MTBE Clean-up Status in South Lake Tahoe
Todd A. Lenkin
American River College, Geography 350: Data Acquisition in GIS; Fall, 2009
Contact Information: 3000 Camino Heights Dr, Camino, CA 95709
(530) 417-1443; tlenkin@yahoo.com
Abstract
An additive to gasoline known as methyl tertiary-butyl ether (MTBE), used to help improve air quality, has had adverse impacts on groundwater. Primarily due to leaking underground storage tanks, many contaminated sites have been identified and are undergoing clean-up efforts. In South Lake Tahoe, a landmark lawsuit was settled in 2002 in the amount of sixty-nine millon dollars paid to the water district by the defendants.
Using data obtained from the state's online GIS called Geotracker and inputing the data into ArcMap, I will look at the status of the clean-up efforts in South Lake Tahoe. I will also critique the effectiveness of the public portal in its ability to provide useful and accurate information to the layperson.
Introduction
MTBE (methyl tertiary-butyl ether) is a man-made gasoline additive that has become a environmental catastrophe. In the mid 1990's, to meet the oxygenate requirement provisions of the Clean Air Act, MTBE became the oxygenate of choice for the oil industry. Oil companies spent billions of dollars to produce it. Oxygenates make gasoline burn more completely and therefore, reduce harmful air emissions. However, MTBE has two physiochemical characteristics that threaten groundwater resources. The first is its high water solubility. It has easily found its way into public and private water supplies from leaking storage tanks, spills and other leaks. The unpleasant taste and odor of MTBE can be detected at very low levels in drinking water. It is described as being turpentine-like. Studies conclude that consumers can detect it as low as 15 parts per billion (ppb). It is also considered a "possible human carcinogen" by EPA but little is know about the long-term effects. The second is its relative resistance to biological degradation in the subsurface. This means that clean up is very challenging and will be with us for many years to come.
In South Lake Tahoe, MTBE has been responsible for closure of 13 of STPUD's drinking water wells and prompted a landmark lawsuit settled in August of 2002, with settlements of over $69 million paid to the District. Leaking underground storage tanks (LUST) were the cause for the contamination. The area of concern has also been delineated as hydrogeologically vulnerable, so the recalcitrant nature of MTBE is particularly troublesome.
Geotracker is the State Water Board database and GIS that provides online access to environmental data. By obtaining data on LUSTs and results of water sampling for MTBE, I will determine the status of the clean up efforts in South Lake Tahoe. I will also analyze the performance of the portal in its quest to provide meaningful and useful information to the public.
Background
Since the introduction of MTBE to raise gasoline octane in the late 1970s, MTBE usage in the U.S. has grown rapidly. The usage has also been fueled by FCAA (Federal Clean Air Act) requirements which mandate oxygenated gasoline during the wintertime to help meet standards for Carbon Monoxide (MTBE Briefing Paper, Cal EPA, 1997). Hailed in the early 1990s as a toxic-busting additive that halved the level of cancer-causing benzene in vehicle exhaust, MTBE soon earned a reputation as a nasty water pollutant (Nancy Vogel, The Sac Bee, 1998). Thousands of gallons of MTBE are leaking from underground gas storage tanks, threatening the nation's water supply (Susan Sward, San Francisco Chronicle, 1998). MTBE is of concern because it is more soluble in water than the traditional gasoline components. Because of this characteristic, it moves readily to groundwater and can be present in higher concentrations than the traditional compounds (Kip Wiley, Does California Need MTBE?, 1998). A second physiochemical characteristic of MTBE is its relative resistance to biological degradation in the subsurface (Brett Wyckoff, SWRCB MTBE Groundwater Information Sheet, 2002).
The El Dorado County Board of Supervisors adopted Resolution Number 263-98 on the 20th of October, 1998 declaring El Dorado County a MTBE Free Zone. They specified numerous concerns such as the USGS finding detectable levels of MTBE in Lake Tahoe to a depth of 90 feet, the fact that it would take less than a teaspoon of gasoline to contaminate a 10,000 gallon swimming pool to a level of 14 ppb of MTBE (California Office of Environmental Health Hazards Assessment proposed public health goal) and that the South Tahoe Public Utilities District (STPUD) are shutting down their drinking water wells because of MTBE contamination.
On the 28th of March, 2000, Ordinance Number 4553 was passed and adopted by the Board of Supervisors of the County of El Dorado prohibiting the sale of fuel containing MTBE in the Lake Tahoe Basin. The USGS has delineated the Tahoe Valley South Basin as a potentially rapid infiltration zone and a hydrogeologically vulnerable area to groundwater contamination. The Lake Tahoe Region (LTR) was designated a "national concern" under Presidential Order #13057 (Clinton, 1997), citing its "extraordinary natural, recreational, and ecological resources." Since 1997, MTBE has been responsible for closure of 13 of the District's drinking water wells and prompted a landmark lawsuit (South Tahoe Public Utility District vs. ARCO et al) settled in August 2002, with settlements of over $69 million paid to the District by defendants.
The California Department of Health Services (DHS) regulates MTBE as a drinking water contaminant. Since 1997, when DHS regulations identified MTBE as an unregulated chemical requiring monitoring, public water systems have analyzed their water for its presence. Underground storage tanks make up the majority of the releases (Brett Wyckoff, SWRCB MTBE Groundwater Information Sheet). In February of 1997, California Assembly Bill 592 and Senate Bill 1189 were introduced to determine the feasibility of creating a Statewide geographical information system (GIS) to assess the vulnerability of public drinking water sources from fuel hydrocarbon releases and to assist in managing the public health risk that may be associated with these releases. These bills were introduced following the contamination with the fuel additive MTBE and subsequent closure of drinking water wells supplying the City of Santa Monica, and with the realization that leaking underground fuel tanks (LUFTs) may threaten other drinking water wells throughout the state (D.L Drogos, Exploring the Environmental Issues of Mobile, Recalcitrant Compounds in Gasoline, 2000).
In Arkansas, the Department of Environmental Quality, Regulated Storage Tank Division received a EPA Region VI grant to map LUST sites. They used ESRI software to study the impact of petroleum contamination on a public water system in Dardanelle (Donald Fiegel, GIS Tools for Remediation of Groundwater). In the Mid-Atlantic States, EPA Region III formed a workgroup to investigate the impact of MTBE in Virginia (Jack Hwang, Report on The Mid-Atlantic States' MTBE Pilot Project, 2004). They used public water supply sampling, GIS plotting of UST and LUST sites and public drinking water wells and development of a ranking tool. And for the city of Temecula in California, where severe MTBE contamination was found, ArcGIS and Geotracker were utilized to explore, analyze and autocorrelate MTBE concentration data to create maps that would predict groundwater contamination (Jie Y. He, ARCGIS Geostatistical Analyst Application in Assessment of MTBE Contamination). In the United Kingdom, a study was done to evaluate the risk of MTBE to urban groundwater for the city of Nottingham using a risk-based prediction tool developed with Arc View GIS (Brenda Chisala, Evaluating the Risk of MTBE to Urban Groundwater, 2004).
Methods
Geotracker, the state's public web portal, is a database and GIS that provides online access to environmental data. The regulatory information for the LUST sites includes the locational data of the monitoring wells and its corresponding water sampling for contaminates, including MTBE. What I intend to do is look at how the site presents the information online and then download the data and see if I can recreate the results and perhaps improve on the presentation.
Results
Using the map viewer in Geotracker, I first zoomed to my subject area, South Lake Tahoe, and selected to view the LUST sites and the monitoring well locations. I copied the list of the LUST sites which included the name, global id, clean-up status and the address.
I downloaded two files from Geotracker. One was the monitoring well locations and the other was the water sampling results. Both were only available in .txt format. I had to get all the locations for the county and all the contaminate sampling - no option to filter. First I opened the files in Notepad and edited the files to include only the data I needed. Because the data wasn't in a consistent form, this proved to be very time consuming. I only kept the locations that were in my study area and only sites that had MTBE sampling results above reportable levels. Once I reduced the data to a workable size and content, then I was able to open it in a spreadsheet.
The unique identifier for the LUST site is the global id. The well location id's were only unique to each site. So this required me to concatenate the two fields to link the sampling data to each well. I obtained the actual name of the LUST site and its address and cleanup status from the list that I copied from the screen.
Using ARC Catalog, I created a shapefile of the well locations. Then with ARC Explorer, I first displayed the well locations along with a previously created layer of underground storage tank locations made with Google Earth.
There was no way to relate the table of sampling data using ARC Explorer. Data could be displayed on the screen from the spatial object's attribute table, but that wouldn't suffice for what I was trying to show - the change over time of MTBE contamination for a group of monitoring wells.
I then made a file geodatabase and moved the new created shapefile and also the spreadsheet of the MTBE sampling data into a basemap already created that included the location of hazardous material sites in El Dorado County. I also added the NAIP layer for the county and made the orthoimagery viewable when the scale was zoomed in to 1:10,000. I also added a layer of wetlands obtained from the county's GIS Library.
The first thing that stood out is the location of a well in the lake. This led me to check all the locations to find any errors by looking at site maps found on Geotracker. One location proved to be about a half-mile off. I exported the site map of Fox Gas and then georeferenced it into the base map and then I created a new layer with the correct locations of the wells.
Now with the locations verified and data corrected and formated, I was ready to look at the MTBE contamination spatially and temporally. Using a geodatabase allowed me to relate the well locations with the sampling data. I was able to select the wells by LUST site, relate to the MTBE sampling data, and then create graphs that showed the amount of MTBE detected over time.
This is a representation of a few different patterns that emerged. Clearly, the intersection of Ski Run Boulevard and Lake Tahoe Boulevard had the highest amount of contamination but it shows that the remediation efforts have had some success in reducing it. During 2004, Al's Chevron Station had sampled for MTBE at over 65,000 ppb but a gradual lowering has occurred. It still remains very high over the primary goal of thirteen ppb. The Tahoe Keys Marina shows a much better picture. Initial rates were nearly ten times over the allowable limit, but for the last five years or so, MTBE is non-detectable. Good news considering the proximity of the location to wetlands. USA Gas, on the other hand, remains an enigma. MTBE detection has been fluctuating back and forth ever since sampling began, almost seasonally.
Analysis
Downloading the data from Geotracker and inputing into ARC View proved to be a worthwhile endeavor. Although the format the data was obtained in was somewhat tedious to work with, it was workable and enabled me to organize it in a more useful form. Flexibility was gained to manipulate the data to satisfy my own curiousity. During the process, I discovered that the data had some errors that I was able to correct. I also found that some the data submitted to the site was not always in the required format, which led me to initially be missing data. In scaling down the data, there were lines that were deleted in error because it had an extra field that didn't belong. In other cases, there was clearly data that was not reported or downloaded to the site as required by the regulator. Redwood Oil is a case where scanned reports showed sampling for the last few years that was not included as part of the download available.
In the case of Swiss Mart Station on Emerald Bay Road, the responsible party had refused to cooperate with the regulator and clean-up never began, so data was never obtained. The water board could have imposed a penalty of more than $4 million under state law, but recommended a penalty of $460,300. The case was just decided in court and a penalty was ordered in the amount of $222,000.
Thoroughness and accuracy of the data could only be determined by reviewing the cases individually. Out of the numerous contaminated sites reported in Geotracker, numbering in the hundreds for the South Lake Tahoe area, there were approximately fifteen that had MTBE sampling data that was over the reportable limit of 5 ppb. Nearly ten of those sites still remain as open cases. The remediation taking place has had a noticeable improvement in the majority of the sites, but a handful of cases still remain with unknown predictions of closure status.
Trying to obtain a spatial and temporal picture of MTBE contamination in South Lake Tahoe by only using Geotracker tools was difficult. Provided is a means to filter for MTBE for maximum concentrations, but it could only be viewed on an individual well basis. In the following screen shot, I couldn't zoom in enough to place the cursor on the well that had the highest sampling result. I was able to determine the well where the maximum concentration was detected by viewing a report.
To get an idea of the sampling over time, I had to go to another website associated with Geotracker. It did take some searching to find it, as its function was not clearly established. GeoTracker GAMA (Groundwater Ambient Monitoring and Assessment) displays the sampling for particular contaminates and plots the results on a graph over time, but the wells are grouped together and their locations are generalized. In California, the location of drinking water wells are not made public due to security concerns. And sampling of private water wells are not required. One may obtain a generalized idea of potential threats to drinking water, but in order to know for sure, it is the owner's responsibility to do sampling.
Conclusion
MTBE is a prime example of a man-made substance being created and subsequently finding its way into the natural environment with dire consequences. It's ironic that something that was used to help reduce the airborne contaminants from vehicle exhaust led to extensive groundwater contamination. The sad thing is that the chemical's characteristics of being highly water soluble and very resistant to biodegration underground were well known facts, along with the reality that the underground storage tanks were known to leak. The legacy of MTBE usage is with us for years to come. The silver lining was that the situation got so bad that, at least in California, UST requirements were "beefed up," requiring such things as monitoring systems and double-walled tanks with secondary containment. Leaks and spills still occur, but at least we're getting a better control of it.
MTBE is no longer used in California. In fact, there have always been better alternatives to make gasoline burn more clean that are more effective. The contamination that we live with caused by the fuel that powers our vehicles is most visible in the air. In attempting to solve the smog problem that makes it unhealthy to breath the air, we created another that is not so visible. The water that we drink has been made undrinkable.
There are many lessons to learn from this debacle. The state mandated public portal on the internet fulfills its responsibility by providing the data on the contamination of our groundwater, but the picture that is portrayed does not seem alarming. Data on it's own isn't so exciting. View it on a map and over time and it gets a little more interesting. Linked to stories and case studies and the data comes alive. The biggest lesson: We have a responsibility to clean-up the mess that we created as we have not only polluted the natural environment, we have threatened the health of mankind.
References
California Environmental Protection Agency, 1997. MTBE Briefing Paper.
Chisala, Brenda N. & Nigel G. Tait & David N. Lerner, 2004. Hydrology: Science & Practice for the 21st Century, Volume II. Evaluating the Risk of Methyl Tertiary-Butyl Ether (MTBE) to Urban Groundwater.
Drogos, D.L. & A.F. Diaz, 2000. American Chemical Society. Preprints of Extended Abstracts, Volume 40, Number 1. Exploring the Environmental Issues of Mobile, Recalcitrant Compounds in Gasoline.
Feigel, Donald. Arkansas Department of Environmental Quality. GIS Tools for Remediation of Groundwater.
He, Jie Y. & Xudong Jia; ArcGIS Geostatistical Analyst Application in Assessment of MTBE Contamination.
Hwang, Jack, 2004. U.S. Environmental Protection Agency, Mid-Atlantic Region. Report on The Mid-Atlantic States' MTBE Pilot Project.
Jensen, Adam, 2009. Tahoe Daily Tribune. Gas Station Operator Fined for Spill.
South Tahoe Public Utility District, 2002-08; MTBE FAQ's.
Sward, Susan, 1998. San Francisco Chronicle. State OKs Sale of Gas Without MTBE Additive - Chemical Reportedly Poisons Water Supply.
Vogel, Nancy, 2008. The Sacramento Bee. Fuel-Additive Rules Relaxed: But Capital Stuck with MTBE.
Wiley, Kip, 1998. Does California Need MTBE?
Wyckoff, Brett, 2002. SWRCB-Division of Clean Water Programs, Groundwater Special Studies Unit. MTBE Groundwater Information Sheet.
