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IDENTIFICATION AND MAPPING OF POTENTIAL GROUND WATER CONTAMINATION

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IDENTIFICATION AND MAPPING OF POTENTIAL GROUND WATER CONTAMINATION ...

IDENTIFICATION AND MAPPING OF POTENTIAL GROUNDWATER

    CONTAMINATION SOURCES IN URBAN TECATE

PROJECT NUMBER: W-04-04

KATHERINE COMER, SAN DIEGO STATE UNIVERSITY

    JOSÉ LUIS FERMÁN, UNIVERSIDAD AUTÓNOMA DE BAJA CALIFORNIA

    NARRATIVE SUMMARY Water resources in the Tecate region are under threat (Castro Ruiz 2002; Holsher 2005;

    Forster 2005). Wells are being contaminated, and half the wells operated by the State Public

    Services Commission of Tecate (CESPTE, Comisión Estatal de Servicios Públicos de Tecate)

    are dry, forcing Tecate to increase its imported water from 20% of total usage in 1999, to 80%

    of the total usage in 2005. Urban streams rarely flow, and testing indicates high pollution

    levels (Lozano 1995; Gersberg et al. 2000; Luderitz et al. 2005; CESPTE unpublished).

    However, Tecate still is able to use groundwater to meet around 10% of its demand. Proper

    planning and protection of the aquifer and wellheads could stabilize the downward trend for

    Tecate’s groundwater quality and quantity.

This interdisciplinary one-year field project involved a team of researchers from San Diego

    State University (SDSU) and the Autonomous University of Baja California (UABC,

    Universidad Autónoma de Baja California). The goal of the project was to create a data

    storage and analysis tool for groundwater and surface water resources in Tecate, Baja

    California. The project converted existing spatial and non-spatial data into a high-resolution

    Geographic Information System (GIS), for ease of use by agencies, researchers, and the

    public. Researchers trained the client, CESTPE, on the use of the GIS, and the client also

    received access to tabular data in a non-GIS format. The client will use the database to plan

    for future water services in the community and for improving wellhead protection and

    monitoring programs.

The project also inventoried potential sources of groundwater and surface water

    contamination in Tecate using the California Department of Health Services Possible

    Contaminating Activities (PCA) Inventory for Ground Water (CADWSAP 2003). However, the

    PCA categories and risk levels were not totally appropriate for Tecate, Baja California.

    Therefore, the researchers modified the checklist according to suggestions from Helperin et al.

    (2001) and local CESPTE experts to more accurately describe the potential level of

    contamination to the groundwater in Tecate. This exercise was also useful in determining if a

    binational checklist could be created that might aid managers implementing binational

    pollution prevention programs. Researchers collected GPS locations of PCAs in the field and

    subjectively rated their risk to groundwater resources utilizing California’s PCA risk classes

    combined with expert opinion from CESPTE personnel.

    The project’s products are packaged in a GIS project which is accompanied by bilingual

metadata found on http://trw.sdsu.edu/English/GIS/InterMaps/ims/website/

    tecateGWpublic/viewer.htm. All shapefiles were provided to CESPTE and the Municipal

    Department of Urban Administration (DAU), and are also available at

    http://trw.sdsu.edu/English/GIS/GISDownloads/tecateDataDownloads.htm. An online

    version of the project was published using ESRI’s ArcIMS 9.0 available at

    http://trw.sdsu.edu/English/GIS/InterMaps/ims/website/tecateGWpublic/viewer.htm. With

    this tool, users can display data, query the attribute tables, and design basic maps.

    Bilingual metadata webpages accompany each layer.

Using the GIS database, the research team came to the following basic conclusions

    about Tecate’s groundwater. These issues deserve further investigation by Mexican

    authorities and well owners:

    ? 13 PCAs of very high and high risk occur over or within 200 meters of the aquifer.

    ? 48 wells are at risk of contamination by very high and high risk PCAs. If one of

    these PCAs should emit contamination, it would take approximately two years to

    reach the wellhead (274 m buffer assuming a fractured rock aquifer). Assuming a

    porous aquifer, there are 41 wells at risk. Most of these are CESPTE wells used for

    potable water and were active in 1999.

    ? Tecate wells appear to be at high risk.

    ? Tecate’s high-density residential, industrial, and commercial land uses around the

    aquifer and wells do not appear to be compatible with wellhead protection.

    2

IDENTIFICATION AND MAPPING OF POTENTIAL GROUNDWATER

    CONTAMINATION SOURCES IN URBAN TECATE

    PROJECT NUMBER: W-04-04

KATHERINE COMER, SAN DIEGO STATE UNIVERSITY

    JOSÉ LUIS FERMÁN, UNIVERSIDAD AUTÓNOMA DE BAJA CALIFORNIA

INTRODUCTION

    Water resources in the Tecate region are under threat (Castro Ruiz 2002; Holsher 2005;

    Forster 2005). Wells are being contaminated, and half the wells operated by the State Public

    Services Commission of Tecate (CESPTE, Comisión Estatal de Servicios Públicos de Tecate)

    are dry, forcing Tecate to increase its imported water from 20% of total usage in 1999, to 80%

    of the total usage in 2005. Urban streams rarely flow, and testing indicates high pollution

    levels (Lozano 1995; Gersberg et al. 2000; Luderitz et al. 2005; CESPTE unpublished).

    However, Tecate still is able to use groundwater to meet around 10% of its demand. Proper

    planning and protection of the aquifer and wellheads could stabilize the downward trend for

    Tecate’s groundwater quality and quantity.

This interdisciplinary one-year field project involved a team of researchers from San Diego

    State University (SDSU) and the Autonomous University of Baja California (UABC,

    Universidad Autónoma de Baja California). The goal of the project was to create a data

    storage and analysis tool for groundwater and surface water resources in Tecate, Baja

    California. The project converted existing spatial and non-spatial data into a high-resolution

    Geographic Information System (GIS), for ease of use by agencies, researchers, and the

    public. Researchers trained the client, CESTPE, on the use of the GIS, and the client also

    received access to tabular data in a non-GIS format. The client will use the database to plan

    for future water services in the community and for improving wellhead protection and

    monitoring programs.

The project also inventoried potential sources of groundwater and surface water

    contamination in Tecate using the California Department of Health Services Possible

    Contaminating Activities (PCA) Inventory for Ground Water (CADWSAP 2003). However, the

    PCA categories and risk levels were not totally appropriate for Tecate, Baja California.

    Therefore, the researchers modified the checklist according to suggestions from Helperin et al.

    (2001) and local CESPTE experts to more accurately describe the potential level of

    contamination to the groundwater in Tecate. This exercise was also useful in determining if a

    binational checklist could be created that might aid managers implementing binational

    pollution prevention programs. Researchers collected GPS locations of PCAs in the field and

    subjectively rated their risk to groundwater resources utilizing California’s PCA risk classes

    combined with expert opinion from CESPTE personnel.

The project’s products are packaged in a GIS project, which includes the following layers, all

    3

    of which are accompanied by bilingual metadata found on http://trw.sdsu.edu/English/GIS/

    InterMaps/ims/website/tecateGWpublic/viewer.htm:

    1. An aerial photograph flown by NOAA in 2000 at a scale of 1:24,000. The series was

    mosaiced using ERDAS Imagine software by Dave McKenzy from the CESAR Lab at

    SDSU in 2004. Other layers were digitized against this high-resolution base layer. 2. A land use map from the year 2000 was created at a scale of 1:24,000, which borrows

    from existing AutoCAD layers of land use from previous years provided by the

    Municipality of Tecate. Fieldwork and expert opinion was used to verify the map circa

    2000.

    3. Point data on 144 wells in the study area were linked to tabular well data, which was

    provided by Mexico’s National Water Commission (CNA, Comisión Nacional del Agua),

    CESPTE, Tecate’s largest industry the Tecate Brewery, and University of Utah

    research (Forster 2005; Holsher 2005). The tabular data contain data on the physical

    characteristics and uses of the wells, along with a time series of monthly pumping rates.

    Data may be added in Microsoft Excel and linked to the GIS.

    4. Within the 200-meter buffer zone on either side of the river, possible contaminating

    activities (PCAs) to groundwater were mapped with GPS and ranked with CESPTE

    expert opinion according to their threat: very high, high, medium, and low. 5. GIS was used to create concentric rings around each well, delineating the area where

    PCAs might be able to travel through the substrate to a wellhead in approximately two

    years. The default distance used was 187 meters for a two-year travel time, assuming

    a porous aquifer, and 274 meters, assuming a fractured rock aquifer. The rings are

    circular by default, although this may not reflect the true nature of the zone of risk. 6. The researchers digitized the estimated extent of the Tecate porous-sand aquifer in

    2004 as described by hydrogeologist Dr. Craig Forster, University of Utah, who worked

    in Tecate in 2004 (Forster 2005). This digitization was buffered by 200 meters in the

    GIS.

    7. The researchers digitized the estimated maximum extent of the granite bedrock aquifer

    as estimated by researchers at the University of Utah (2004). This extent is the 600

    meters above sea level (m.a.s.l.) contour line, within which bedrock can be seen above

    ground. This boundary represents an extent where CESPTE might look for new well

    locations in the bedrock fractures.

    8. The neighborhoods not serviced by sewage connection in 2004 were digitized as

    described by personnel at CESPTE.

    9. The Tecate River in 2000 was digitized.

    10. Previously collected GIS shapefiles on vegetation were included in the GIS.

    11. Soils

    12. The Tecate River

    13. Streams

    14. Roads

    15. Railroads

    16. The international border

    All shapefiles were provided to CESPTE and the Municipal Department of Urban

    Administration (DAU), and are also available at http://trw.sdsu.edu/English/GIS/

    GISDownloads/tecateDataDownloads.htm. An online version of the project was published

    4

using ESRI’s ArcIMS 9.0 available at http://trw.sdsu.edu/English/GIS/InterMaps/ims/

    website/tecateGWpublic/viewer.htm. With this tool, users can display data, query the attribute

    tables, and design basic maps. Bilingual metadata web pages accompany each layer.

    CONCLUSIONS Using the GIS database, the research team came to the following basic conclusions about

    Tecate’s groundwater. These issues deserve further investigation by Mexican authorities and

    well owners.

    ? 13 PCAs of very high and high risk occur over or within 200 meters of the aquifer.

    ? 48 wells are at risk of contamination by very high and high risk PCAs. If one of these

    PCAs should emit contamination, it would take approximately two years to reach the

    wellhead (274 m buffer assuming a fractured rock aquifer). Assuming a porous aquifer,

    there are 41 wells at risk. Most of these are CESPTE wells used for potable water and

    were active in 1999.

    ? Tecate wells appear to be at high risk.

    ? Tecate’s high-density residential, industrial, and commercial land uses around the

    aquifer and wells do not appear to be compatible with wellhead protection.

R

    ECOMMENDATIONS

    ? Future land use zoning should protect the eastern wellheads that are not yet

    urbanized.

    ? Improve the well monitoring program and start an aquifer-monitoring program to obtain

    conclusive results on groundwater quality.

    ? Collaborate with the Mexican Federal Attorney General for Environmental Protection

    (PROFEPA, Procuraduría Federal de Protección al Ambiente), on future PCA surveys.

    The combination of an outside academic, an authority, and the local surveyor with local

    knowledge would all add value to the results and increase the likelihood of action on

    the part of the government.

    ? Collaborate with Mexico on a cost-benefit analysis of a comprehensive conversion of

    AutoCAD files to GIS along the U.S.-Mexican border.

F

    UTURE RESEARCH QUESTIONS

    This project’s goal was to provide the client with a water resources data clearinghouse and

    analysis tool, not to perform the actual analysis. Some questions that the client could

    investigate using this GIS package are:

    ? Are there spatial or temporal trends in the decline of groundwater levels?

    ? Are there gaps in water quality testing spatially or temporally?

    ? Are there spatial and temporal trends in groundwater quantity, or well levels?

    ? Is there a correlation between trends in groundwater levels and groundwater quality?

    ? Which wells should be protected first, based upon depth, risk of contamination, water

    quality, pumping rates, and water levels?

    ? How much land area runs off into each wellhead, and what are the land use classes?

    ? Which wells are most at risk from nonpoint sources such as storm water runoff?

    ? Where are CESPTE’s most promising sources of clean well water, and how can land

    use zoning be changed to protect those wells from contamination? How would Baja California’s wellhead protection programs compare to California’s programs,

    5

and could a binational solution be implemented? For example, California’s leading causes of

    groundwater contamination are: leaking underground storage tanks, natural sources,

    agriculture, landfills, septic seepage, and industrial point sources (Helperin 2001).

    DISCUSSION Some researchers may be interested in the “lessons learned” from working with a binational team, combining data from several sources, using several mapping tools, and applying United States standards to a Mexican context. The following paragraphs address some of the issues the researchers encountered, and may help other researchers along the U.S.-Mexican border.

    The binational aspect added to the complexity of the project. For example, Mexico generally uses AutoCAD maps. These are drawings in an electronic format regularly used by engineers, and in this case, the maps were out of date and had errors. However, the researchers found them useful as drafts. Experts were familiar with them and felt comfortable correcting them. When the drawings converted to GIS, they significantly sped up the GIS digitization process. The conversion of AutoCAD files to shapefiles has not been used extensively in this area of the U.S.-Mexican border, probably because it is time consuming and can produce errors. However, it is a one-time task. Complete conversion of AutoCAD files to GIS is an option that should be explored along the U.S.-Mexican border. A cost-benefit analysis of the investments in costs and labor should be analyzed against potential technological gains and human capacity building before such a large-scale project begins.

    The original AutoCAD land use map varied in scale. The researchers were unwilling to discard the detailed block level land use information provided near the U.S. port of entry and central plaza of Tecate. However, for future border efforts, the researchers recommend scaling down to create a uniform working scale.

    The researchers did scale up with the land use classifications, and recommend this approach for regional studies. The intention for the land use map was to potentially apply it border-wide, and possibly binationally. The researchers discussed using land use classes such as the original AutoCAD land use scheme, with 15 classes, the Tijuana River Watershed scheme (SDSU and COELF 2005) with about 15 classes, or the San Diego-Tijuana Border Planning Atlas (IRSC 2000) with 8 classes. The researchers chose to use the Border Planning Atlas’

    scheme because it is binational, had a similar scale and extent, and because Tijuana, Baja California, San Diego, California, and Tecate, Baja California are rapidly merging. Three land use classes were not present in Tecate; therefore only five land use classes were used. Scaling up inevitably resulted in a loss of detailed information, as discussed above. The downfall of generalizing with five classes may be that municipal governments in Tecate find it difficult to monitor subtle land use changes during their short three-year administrations. However, using fewer classes created a map that is easier to interpret by a wider range of stakeholders, and its general natural also results in higher confidence in the data.

    Another issue is data integration from different years and scales. This problem was partially addressed by verifying that 1994 data from the Tijuana River Watershed project was consistent with the 2000 photo. However, the scale of the 1994 layers was 1:50,000, and

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    therefore lacks the detail of layers digitized using the 1:24,000 NOAA photo mosaic. This problem may be addressed in future efforts by redigitizing the 1994 layers.

Contrary to the researchers’ expectations, the online version of the project available through

    ArcIMS was not seen as valuable, according to the user surveys administered after the GIS training sessions. Once users were trained on the Arc GIS 9.0 software that allows much more analysis and data manipulation, the online package was less attractive. Since the training sessions occurred in 2004, CESPTE has reported consulting the attribute tables in Arc GIS for the creation of CNA reports, and for calculating the distance between wells.

    An interesting concern about public access to sensitive data arose during this project. The clients requested that the names of the PCAs not be made available to the public. There maybe several reasons for this that could apply in other binational situations. The freedom of information law (Ley Federal de Transparencia y Acceso a la Información Pública Gubernamental) is relatively new in Mexico. Pollution prevention, as practiced in the United States, necessarily requires the identification of potentially contaminating activities before they harm the environment. In Mexico, this idea has not spread widely and therefore may lead people to believe the inventory identifies actual polluters. Finally, environmental enforcement is more vigilant in California than in Mexico; therefore, the public may assume the PCAs on the list are and will continue to make their environment unsafe without consequences. Another concern of the client is that well production rates be kept internally because they are used to set water prices. Based on these two concerns, the researchers created a public version of the IMS project that excluded business names and well production rates. The researchers strongly encourage researchers working in Mexico to respect the client’s wishes

    in terms of publishing sensitive data on the internet. Due to the researchers discreetness, they had access to much more data and other information. The researchers feel that through respect of cultural boundaries, more can be contributed to science and conservation than lost.

    The Tecate fire department and CESPTE personnel volunteered to accompany the researchers through Tecate’s river communities to ensure the researchers’ safety. Their

    presence was helpful for more than just security. Their knowledge of the individual businesses and clandestine dumping practices added great value to the PCA inventory. For example, known polluters were not obvious to the researchers because they dump materials at night. However, local surveyors may have trouble with objective surveying of these dumping practices because of political concerns or fear of retribution, as seen in other monitoring efforts in Mexico. This research exemplifies the value of combining local and non-local survey teams; indeed, the survey would not have been possible without local collaboration. A suggestion for future surveys is to create a local checklist specifically for Tecate, as has been done with this project, and collaborate with an authority such as PROFEPA on the survey. The combination of an outside academic, an authority, and the local surveyor would all add value to the results and increase the likelihood of action on the part of the government.

    There have been complaints about the California PCA checklist (Helperin et. al. 2001). These include:

    1. The magnitude of the threats is not conveyed, as PCAs are grouped by category;

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    2. The program only records whether each category of PCA is represented in a given

    area, without any quantification of the number of the individual sources from each

    category that are present or their sizes;

    3. The reporting is intentionally general and does not identify the potential sources of

    contaminants;

    4. The program focuses on individual wells rather than on the watershed as a whole; even

    in the context of individual wells, the full recharge areas for the wells at issue are not

    assessed;

    5. The California Department of Health Services lacks the authority to take action based

    on its findings. As a result, once an assessment is completed, the department cannot

    respond effectively to the potential threats.

The researchers found that the list does not apply to Tecate’s unique PCAs. Considering the

    abovementioned shortcomings, the researchers made some modifications, and ended up

    with a “Tecate PCA checklist”. The exercise of modifying the California list for use in Baja

    California was useful for testing whether a binational checklist could be created elsewhere

    along the border. To address Helperin et al. (2001), the researchers first conveyed the

    magnitude of risk for each point, not each category. To address the second concern, the

    researchers reported each and every PCA. For the third concern, any and all potential

    contaminating activities were identified. To address the fourth concern, the researchers

    recommended that authorities such as PROFEPA accompany future surveys. For the fifth

    concern, future research may perform the survey at the subbasin scale.

The researchers’ concern that California’s PCAs are not entirely appropriate in Mexico

    resulted in major modifications of the PCA categories. Examples of PCA categories on the

    California list that were retained in the study are: automobile body shops, gas stations,

    landfills, grazing, sand mining, and medical offices. As mentioned before, the researchers

    modified California’s default risk classifications by assigning a risk to each and every PCA,

    depending on the individual source location and size, and expert opinion. For example, storm

    drains were reclassified from medium to high in some parts of Tecate because of the reported

    practice of using them for discharging commercial and household waste. On the contrary,

    lumber processing was classified lower in Tecate because they are small operations that only

    discharge sawdust, and do not use chemical treatments as is common in California.

    Examples of potential sources that did not exist on the California list and were added to the

    Tecate PCA checklist were: illegal dumping, water pipelines, car dumps, car washes, drinking

    water treatment plants, truck parking, terra cota kilns, terra cota factories that paint their

    products, tire sales, cardboard recyclers, public wastewater treatment plants, recreational

    fields, auto parts stores (because auto maintenance is often performed in the parking lots),

    animal lots, latrines not connected to septic tanks, manholes that could burst, chicken

    slaughterhouses, plant nurseries which use chemicals, and laundry mats. In general, the

    researchers think the Tecate checklist is most useful for Tecate authorities and river park

    efforts, and recommend such local modifications depending on the objective of the study.

    Because of the stark differences in practices between Baja California and California, creating

    a binational checklist may not be feasible. As in all such surveys, the surveyor uses qualitative

    judgments, and there is the potential for error.

    8

    Despite pitfalls, the researchers recommend PCA checklists for the U.S.-Mexican border. Among other outcomes, the PCA checklist can help reduce the costs of pollution prevention and/or monitoring programs by identifying where and when testing of potential point sources should occur, and where and when the testing of water resources should occur. Finally, the GIS tool is extremely useful for the same purpose.

ACKNOWLEDGMENTS

    Special thanks to Heather Duarte, SDSU, for helping with field work and in the GIS lab. This project would not have been possible without the help of Raul Vázquez and Alfredo Angulo from CESPTE, the Tecate Fire Department, and the Municipal DAU.

    This work was sponsored by the Southwest Consortium for Environmental Research and Policy (SCERP) through a cooperative agreement with the U.S. Environmental Protection Agency. SCERP can be contacted for further information through www.scerp.org and scerp@mail.sdsu.edu.

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REFERENCES

    (CADWSAP) California’s Department of Health Services Drinking Water Source Assessment

    and Protection Program.2003. “Possible Contaminating Activities (PCA) Inventory Form for

    Ground Water”. http://www.dhs.ca.gov/ps/ddwem/dwsap/GW/ GW7PCAChecklist5-2002.doc

    accessed Dec 1, 2003.

    Castro Ruiz, J.L. 2002. “Tecate’s Water Supply” in Tecate Baja California: Realties and

    Challenges in a Mexican Border Community. Eds.: Ganster, P., Cuamea Velazques, F., Castro Ruiz, J.L., and Villegas, Angelica. Publ. Institute for Regional Studies of the Californias,

    SDSU Press

    Forster, C. 2005 “Tecate Hydrogeology Assessment” Final Report to IRSC-SDSU. Salt Lake

    City, Utah. Mar 28. pp. 23

    Gersberg, R.M., Brown, C., Zambrano, V., Worthington, K., and Weis, D. 2000.“Quality of

    urban runoff in the Tijuana River Watershed” in The U.S.-Mexican Border Environment: Water Issues Along the U.S.-Mexican Border. Ed.: Paul Westerhoff. SCERP Monograph Series, no. 2, pg. 31.

    Helperin, A. N., Beckman, D. S., Inwood, Dvora. 2001. California’s contaminated groundwater:

    is the State minding the store? Publ. Natural Resources Defense Council, April.

    Holsher, A. 2005. Exploring Water Supply Alternatives for Tecate, Mexico using a System

    Modeling Approach Master’s thesis. University of Utah (March 23). Pp. 112.

    (IRSC) Institute for Regional Studies of the Californias. 2000. International border area

    planning atlas. San Diego: IRSC-SDSU.

    Lozano, M. 1995. Physiochemical Characteristics of the Tecate River. Universidad Autónoma

    de Baja California.

    Luderitz, V., Gerlach, F., Jupner, R., Calleros, J., Pitt, J., Gersberg, R. 2005. Biological

    Assessment of Tecate Creek (U.S.-Mexico) with special regard to self-purification. Bull.

    Southern California Acad. Sci. 104 (1): 1-13.

    (SDSU and COLEF) San Diego State University and Colegio de la Frontera Norte, eds. 2005.

    Tijuana River Watershed Atlas. San Diego: SDSU Press, IRSC.

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