadium, zinc, chromum and antimony from 1887-1992 at various times throughout this site’s history. This site has come under scrutiny from the EPA for violations of RCRA for allegedly mishandling hazardous waste. With a long history of exposing the environment to metal contaminants an environmental site assement is necessary to determine any liability ASARCO may have for clean up and remediation of this site and the surrounding communities as a result of their companies activities. If the site were to be used for another purpose it is necessary to perform a site assessment to determine those liable to accept clean up and remediation of this site.
Phase I
I Physical Settings, geologic charecteristics, maps, photographs
The aerial map below indicates the ASARCO Smelter Site property. This photo along with the satellite image and the topographical maps help us to understand the contamination area and its surroundings. By viewing these maps we can see man-made structures including roads, stadiums, neighborhoods, and other buildings. We can also see bodies of water and the surface contours which can help us to understand the direction which the contaminants may move. The topographical maps indicate some higher lying areas. Contamination in this area would move to lower areas which may result in contaminants migrating into waterways or neighborhoods.
The soil type and water table level are also indications as to how the contaminants may move. The areas soil is a combination of sediment from surrounding mountains and rivers. The sediment is composed of gravel, sand, silt, and clay and can vary from fine to course. The water table at this site ranges from forty to sixty feet and the aquifers consist of layers of the sediment, boulders, and bedrock. The area also had washes which were filled in using local soil types as well as slag which is a solid waste produced during smeltering. The groundwater seems to follow the path of these washes and moves in a westward direction which allows contaminants to flow toward waterways.
Aerial map indicating the ASARCO property in red. http://www.tceq.state.tx.us/remediation/sites/asarco.html
II Site Reconnaissance
1. Current Use of the Site:
The area is a developed commercial copper mine, founded in 1887 and placed on “care and maintenance status” in 2004 (ASARCO, 2007). In 2005, under direction of the Texas Commission on Environmental Quality (TCEQ), the site has been undergoing remediation activities for heavy metal contaminants (ASARCO, 2007).
2. Prior Use:
Mining operations utilize and form several types of hazardous substances and wastes, using sulfuric acid to dissolve minerals surrounding the copper ore and electrowinning processes to concentrate copper, producing heavy metals in smelting operations and generating tailings containing various hazardous elements. Using a site diagram and following operational knowledge of the mining process, buildings used to store hazardous materials and wastes can be identified. Considering that the site is now inactive it is important to identify the areas that may have been overlooked for waste removal.
3. Hazardous Materials Storage and Use Areas:
Asarco reported to the EPA that it generated 616 tons of RCRA waste in 2007, 75 ton in 2005, 239 tons in 2003 and 2002 tons in 2001 (U.S. Environmental Protection Agency [USEPA], 2008, p. 276; USEPA, 2006, p. 278; USEPA, 2005, p. 296, USEPA, 2003, p. 319). There is a history of hazardous materials and waste on the site, with this knowledge, a site diagram or aerial photograph would be useful in identifying the location of buildings that may have housed these materials and wastes. Additionally, aerial photographs of from a period of time when the mining was running would help in identifying the location of drums and tanks.
III Interviews, Site Map, Report
Phase one site assessments often use interviews to inquire about the types of activities and management of current use. Information gathered during interviews can be included in the environmental site assessment report. Site maps can include site drainage, locations of site structures and potential hazards on-site. The site maps provided by the Texas Commission of Environmental Quality (TCEQ) show the structure locations and the areas of concern regarding contamination. Other maps provided also show the groundwater elevations at the site and potential migration routes or contaminants. A cross sectional map of the contaminated ASARCO site shows points of infiltration and the direction of the plumes a heading. Once an investigation is nearing completion a final report is written. The report lists all significant finding found during the investigation. A report will we address whether the site requires a phase II environmental site assessment or if no further action is required. The ASARCO contamination report stated that there were significant concerns about possible hazards at the El Paso site that required further investigation.
Beyond Phase I
I Release Considerations
The Chemicals of Concern released at this facility, the potential dangers they present to public health, and the concentrations found at this site are:
Arsenic (As): a known human carcinogen can cause vomiting, diarrhea, and numerous other health effects from both short and long-term exposure. Surface soil concentrations of 17,000 mg/kg
Cadmium (Cd): a probable human carcinogen can cause both short term effects such as pulmonary irritation and long term effects such as kidney disease. Surface soil concentrations of 3,500 mg/kg
Chromium (Cr): a known human carcinogen, Chromium causes both short and long term health effects; is much more toxic as Chromium (VI) than as Chromum (III)
Copper (Cu): is an essential human element, but exposure to levels higher than the required level can cause nausea or vomiting in the short term, and can lead to kidney damage over long term exposure.
Iron (Fe): a mineral essential for human health, there are no direct, adverse health effects from the ingestion of iron.
Lead (Pb): a probable human carcinogen, lead exposure can lead to a multitude of health issues such as behavioral or learning problems in children and reproductive issues in adults. Surface soil concentrations of 49,000 mg/kg
Selenium (Se): not classifiable as a carcinogen, short term exposure to selenium can cause fatigue or irritability while long term effects can include liver/kidney disease and damage to the nervous system.
Zinc (Zn): not classifiable as a carcinogen, exposure to zinc can cause numerous short term effects such as nausea and vomiting if ingested, ‘metal plume fever’ if inhaled, or dermatological irritation if applied to the skin. Long term exposure can lead to anemia and has been shown to affect the fertility of rats.
II Physical and Chemical Contaminant Considerations:
Physical and chemical properties of the contaminant will determine its overall mobility. The most critical properties include water solubility, viscosity, specific gravity, soil sorption coefficient, biodegradability index, vapor pressure, and vapor density.
Water solubility determines how easily a contaminant will dissolve in water. Highly soluble contaminants will dissolve readily. The higher the solubility, lower the sorption into the soil.
Viscosity is the resistance of a liquid to shear forces or flow. Viscosity affects the mobility of a contaminant. A highly viscous substance will likely remain in the liquid state and become absorbed into the soil rather than dissolve. It will stay in the unsaturated zone longer than a contaminant with lower viscosity.
Specific gravity is the density of a substance relative to the density of water. Pure water was chosen as the baseline for specific gravity and given the value of 1. Those materials with a specific gravity more than 1 will sink. Those with a specific gravity less than 1 will float.
Soil sorption coefficient is a measure of how tightly a material binds of sticks to soil particles. The greater the value, the less likely a chemical will contribute to runoff. A very high value means it is strongly absorbed onto soil and does not move through out the soil. Biodegradability means that soil microorganisms and natural weathering processes are capable of decomposing the material into recyclable soil nutrients without leaving any harmful residues behind.
Vapor pressure is the pressure exerted by a vapor in equilibrium with its solid or liquid phase. The higher the pressure of a contaminant in the vapor phase, the greater the amount absorbed.
Vapor density is the ratio of the weight of a given volume of one gas to the weight of an equal volume of another gas (usually hydrogen). Vapor density is calculated by taking the mass of n molecules of gas and dividing that by the mass of n molecules of hydrogen. The vapor density of air is 1. A gas with a density greater than one is heavier than air and will stay low to the ground. A material with a vapor density less than 1 will rise and more quickly dissipate in the air. Contaminants with lower molecular weights will move away from the source of contamination over time.
Physical and Chemical Considerations of Site Chemicals Released:
The following chemicals are metals in the solid state. Vapor pressure, density, and viscosity don’t apply to solids. None are soluble in water. The main concerns would be the specific gravity and how each element stays in the soil.
Arsenic (As) (Metal):
Water solubility: insoluble
Specific gravity: 5.72
Cadmium (Cd)
Water solubility: insoluble
Specific gravity: 8.64
Chromium (Cr):
Water solubility: insoluble in water
Specific gravity: 7.14
Copper (Cu):
Water solubility: insoluble in cold water
Specific gravity: 8.94
Iron (Fe):
Water solubility: Insoluble in cold and hot water
Specific gravity: 7.86
Lead (Pb):
Water solubility: insoluble in cold water
Specific gravity: 11.3
Selenium (Se):
Water solubility: insoluble in cold water
Specific gravity: 4.81
Zinc (Zn):
Water solubility: insoluble in hot and cold water
Specific gravity: 7.133
III Site Considerations
A vital part of any site assessment is the determination of the presence and the physical condition of chemical storage tanks. For in place storage tanks this can be simply a detailed visual inspection for evidence of leakage from the tank or its associated plumbing. Above ground storage tanks no longer on-site and underground storage tanks (UST) can provide additional challenges.
Additional resources will be needed in order to determine the integrity of USTs and the location, direction and magnitude of the contaminant plume. There are several technical means available to locate the suspected USTs. These include ground penetrating radar, metal detection and electromagnetic means. The locations of the tanks at the ASARCO site in question are known so these methods will not be necessary.
The ASARCO tanks at this site were known to have had 2 instances of diesel fuel releases totaling nearly 95000 gallons of diesel fuel. Groundwater at the site is in the 40 to 60 depth. This depth decreases to approximately 10 feet nearer the Rio Grande River. The site was constructed on a series of arroyos (gulleys) that were filled with soil and slag produced on site. Because of the filled arroyos ground water flow is typically towards the Rio Grande.
In order to determine the flow rate and direction a series of wells would be the most valuable tool. Due to the greater depth of the groundwater at the site these wells would need to be of the drilled/auger type. As the plume approaches the river and the groundwater is shallower direct push wells would be more cost effective and ultimately excavation could be used to determine levels of contamination.
References:
1) Pichtel, John. (2007).Fundamentals of Site Remediation. Government Institutes, Lanham
2) Cleanup Plans for the American Smelting and Refining Company (ASARCO) Site, El Paso. [Online] Available at www.tceq.state.tx.us/remediation/sites/asarco.html [2009, September 24]
3) Texas Commission on Environmental Quality. (2009, September 24). Cleanup Plans for the American Smelting and Refining Company (ASARCO) Site, El Paso Retrieved October 2, 2009, from http://www.tceq.state.tx.us/remediation/sites/asarco.html
4) Hydrometries, Inc. (1998). ASARCO El Paso Copper Smelter Remedial Investigation Report El Paso, TX. Retrieved October 4, 2009,
5) Texas Commission on Environmental Quality. (2009, September 24). Cleanup Plans for the American Smelting and Refining Company (ASARCO) Site, El Paso Retrieved October 2, 2009, from http://www.tceq.state.tx.us/remediation/sites/asarco.html
6) Environmental Protection Agency chemical listings, found at http://www.epa.gov/. No update date given. Information retrieved on October 4, 2009.
7) Case Studies in Environmental Medicine, Agency for Toxic Substances and Disease Registry, found at http://www.atsdr.cdc.gov/csem/csem.html. Updated July 25, 2009. Information retrieved on October 4, 2009.
8) Cleanup Plans for the American Smelting and Refining Company (ASARCO) Site, El Paso, The Texas Commission on Environmental Quality, found at http://www.tceq.state.tx.us/remediation/sites/asarco.html. Updated September 1, 2009. Information retrieved on October 4, 2009.
9) Texas Comission on Environmental Quality. (2009, September 24). Cleanup Plans for the American Smelting and Refining Company (ASARCO) Site, El Paso . Retrieved October 3, 2009, from Texas Comission on Environmental Quality: http://www.tceq.state.tx.us/remediation/sites/asarco.html
10) EPA. (2009, July 21). Expedited Site Assessment Tools For Underground Storage Tank Sites: A Guide For Regulators. Retrieved October 3, 2009, from Underground Storage Tanks: http://www.epa.gov/swerust1/pubs/sam.htm
11) U.S. Environmental Protection Agency. (2008). The National Biennial RCRA Hazardous Waste Report (2007 ed.) (EPA530-R-08-014). Washington, DC: U.S. Government Printing Office. Retrieved October 4, 2009 from the World Wide Web: http://www.epa.gov/waste/inforesources/data/br07/list07.pdf.
12) U.S. Environmental Protection Agency. (2006). The National Biennial RCRA Hazardous Waste Report (2005 ed.) (EPA530-R-06-008). Washington, DC: U.S. Government Printing Office. Retrieved October 4, 2009 from the World Wide Web: http://www.epa.gov/waste/inforesources/data/br05/list05.pdf.
13) U.S. Environmental Protection Agency. (2005). The National Biennial RCRA Hazardous Waste Report (2003 ed.) (EPA530-R-03-009). Washington, DC: U.S. Government Printing Office. Retrieved October 4, 2009 from the World Wide Web: http://www.epa.gov/waste/inforesources/data/br03/site03.pdf.
14) U.S. Environmental Protection Agency. (2003). The National Biennial RCRA Hazardous Waste Report (2001 ed.) (EPA530-R-03-009). Washington, DC: U.S. Government Printing Office. Retrieved October 4, 2009 from the World Wide Web: http://www.epa.gov/waste/inforesources/data/brs01/list01.pdf.
15) http://www.webelements.com/
16) http://www.sciencelab.com/
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