TABLE OF CONTENTS
LIST OF TABLES
LIST OF FIGURES
I. AUTHORITY, JUSTIFICATION AND PARTICIPANTS
A. Authority
B. Justification
C. List of Participating Agencies
D. List of Participating Personnel
II. EXECUTIVE SUMMARY
III. DESCRIPTION OF THE STUDY AREA
A. Aquifer Characteristics
B. Sampling Sites
IV. DESCRIPTION OF THE STUDY
A. Well Construction Methodology
B. Well Completion (Nogales, Sonora and Nogales, Arizona)
C. Cleaning and Decontamination
D. Well Development (Nogales, Sonora and Nogales, Arizona)
E. Pump Installation
F. Well Surveying
G. Sampling Methodology
H. Quality Assurance/Quality Control (QA/QC)
I. Analytical Methods
V. RESULTS
VI. OBSERVATIONS AND COMMENTS
BIBLIOGRAPHY
APPENDIX A - DATA VALIDATION REVIEW
APPENDIX B - NOGALES, SONORA WELL DRILLING INFORMATION
LIST OF ACRONYMS
 

LIST OF TABLES
Table 1 - Well Construction Details for the Monitoring Wells in Nogales, Sonora
Table 2 - Well Construction Details for the Monitoring Wells in Nogales, Arizona
Table 3 - Detection Limits for Volatile Organic Compounds in Soils (Mexican Laboratory)
Table 4 - Detection Limits for Metals in Soil (Mexican Laboratory)
Table 5 - Detection Limits for VOCs in Soils (U.S. Laboratory)
Table 6 - Detection Limits for Trace Metals in Soils (U.S. Laboratory)
Table 7 - U.S. and Mexico Groundwater Sample Containers and Preservation
Table 8 - Field Parameters Collected by the Binational Team
Table 9 - Detection Limits for VOCs in Groundwater (U.S. Laboratory)
Table 10 - Detection Limits for VOCs in Groundwater (Mexican Laboratory)
Table 11 - Detection Limits for Major Cations & Anions in Groundwater (U.S. Laboratory)
Table 12 - Detection Limits for Conventional Parameters and Coliforms in Groundwater (Mexican Laboratory)
Table 13 - Detection Limits for Trace Metals in Groundwater (U.S. Laboratory)
Table 14 - Detection Limits for Metals in Groundwater (Mexican Laboratory)
Table 15 - U.S. Data Summary for VOCs for July 1996
Table 16 - U.S. Data Summary for Inorganic Constituents for July 1996
Table 17 - Mexican Data Summary for Inorganic Constituents for July 1996
Table 18 - U.S. Data Summary for VOCs for April 1997
Table 19 - Mexican Data Summary for VOCs for April 1997
Table 20 - U.S. Data Summary for Inorganic Constituents for April 1997
Table 21 - Mexican Data Summary for Inorganic Constituents for April 1997
Table 22 - Arizona Aquifer Water Quality Standards
Table 23 - Mexican Water Quality Standards
Table A-1 - Mexican Field Blank Data for April 1997
Table A-2 - U.S. Data Calculation of the Project Sampling Precision
Table A-3 - Evaluation of the Analytical Lot of Samples for VOCs for July 1996 and April 1997
Table A-4 - Evaluation of the Analytical Lot of Samples for VOCs for April 1997
Table B-1 - Inventory of Samples Collected w\ the Split Spoon Sampler for detection of metals (M) and volatile organic compounds (VOCs) in Mexico and in the United States
Table B-2 - Soil Penetration Tests
 

LIST OF FIGURES
Figure 1 - Site Location Map
Figure 2 - Well Design - NGW-1 "Parque Industrial"
Figure 3 - Well Design - NGW-2 "Planta PEMEX"
Figure 4 - Well Design - NGW-3 "Ferrocarril"
Figure 5 - Well Design - NGW-4 "Camino Viejo a Cananea"
Figure 6 - Well Design - NGW-5 "Cruz Roja"
Figure 7 - Well Design - NGW-8 "ADEQ#1"
Figure 8 - Well Design - NGW-9 "ADEQ #2"
Figure 9 - Well Design - NGW-10 "Trickey Wash"
Figure 10 - Well Design - NGW-11 "Old Nogales Landfill"
Figure 11 - Well Design - NGW-12 "Wingfield Area"
Figure 12 - Well Design - NGW-13 "Potrero Creek" 

A. Authority

This study and interim report were undertaken by the United States and Mexico pursuant to the International Boundary and Water Commission (IBWC) Joint Report of Principal Engineers Relative to the Joint Monitoring of the Quality of the Groundwaters in the Ambos Nogales Area, dated January 25, 1996.

The joint report approves the formation of a binational team of water quality experts from the United States and Mexico to monitor the quality of the water in the alluvial aquifer along the Nogales Wash in Nogales, Arizona and Nogales, Sonora.

This interim report is issued by the Governments of the United States and Mexico through the two Sections of the International Boundary and Water Commission. This interim report includes information collected during two groundwater monitoring events in Nogales, Arizona and Nogales, Sonora in July 1996 and April 1997. A final report will be published upon the completion of the study.

Copies of this report in English may be obtained from the United States Section of the International Boundary and Water Commission, 4171 N. Mesa, Suite C-310, El Paso, Texas, 79902. Questions regarding the United States information contained in this report may be directed to Ms. Sylvia A. Waggoner at (915) 832-4149 extension 2140 or you may send her e-mail at sylviawaggoner@ibwc.state.gov.

Copies of this report in Spanish may be obtained from the Mexican Section of the International Boundary and Water Commission, Ave. Universidad No. 2180, Zona Chamizal, C.P. 32310 Cd. Juárez, Chihuahua. Questions regarding the information from Mexico contained in this report may be directed to Dr. Alberto Ramirez Lopez at 01152 16 (13-73-11) or (13-99-42) or you may send him e-mail at aramirez@cilamexeua.gob.mx.

B. Justification

The Nogales, Arizona and Nogales, Sonora area (Ambos Nogales) is in an accelerated growth phase, due to the migration and installation of an important number of industries in the region. The accelerated growth along with the topographical conditions in the region and its archaic potable and wastewater conveyance systems, make it difficult to provide adequate sewerage services. The combination of these factors can cause undesirable and uncontrolled infiltration of contaminating substances into the shallow groundwaters in the region. This shallow aquifer is a drinking water aquifer used by private wells in Nogales, Arizona.

After consultations with the responsible agencies in the two countries, the IBWC decided to coordinate the development of a study so as to obtain reliable information on soils and groundwater quality in the shallow aquifer along the Nogales Wash.

The United States Environmental Protection Agency, Region IX (USEPA) provided funding to the United States Section of the IBWC and the Arizona Department of Environmental Quality (ADEQ) to participate in and implement this binational project.

Funding for Mexico's participation in this project was provided by the Comisión Nacional del Agua (CNA) and by the Mexican Section of the IBWC.

C. List of Participating Agencies

United States	Mexico	International
U.S. Environmental Protection Agency	Comisión Nacional del Agua	International Boundary and Water Commission
Arizona Department of Environmental Quality	Gerencia de Aguas Subterráneas
Santa Cruz County Health Department	Gerencia de Saneamiento y Calidad del Agua
City of Nogales, Arizona	Gerencia Regional Noroeste
	Comisión de Agua Potable y Alcantarillado del Estado de Sonora

D. List of Participating Personnel
 

Arizona Department of Environmental Quality Plácido dos Santos, Mario Castañeda, Gloria Koroglanian, Joe Giannelli William Deneke	City of Nogales, Arizona Jose M.Yanez, Michèle A. Kimpel, Richard Caldwell
Santa Cruz County Health Department Ben Stepelton, Michael Alcala	U.S. Environmental Protection Agency, Region IX Evelyn Wachtel, Eugenia McNaughton
Comisión Nacional del Agua, Gerencia de Aguas Subterráneas Rubén Chávez Guillén, Oscar A. Escolero Fuentes, Pedro R. Soto Navarro Juan Manuel, Anzaldo Lara	Comisión Nacional del Agua, Gerencia de Saneamiento y Calidad del Agua Ignacio Castillo Escalante, Valia Maritza Goytia Lea, Graciela Martínez Serratos
Comisión Nacional del Agua, Gerencia Regional Noroeste Martín G. Rodríguez Lara, Lucas Antonio Oroz Rayos, Fernando Guardiola Gámez, Moisés Urrutia Cruz, Francisco Montes de Oca C., Rodrigo Armenta Okada, Ana Cristina García Valenzuela, Rogelio Manríquez Cervantes, Pablo L. Matus Apodaca, Marco A. Cuén Velásquez, Abraham Rivera Lizárraga	Comisión de Agua Potable y Alcantarillado del Estado de Sonora Ruth Eliza Bueras Gómez, Martín Ramos
International Boundary and Water Commission - United States Section Yusuf E. Farran, Sylvia Andrade Waggoner, Steven Tencza, Jorge E. Lerma, Alejandro Bustos	International Boundary and Water Commission - Mexican Section Alberto Ramírez López, Sergio Saúl Solís, Jesús Quintanar, Carlos Mosqueira Claudio Pérez Orona

II. EXECUTIVE SUMMARY

Based on a binational agreement between the United States and Mexico, the IBWC developed the "Joint Report of the Principal Engineers Relative to the Joint Monitoring of the Quality of the Groundwaters to Determine the Presence of Anthropogenic Contaminants in the Transboundary Aquifer in the Nogales, Arizona/Nogales, Sonora Area," dated January 25, 1996, for a joint study of the quality of groundwaters along the alluvial aquifer of the Nogales Wash. Binational meetings to address this concern were initiated in 1993 by both countries. The Nogales Wash originates 8.6 km (5.4 miles) south of the international boundary between the United States and Mexico, and flows north through Nogales, Sonora and Nogales, Arizona. The objective of the study is to obtain reliable data concerning the quality of the groundwaters and the soil along the Nogales Wash. The collection of these data can document whether or not surface activities and discharges into the Nogales Wash have impacted the quality of the groundwater.

Study participants on behalf of the United States were the following: United States Section, IBWC; USEPA, Region IX; ADEQ; Santa Cruz County Health Department; and the City of Nogales, Arizona. The participants in the study on behalf of Mexico were representatives from the Mexican Section, IBWC; CNA; and the State Commission on Potable Water and Sewerage in Sonora (COAPAES). The groundwater sampling teams were comprised, as close as possible, of the same number of water quality professionals from each country. Thirteen sampling wells on either side of the border were established, the majority of them drilled specifically for this study. The exceptions were two pre-existing monitoring wells just north of the international boundary in Nogales, Arizona, one abandoned well at the COAPAES offices, and a potable water well in Nogales, Sonora. The collection of soil samples was conducted during the well drilling phase. Well numbers NGW-1 through 7 are located in Nogales, Sonora and NGW-8 through 13 are located in Nogales, Arizona. The groundwater samples were collected during a total of five sampling events.

This preliminary report presents the results obtained from the first two sampling events. During the first sampling event (July 1996), only the wells in the United States side were sampled, since the monitoring wells in Nogales, Sonora were still under construction. The second sampling event (April 1997) included all the project wells in Ambos Nogales, except for a well that was inaccessible due to paving work in the area and a dry well.

Tetrachloroethylene (PCE) was detected in NGW-9 at a concentration exceeding the Arizona Maximum Contaminant Level (MCL) of 0.005 mg/l. PCE was also detected in wells NGW-5, NGW-6 and NGW-7. The concentrations found at NGW-5 and NGW-7 exceeded the Mexican drinking water standard of 0.008 mg/l. In addition, significant concentrations of arsenic and nitrate were detected in wells NGW-11 and NGW-10, respectively. These concentrations exceeded the Arizona MCLs (0.05 mg/l for arsenic and 10 mg/l for N as nitrate). Total and fecal coliform counts exceeding the Mexican drinking water standards (<1000 MPN/100 ml before chlorination) were detected in NGW-7. The presence of these contaminants was confirmed by the laboratories of both countries.

III. DESCRIPTION OF THE STUDY AREA

The Nogales Wash originates north of Santa Elena, Sonora about 8.6 km (5.4 mi) south of the international boundary between the United States and Mexico. It then flows north through Nogales, Sonora, and Nogales, Arizona. Perennial flow in the Nogales Wash is fed by springs near its head, however, storm flows and uncontrolled sewage discharges also contribute to the flow. Its widest point is located south of the City of Nogales, Sonora where it reaches up to 1.2 km (0.75 mi) in width. The Nogales Wash is encased with concrete close to the international boundary (7 m (23 ft) in width by 5 m (16.4 ft) in height).

A. Aquifer Characteristics

The erosion action caused by the Nogales Wash formed quaternary alluvial deposits (alluvial fans), referred to in the United States literature as the Younger Alluvium (IBWC and ADEQ, 1995). The deposits consist of subangular gravel 2 to 5 cm (0.8-2 in) in diameter, subrounded sand of various grain sizes and yellowish clay. The thickness of the alluvium is over 25 m (82 ft) south of Nogales, Sonora (CNA, 1997) and less than 15 m (49 ft) north of the international boundary (John Carollo Engineers, 1979).

The main aquifer in the area is comprised of quarternary deposits, continental tertiary sedimentary conglomerates and tertiary volcanic sedimentary deposits. The aquifer may be locally confined, however, it is generally unconfined. The main recharge is from infiltration of rainfall through the fractures in the granite, the volcanic rocks and also through the clastic material that forms the aquifer. Since part of the flows in the Nogales Wash that contribute to the recharge of the alluvial aquifer are uncontrolled wastewater discharges, the aquifer is vulnerable to anthropogenic contamination.

The depth to the static water level varies from 5 to 30 m (16.4 to 98.4 ft) close to the international boundary and downtown Nogales, Sonora; from 60 to 140 m (197 to 459 ft) near the industrial area; and from 100 to 140 m (328 to 459 ft) at the southern limit.

The alluvial aquifer formed by the Nogales Wash is not the principal source of water for the City of Nogales, Sonora nor for Nogales, Arizona. However, the alluvial aquifer under the Nogales Wash is tapped by several drinking water wells in Nogales, Arizona. There is a concern regarding the groundwater quality due to low levels (below Arizona maximum contaminant levels) of VOCs found during monitoring activities performed by ADEQ at several monitoring and drinking water wells located along the Nogales Wash in Nogales, Arizona (Earth Technology, 1990 in IBWC and ADEQ, 1995).

B. Sampling Sites

The study tested thirteen wells at twelve different sites within approximately 8 km (5 mi) north and south of the international boundary. Representatives of the participating agencies from the United States and Mexico selected and agreed upon sites for monitoring well placement. All sites were located along the Nogales Wash or its tributaries in areas where the shallow alluvial aquifer is present. Most of the sites lie down gradient of or adjacent to areas where past or present land use includes industrial activity or development that may have had an impact on groundwater quality. In this manner, the location of potential sources of groundwater contamination can be narrowed to a smaller region within the urban area for a more focused study by the appropriate authorities. Such detailed source investigations are beyond the scope of this joint groundwater monitoring program. Specific site descriptions and the rationale for the selection are discussed below. The location of the wells are shown in Figure 1.

Parque Industrial (NGW-1): This site is immediately down gradient from the main industrial area in Nogales, Sonora. This well, located adjacent to the Nogales Wash, will test for effects of any past industrial discharges to the wash or to the groundwater system.

Planta PEMEX (NGW-2): This site will test for petroleum products which may have come from spillage at the PEMEX storage facility. It is located adjacent to the railroad tracks and the Nogales Wash.

Ferrocarril (NGW-3): This site is down gradient from the railroad yard in Nogales, Sonora. The location should determine whether or not groundwater has been affected by spillage from fueling and maintenance operations.

Camino Viejo a Cananea (NGW-4): This site is down gradient from a light industrial area located near the Nogales Wash and to the west along the old road to Cananea.

Cruz Roja (NGW-5): This site is at the confluence of the Nogales Wash and the Cinco de Febrero Wash.

La Tomatera (NGW-6): This existing well (noria) is located in the shallow alluvium near the confluence of the Nogales Wash with one of its major tributaries.

Noria Oficina (NGW-7): This existing shallow well was previously used as a public water supply well. It is located in the same building as the COAPAES offices.

ADEQ #1 and #2 (NGW-8 and NGW-9): These existing wells are monitoring wells drilled by ADEQ in early 1993 to measure groundwater quality at different depths within the alluvial aquifer. NGW-8 is screened near the base of the aquifer while NGW-9 is screened at the water table. This location at the border represents a local point of constriction of the groundwater basin. Most of the flow moving from Mexico into the United States must pass through this narrow zone.

Trickey Wash (NGW-10): This location is adjacent to the former railroad yard in Nogales, Arizona, where fuel spills have caused problems with petroleum contaminated soils. The surrounding land use is primarily retail but has had light industrial use. The Trickey Wash enters the Nogales Wash at this location bringing storm water flows and some wastewater from Mexico.

Old Nogales Landfill (NGW-11): This location is the site of a former sewage treatment plant and a closed municipal landfill site that has not been monitored. Nearby wells have shown trace levels of VOCs. The Nogales Wash is no longer concrete lined at this location.

Wingfield Area (NGW-12): The nearby Wingfield Tire Co. is a gas station and truck wash. Other light industry and produce trucking operations are located south and southeast of this location. Trace levels of VOCs and a parasite, Cryptosporidium, have been detected at a well at the Wingfield station.

Potrero Creek (NGW-13): This site is near the confluence of the Potrero Creek with the Nogales Wash. Potrero Creek is a major tributary and the site of a wetland marsh. West of this site is the United Musical Instruments facility where metal plating sludge and waste solvents were disposed in a lagoon. The lagoon has been cleaned up, however, a trichloroethylene (TCE) plume still exists in the groundwater below this site.

IV. DESCRIPTION OF THE STUDY

The objective of this groundwater sampling project is to collect reliable groundwater quality data from the alluvial aquifer along the Nogales Wash. Data collection will document whether or not surface activities and discharges to the Nogales Wash have significantly affected groundwater quality.

A. Well Construction Methodology

As indicated above, this study includes 13 wells, among which are two existing wells in Mexico (NGW-6 and NGW-7) and two existing wells in the United States (NGW-8 and NGW-9). The remaining nine wells were constructed in accordance with the design proposed in the Well Construction Plan, Nogales Wash Joint United States/Mexico Groundwater Monitoring Program by the International Boundary and Water Commission and Arizona Department of Environmental Quality (IBWC and ADEQ, 1993). This type of design, which is described in the following sections, made it possible to collect representative groundwater samples from the saturated zone within the alluvial aquifer for water quality testing.

The existing wells in Nogales, Sonora, NGW-6 and NGW-7, are hand dug wells completed in the shallow part of the aquifer. NGW-6 (La Tomatera) is a hand-dug well of approximately 2.5 m (8.2 ft) diameter with a total depth of 7.7 m (25.3 ft). NGW-7 (Noria Oficina) is located in the offices of COAPAES. This well is about 2.5 m (8.2 ft) wide on the surface, about 15.24 m (50 ft) deep. It is equipped with a 25 hp, 220V pump.

NGW-8 and NGW-9, the two exiting monitoring wells in Nogales, Arizona, were constructed with a 4-inch schedule 40 PVC casing and completed similarly to the binational wells (IBWC and ADEQ, 1993). NGW-8 is screened close to the bottom of the aquifer with a total depth of 18.07 m (59.3 ft) and NGW-9 is screened at the water table with a total depth of 9.14 m (30 ft).

The drilling of the wells (including the collection of soil samples), well completion and installation of equipment in Nogales, Arizona were conducted by a consulting company under the supervision of the USIBWC and ADEQ. The construction (including the collection of soil samples) and installation of equipment of the five wells in Nogales, Sonora was conducted by CNA (Gerencia de Aguas Subterráneas and Gerencia Regional Noroeste) personnel. Detailed information regarding these activities can be found in their respective well construction reports, Ajay Environmental Consultants, Inc., 1996 and Comisíon Nacional del Agua, 1997.

The total depth of the shallow monitoring wells in Nogales, Arizona, varies between 9.14 m and 18.07 m (30 to 59.3 ft), except for a deeper well, NGW-13, which has a total depth of 46.63 m (153 ft). The total depth of the shallow monitoring wells in Nogales, Sonora, varies between 6.7 m and 14.50 m (22 and 47.6 ft). Tables 1 and 2 show the total depths and screened intervals for the wells sampled in this study. Figures 2 through 12 contain the well design for each well.

Prior to any drilling activities in the United States, Blue Stake, a company that locates underground electrical, natural gas, sewer and telephone lines was employed. This was to ensure that no utilities or pipelines were encountered during the drilling activities. In Mexico, electric (Comisión Federal de Electricidad), telephone, water and sewer authorities were consulted prior to the drilling activities.

1. Nogales, Sonora

a. Monitoring Well Drilling

A total of five monitoring wells were constructed in Nogales, Sonora between November 1996 and January 1997. Four of them (NGW-1, NGW-2, NGW- 4 and NGW-5 on the left (west) bank of the Nogales Wash and one (NGW-3) on the right (east) bank of the Nogales Wash. The well design was similar to the wells drilled in Nogales, Arizona. The well casings were constructed of flush-threaded, four-inch Schedule 40 PVC. The perforation slot size was 0.25 mm (0.01 inches). The wells were screened above the water table to account for water level fluctuations. The screens were extended below the water table to monitor the uppermost part of the aquifer. The filter packing consisted of Colorado Silica Sand No. 10/20. A bentonite annular seal was placed above the screen and a neat cement grout was placed from the surface of the bentonite seal to the top of the casing. Each wellhead was completed with a traffic rated well vault with a tamper-resistant lid installed flush with the ground surface. Each lid was clearly marked with the well identification and date of installation. A water-tight, expandable, locking PVC and neoprene cap was installed at each well to ensure that no cross-contamination could occur. The well number and date of installation were also inscribed on the concrete pad while the concrete was setting. The monitoring wells in Mexico also have designated Grundfos^TM variable speed submersible pumps (e.g., Redi-Flo 2^TM). These pumps will only be installed during groundwater sample collection activities.

During the drilling operations, soil samples were collected for analyses of metals and VOCs. See Tables 3 and 4 for the list of parameters and laboratory detection limits for the Mexican laboratory. One sample from each well was provided to a representative from United States Section, IBWC for analyses of metals and VOCs in the United States. See Tables 5 and 6 for the list of parameters and laboratory detection limits for the United States laboratory.

The drilling method described below was used to drill the wells in Nogales, Sonora. The method, although different from that used by the United States Section, IBWC and ADEQ, always assured the collection of the soil samples for the required purpose. The locations of two of the wells NGW- 4 (Camino Viejo a Cananea) and NGW- 5 (Cruz Roja) were slightly changed, with the agreement of the binational representatives, because the lithological section present made the collection of soil samples extremely difficult in the shallow aquifer. Therefore, the location of NGW-4 was changed to the left (west) margin of the Nogales Wash (the original proposed location was on the right (east) margin). The location of NGW-5 was changed to the left (north) margin of the Cinco de Febrero Wash about 150 m (492 ft) from its confluence with the Nogales Wash. The nature of the lithology found made it necessary to perform an additional geophysical study to determine the thickness of the local sedimentary formation.

All the wells were completed according to the original proposed well construction plan. However, only four of the wells were developed and equipped. The water level was not reached at NGW-2 (PEMEX) in spite of its depth (14.50 m (47.58 ft)). The well was checked during the sampling events, however, water was not encountered. Since no water was encountered, only the field conditions, including photo ionization detector (PID) readings for volatiles, were noted in the field notes.

Several important aspects of the methodology used for drilling the wells are included below. A detailed description regarding the construction of wells and the geophysical study conducted by CNA can be found in CNA, 1997

1. Drilling Equipment

The drilling equipment consisted of a direct rotary drilling rig with wire line system, manufactured by Joy, model 22HD, series 37591. It was mounted on a 1980 International diesel truck, series No. 9.0 DM 2U-4742. They are both owned by CNA.

The method used for drilling was mechanical percussion using the Shelby sampling tube to collect the sample material produced by the drilling operation. The method used always assured the collection of the soil samples for the required purpose for the following reasons:

i. it did not require drilling fluid (e.g., the original composition of the soil remained unchanged),

ii. it prevented collapse of the walls of the well,

iii. it allowed cleaning of the bottom of the well before the collection of soil samples with the split-spoon sampler,

iv. the changes and contrasts of the lithology found were detected immediately, and in many cases the Shelby sampling tube provided soil samples that were nearly undisturbed.

2. Drilling Methodology

This methodology can be summarized in eight steps (CNA, 1997):

i. The Shelby sampling tube was used to initiate the well by advancing the tube with the help of a hammer that was lifted and dropped from a height of 0.5 m (1.64 ft) to open a hole 10.16 cm (4") in diameter.

ii. After reaching a depth of approximately 0.5 m (1.6 ft), the Shelby sampling tube was changed for one that served as a temporary casing (threaded pipe 15.24 cm (6") in diameter, schedule 80 steel pipe, in lengths of 1.50 and 1.0 m (4.92 and 3.28 ft)). This temporary casing was driven by using a cutting piece in its lower end. This cutting piece was used as a guide in the pipe driving process for each well.

iii. The drilling of the next portion of the well was performed with the Shelby sampling tube, after removal of the cutting piece. In this operation, the Shelby sampling tube was pushed to the bottom of the excavated well through the temporary casing in place. The advantage of this temporary casing was that it prevented caving in of the walls, allowing the easy placement of the Shelby sampling tube with a high degree of depth certainty.

iv. These processes were alternated several times up to the point where an additional length of temporary casing pipe was required.

v. Once the additional temporary casing pipe length was in place, the Shelby sampling tube was used to continue the drilling operation.

vi. When it was time to collect a soil sample with the split-spoon sampler, the temporary casing pipe was driven to the required depth, and the Shelby sampling tube was put in place to clean the bottom of the well of any cuttings.

vii. In this manner, with the use of the temporary casing pipe, it was possible to collect the soil samples with the split-spoon sampler with the assurance that no caving in would occur during the collection of the sample.

viii. The drilling operation progressed as described, and once the total or programmed depth was reached, and after the placement of a 10.16 cm (4") diameter PVC pipe casing, the temporary casing pipe was removed. The same pieces of pipe were used as temporary casing for all wells. After each use, they were cleaned and washed with Alconox^TM, a phosphate-free detergent, and rinsed with tap water.

In addition to the drop driver, it was also necessary to use a heavier tool 13.33 cm (5-1/4") in diameter, 4.0 m (13 ft) long, with an approximate weight of 500 kg (1,103 lb). This tool was used to break large intrusive rocks that could not be cut with the Shelby sampling tube.

b. Soil Monitoring

Drilling with the Shelby sampling tube allowed for the collection of representative samples of the lithology through which it passed. The sample was retained inside the Shelby tube, making it simple to recover the sample by drawing out the hammer piece. The sample was placed in a 20-liter (5.3 gal) bucket with a cover. All the material sampled was placed in this type of container (stored in the COAPAES warehouse, in the City of Nogales, Sonora) until the chemical analyses (for metals and VOCs) indicated whether the material could be disposed of without any problems.

The samples of drilled material were collected at each additional 1.5 m (5 ft) of depth, or at every significant change in lithology until the desired depth was reached. For the recovery of the material in the saturated zone, a check valve was placed in the Shelby sampling tube.

From 0.5 to 1.0 kg (1.1 to 2.2 lb) of sample material was collected at each point. Samples were deposited in sealed polyethylene bags for field classification and later shipping to the Soils Laboratory at the Universidad Autónoma de Chapingo (Estado de México). At this laboratory, the samples underwent sieve analyses, and analyses for other parameters as required by the International Unified System for Soil Classification. The bags containing the samples were identified with the well number and designation, depth at which the sample was collected, date and time of sampling. These data will be reported in the final project report.

The standard penetration test was used to collect samples from the vadose zone by means of the split-spoon sampler. This method also provided a measure of the resistance of the soil to the penetration of the sampler. The number (N) of times the hammer is dropped for each 15.24 cm (6") of penetration of the sampler is recorded. These tests were in addition to the tests conducted with the Shelby sampling tube. These tests were conducted every 1.5 m (5ft) or at every significant change in lithology as recommended by IBWC and ADEQ (1993).

The liners with the samples thus collected were placed in polyethylene bags, sealed and placed in an ice chest at a temperature of approximately 4° C with blue ice and later in a refrigerator to be sent to the laboratory for the required analyses.

The criteria for the selection of soil samples to be analyzed for VOCs and metals were those recommended in the Well Construction Plan, that is, one sample per well, whichever was the shallowest, and at the same time with the finest grain, this being the intermediate liner and/or that with the largest amount of sampled material.

The liners with the samples thus selected were divided in the following manner: the intermediate liner was sent to Laboratorios ABC in Mexico City, the lower one was turned over to a representative of United States Section, IBWC following the proper chain of custody procedures. That sample was sent to Bolin Laboratories in Tucson, Arizona. The other liner was sent to the Universidad Autónoma de Chapingo (Estado de México) for studies of lithological characterization (e.g. grain size, moisture content, moisture retention curves, etc.).

Appendix B, Table B-1 shows the list of samples sent to the laboratory for analyses of metals and volatile organic compounds in both Mexico and the United States. Table B-2 contains details on the standard penetration tests conducted during the drilling of the five wells.

For safety purposes, a previously calibrated PID was used to continuously monitor the air quality in the work environment and around the boreholes being drilled.

2. Nogales, Arizona

a. Monitoring Well Drilling

A total of four new wells were drilled in Nogales, Arizona for this study between January and February 1996. Three shallow wells (NGW 10, NGW-11 and NGW-12) were completed using the hollow-stem auger method. The deep well, NGW-13, was completed using the casing advancement method. The well casings were constructed of flush-threaded, four-inch Schedule 40 PVC. The perforation slot size was 0.25 mm (0.01 inches). The wells were screened above the water table to account for water level fluctuations. The screens were extended below the water table to monitor the uppermost part of the aquifer. The filter packing consisted of Colorado Silica Sand No. 10/20. A bentonite annular seal was placed above the screen and a neat cement grout was placed from the surface of the bentonite seal to the top of the casing. Each wellhead was completed with a traffic rated well vault with a tamper-resistant lid installed flush with the ground surface. Each lid was clearly marked with the well identification and date of installation. A water-tight, expandable, locking PVC and neoprene cap was installed at each well to ensure that no cross-contamination could occur. The well number and date of installation were also inscribed on the concrete pad while the concrete was setting. All monitoring wells were equipped with a dedicated Grundfos^TM variable speed submersible pump (e.g., Redi-Flo 2^TM). This type of submersible pump can achieve a high flow rate of approximately 0.3 liters per second (LPs) (5 gallons per minute (gpm)) for purging activities and a low flow rate of 100 milliliters per minute (ml/min) for sampling. Additional well construction details are presented in the project Well Construction Plan (IBWC and ADEQ, 1993) and in the Monitoring Well Completion Report dated April 1996, therefore, construction details for these wells are not included in this report. The well completion details are presented in Figures 7 through 12 and are summarized in Table 2.

b. Soil Monitoring

The monitoring well boreholes were drilled using a hollow-stem auger drill rig. All sampling equipment was cleaned before the sampling of each borehole interval for each well. Split-spoon samples were collected in each borehole at 1.5 m (5 ft) intervals and at observed major lithologic changes encountered during drilling to the total depth of the monitoring well borehole. One split-spoon soil sample was also collected from the uppermost observed fine-grained sediment layer in a vadose zone. Samples from the uppermost fine-grained layer in the vadose zone were submitted to the laboratory for analysis for VOCs (aromatic and halogenated organic compounds) and trace metals. See Tables 5 and 6 for the list of parameters and laboratory detection limits for the United States laboratory. One sample from each well was provided to a representative from the Mexican delegation for determination of the same parameters in Mexico. See Tables 3 and 4 for the list of parameters and laboratory detection limits for the Mexican laboratory. The remainder of samples were used to document the site geology.

During drilling, measurements were taken of the driller's breathing zone and in the borehole using a NHu photo ionization detector (or similar instrument) and a triple meter (explosivity, oxygen, and hydrogen sulfide). Drilling activities were performed with Level D Personal Protective Equipment (PPE) according to the project Health and Safety plan. More detailed information regarding the drilling and soil monitoring activities is presented in the monitoring well completion report for these wells (Ajay Environmental Consultants, 1996).

B. Well Completion (Nogales, Sonora and Nogales, Arizona)

The monitoring wells in Nogales, Sonora and Nogales, Arizona were designed according to specifications by the project well construction plan (IBWC and ADEQ, 1993). The field notes and construction details for the wells constructed in Nogales, Arizona are presented in the well construction report prepared by Ajay Environmental Consultants, Inc. (1996). The field notes and construction details for the wells drilled in Nogales, Sonora can be found in CNA (1997).

All of the monitoring wells were completed with Schedule 40 PVC, 10.16 cm (4") diameter pipe in lengths of 1.5 and 3 m (5 and 10 ft). The screen had a slot size of 0.25 mm (0.01 inches) to prevent the passage of fine sediments into the well. The length of the screen was at most 3 m (10 ft) above the static water level and for the total remaining depth of the well. This allows flow from levels fluctuating due to drops during drought periods and recovery during the rainy season. The screen was placed at least 1.2 m (4 ft) below the static water level to monitor the uppermost part of the aquifer. A threaded cover was placed on the first length of slotted pipe, then the pipe was lowered through the temporary casing or through the hollow stem auger. The smooth pipe was placed from 1.5 m (5 ft) above the static water level to ground elevation.

With the casing pipe suspended from the top to prevent buckling, and centered in the well, a silica sand filter of Colorado No. 10/20 sand was placed, free of debris, to fill the annular space existing between the casing pipe and the walls of the drilled well, from the bottom of the well up to a point 0.6 - 1 m (2 -3 ft) above the upper end of the screen. A separating ring to act as an impermeable seal 1.0 m (3.3 ft) in length, consisting of powdered bentonite, was placed over the sand filter and finally the space from the top of the bentonite ring to the ground level was filled with a cement grout. This was done to prevent infiltration from the surface into the well.

As protection for the wellhead, a special traffic-rated vault 30.48 cm (12") in diameter and 30.48 cm (12") long was placed at ground elevation and encased in concrete. The traffic cover was placed and bolted on the steel pipe piece with two 1.90 cm (3/4") diameter bolts. The well number and date of installation were inscribed on the concrete pad while the concrete was setting.

The wellhead cover was placed between 0.0 and 0.3 m (0 and 1 ft) above natural ground level to prevent surface runoff from entering the well. In cases where there was a concrete floor or pavement, the wellhead cover was placed at floor or pavement level. This was not the case where there was no pavement of any kind.

The wellhead covers placed at the end of the 10.16 cm (4") diameter PVC casing pipe are equipped with a waterproof closure. The cover is designed to provide connections for the power for the pump, the discharge hose and also allows for the measurement of the water level. This cover is permanently installed in the wells in Nogales, Arizona. In Nogales, Sonora; the cover and pumps are installed only during sample collection activities. The wells in Nogales, Sonora are equipped with a rubber gasket, which was adjusted under pressure for a protective waterproof closure.

Figures 2 through 6 contain the completion diagrams for NGW-1 through NGW-5 in Nogales, Sonora. Figures 7 through 12 contain well completion details for wells NGW-8 through NGW-13.

C. Cleaning and Decontamination

1. Nogales, Sonora

All the cleaning and decontamination of the sampling equipment in Mexico were performed at the COAPAES Laboratory in Nogales, Sonora. This activity was critical and necessary in order to collect representative soil samples and to prevent cross contamination. Its importance was due to the magnitude of the detection limits required in the chemical analyses, which were in the order of parts per billion (ppb) for volatile organic compounds, and parts per million (ppm) for trace metals.

a. Liners

Liners are brass cylinders 5.08 cm (2") in inside diameter by 15.24 cm (6") in length, with thin walls in the order of 0.15 cm (0.06 in) thick, which are placed inside the split-spoon sampler during the collection of soil samples. The process for their cleaning and decontamination consisted of the following steps:

I. washing with Alconox^TM detergent and tap water, followed by rinsing with deionized water,

ii. rinsing with 10% nitric acid solution and again rinsing with deionized water,

iii. rinsing with pesticide grade hexane,

iv. drying at ambient temperature,

v. final rinsing with deionized water and drying at ambient temperature.

The rinsing operations with 10% nitric acid solution as well as those with hexane and deionized water were performed in transparent, polyethylene, corrosion-resistant buckets. Handling of the liners was with stainless steel pliers.

During the washing operation, prolonged contact with hexane vapors was avoided by performing the operation in a well ventilated area of the COAPAES laboratory.

b. Plastic Caps for Liners

These are polyethylene caps which are placed on each end of the liner after the collection of the sample and the placement of Teflon^TM paper. Since these were not in direct contact with the soil sample, it was sufficient to wash them with Alconox^TM detergent and a scrubbing mesh. They were rinsed first with tap water and then with deionized water and allowed to dry on a drying rack.

c. Split-Spoon Sampler

The split-spoon sampler is a steel tube with a cutting piece coupled to its lower end. At its upper end, it was connected to a type AW drilling pipe by means of a head coupling. Its length is 45.72 cm (18"), sufficient to fit three 15.24 cm (6") liners in it. The inside diameter is 5.2 cm (2.1"). The steel tube was cut longitudinally to allow the easy removal of the liners which are placed in it prior to the sampling operation. Its head had a valve which allowed for the purging of sediments, and prevented the sample from falling out of the tube. For the sampling of unconsolidated materials, a basket was used inside the cutting piece of the sampler.

The cleaning and decontamination of the split-spoon sampler were performed after each sampling event. Since it was not possible to rent a steam washer, cleaning was performed at the COAPAES Laboratory in Nogales, Sonora.

All the soil that adhered to the sampler was removed in a dry process by brushing with a nylon bristle brush. After brushing, it was washed with Alconox^TM detergent and tap water and then rinsed with deionized water. The soil removed was placed in a basket to be later disposed of with other cuttings from the drilling process. The 10% nitric acid solution was not used on this equipment because it would corrode the steel. The same washing process was performed on the split-spoon sampler baskets.

Once all the equipment was washed for collection of the soil samples, a certain number of completely dry and clean liners and plastic caps were stored in a transparent polyethylene container with a cover. The number to be stored was determined by estimating the number of sampling events that would be performed during a day's drilling.

2. Nogales, Arizona

All the cleaning and decontamination of the drilling and sampling equipment in Nogales, Arizona was performed in accordance with the Well Construction Plan (IBWC and ADEQ, 1993). Cleaning consisted of washing in an Alconox^TM (non-phosphate detergent) solution, rinsing with tap water, rinsing with distilled/deionized water, rinsing with 10% nitric acid, rinsing with distilled/deionized water, rinsing with pesticide grade hexane, air drying the sampling equipment, and then rinsing with distilled/deionized water. In addition, the hollow-stem augers were steam cleaned prior to the drilling of the borehole.

D. Well Development (Nogales, Sonora and Nogales, Arizona)

The purpose of well development was to restore natural hydraulic conditions after drilling in order to enhance yield and remove finer materials to enable water that is representative of the aquifer to move into the zone to be monitored. The development of the monitoring wells was performed after the grout had cured adequately so that it would not be drawn into the wellbore. Development was accomplished using pumping, bailing, and mechanical surging. Development was initiated by removal of excess sediment in the well and was started at the slowest possible pumping rate. The pumping rate was gradually increased as development proceeded. Development of the wells was performed as guided by the following criteria and continued until these criteria were met:

1. Well water had a turbidity of less than 5 Nephelometric Turbidity Units (NTU) or best attainable, as determined by field personnel;

2. Sediment remaining in the bottom of the well bore did not exceed 5 percent of the total screened casing length;

3. Physical parameters such as pH, conductivity, and temperature were stabilized within 10% over two successive casing and filter pack (30 percent porosity assumed) volumes of water.

The wells in Nogales, Sonora were developed using a surge block to mix the sediment inside the well then removing the water/sediment mixture manually with a bailer. For this purpose, the surge block 8.9 cm (3.5") in diameter was attached to three segments (3 m (10 ft) in length) of 2.5 cm (1") PVC pipe. The water was removed with a single valve, PVC bailer, 8.9 cm (3.5") in diameter and .91 m (3 ft) in length (CNA, 1997).

All well development water was contained. The water was later disposed of through the city sewer system after securing sewer authority approval.

E. Pump Installation

After completion of well development, the groundwater monitoring wells were equipped with dedicated Grundfos^TM variable speed submersible sampling pumps. This type of submersible pump can achieve a high flow rate of approximately 0.3 liters per second (LPs) (5 gallons per minute (gpm)) for purging activities and a low flow rate of 100 milliliters per minute (ml/min) for sampling. The flow rate was controlled with a portable 115 or 220 V power converter (BMI/MPI Converter).

Each well has a designated pump. These pumps were installed approximately .3 to .5 m (1 to 1.5 ft) above the bottom of the monitoring well and were equipped with a 1.27 cm (0.5") riser pipe or tube to the wellhead in order to perform groundwater sampling.

As indicated above, the wellhead covers are equipped with a waterproof closure. This cover was permanently installed in the wells in Nogales, Arizona. In Nogales, Arizona the well covers also support the weight of the pump, the discharge hose and the electrical cord. The installation of the pumping equipment was performed by the drilling consultant (Ajay Environmental Consultants, Inc., 1996) under the supervision of the IBWC and ADEQ.

In Nogales, Sonora, for security reasons, the pumps are installed only during sampling events. Each pump and associated tubing is clearly marked indicating the well number to which it corresponds in order to avoid cross contamination. The pumping equipment (pumps, tubing, covers and converter, etc) is stored at the Mexican Section's offices in Nogales, Sonora. The installation of the equipment was performed by CNA (Gerencia de Aguas Subterraneas y de la Regional Noroeste) (CNA, 1997).

F. Well Surveying

In Nogales, Arizona, following completion of the monitoring wells, a registered surveyor was contracted to perform a wellhead elevation survey having an accuracy of plus or minus .003 m (0.01 ft) (Ajay Environmental Consultants, Inc., 1996). The survey is used to calculate the actual elevation of the groundwater and evaluate the direction of groundwater flow. The survey of the wellhead elevations of the wells in Nogales, Sonora is pending.

G. Sampling Methodology

The groundwater sampling program in the Nogales, Arizona/Nogales, Sonora area was initiated on July 15, 1996. Only the Nogales, Arizona wells were sampled during the first sampling event except for NGW-13 which could not be sampled because of a faulty submersible pump. The second sampling event included all the wells in Nogales, Sonora and Nogales, Arizona except for two. Due to paving work in the vicinity of NGW-3 the well was inaccessible and although the well had been completed, the wellhead had to be removed and replaced after the paving work was completed. Also, NGW-2 was not sampled. As mentioned before, NGW-2 is a dry well. All wells were sampled in accordance with the Quality Assurance Project Plan, Arizona Department of Environmental Quality (ADEQ QAPP), the Manual of Groundwater Monitoring Sampling Procedures EPA RCRA Groundwater Monitoring Technical Enforcement Guidance Document (TEGD) (OSWER. 9950) and the project work plan (International Boundary and Water Commission and Arizona Department of Environmental Quality, 1995). This report presents the results obtained from only the first two sampling events.

For the monitoring wells outfitted with the Grundfos^TM variable speed submersible pumps (e.g., Redi-Flo 2^TM), groundwater sampling was performed as follows:

1. All pieces of field equipment (i.e., Hydrolab, turbidity meter and PID) were calibrated according to manufacturer instructions.

2. Prior to purging and sampling of the wells, the working area and the area around the wellhead were checked for volatiles with a PID. No problems were encountered.

3. All personnel who worked on well sampling wore disposable latex gloves to prevent contamination of the sampled material and as personal protection.

4. Depth to water was measured from the top of the well casing to the top of the water surface to the nearest 0.003 m (0.01 ft) prior to sampling. An electrical sounder was used to measure the depth to water. The sounder was washed with an Alconox^TM (non-phosphate detergent) solution and rinsed first with tap water and then with deionized or distilled water after each use. Only the wet portion was cleaned unless the rest of the line appeared dirty. The elevation of groundwater in meters and feet was calculated, when possible, and recorded using the elevation of the ground surface at the wellhead and depth to water.

5. A minimum of three casing volumes of water were purged from each well prior to sampling using the dedicated submersible pumps. The purge water was collected into a measured bucket to determine the pump flow rate. The required well volume was determined by the following formula:

(7.48)()(D2)(L)	where:	V = volume of water in the well (gallons (gal))
V = ------------------------------		D = inside diameter of the well (in)
(144)(4)		L = height of standing water in the well (ft)
V = (0.25)()(D2)(L)(1000)	where:	V = volume of water in the well (liters)
		D = inside diameter of the well (meters)
		L = height of standing water in the well (meters)

Purge water from wells in Mexico was collected in 200-liter (55-gallon) drums, which were stored at COAPAES in Nogales, Sonora, until the samples were analyzed. Once the results were evaluated, the purge water was disposed of through the city sewer system. All purge water from the Nogales, Arizona monitoring wells was also contained in 200-liter (55-gallon) drums and disposed of through the city sewer system after the approval of the appropriate sewer authority was secured. Each drum was labeled with the well(s) number(s) that the water came from. Table 8 presents a list of the field parameters measured by the binational team in these wells during the first and second quarterly sampling events.

6. Specific conductance, pH, turbidity and temperature were recorded at a minimum of 19 liters (5 gal) intervals. Samples were collected when at least three casing volumes of water were removed and the above parameters stabilized (10 percent or less difference between successive readings). If a well was pumped or bailed dry during removal of casing water (and recovery was slow), three casing volumes were not removed. The well was allowed to recover to within 80% of its original casing volume prior to sample collection.

7. Prior to sample collection, a clean plastic sheet was laid down around the wellhead. Clean latex gloves were used by samplers at each sample point. Groundwater samples were collected immediately after purging was complete. Samples were collected with their respective dedicated submersible pumps.

8. Samples were collected in the following order: VOCs, Total Petroleum Hydrocarbons (TPH), major cations and ions, trace metals, and total and fecal coliform.

9. Samples for VOCs were sampled at the lowest possible non-disruptive purging rate so that the sample container was headspace-free. The maximum sampling flow rate observed for VOCs was 250 ml/min. All such samples were collected in 40-milliliter (ml) vials with Teflon^TM septums prepared by the laboratory with preservative added. A test vial was filled with groundwater and the pH checked with pH paper to determine if the quantity of the preservative added to the laboratory-supplied vials was enough to lower the sample pH to below 2. If the pH of the test vial was above 2, then more hydrochloric acid (HCl) was added to the sample collection vials and the pH test was repeated. The test vial was discarded. The lowest possible flow rates were used while filling the sample containers to avoid agitation. The containers were immediately capped so that volatilization was minimized. A headspace-free sample was achieved by filling the container to slightly overflowing, forming a meniscus at the mouth of the container. The cap was placed upon the convex meniscus and tightly sealed. To check that the sample was air-free, the container was inverted and the cap gently tapped. The absence of entrapped air indicated a successful seal. When air was evident in the container, the entire sample was discarded and another sample was collected.

10. The flow rate was increased slightly to 300 ml/min for the collection of the remaining samples. TPH samples were collected in an amber bottle. Sufficient HCl was added to lower the pH of the sample to <2. The pH was tested by placing a small amount of sample into the bottle cap. The pH was then tested with pH paper. HCl was added to the sample when needed. The water in the cap was discarded.

11. Samples to be analyzed for major cations and anions and for trace metals were collected in three plastic one-liter bottles with screwed on caps. Mexico used inert nalgene plastic 1-liter bottles with screwed on caps. The first one-liter bottle was used for collecting samples for analysis of major cations and anions. Second one-liter bottle was used for collecting samples for analysis of nitrate. The samples for the Mexican laboratory were preserved with sulfuric acid (H₂SO₄) to a pH of <2. The sample for the United States laboratory were not preserved. The other one-liter bottle, for trace metals analysis, was preserved with nitric acid (HNO₃ ). The water for the trace metals sample was filtered using a disposable polypropylene 0.45 micron filter. A 1,000 ml-volume of filtered sample was discarded prior to sample collection. Sample turbidity was recorded prior to filtering the sample. The container was filled to the top and capped. The sample pH was tested for a pH value below 2 by pouring a small amount of filtered sample into the bottle cap and checking the pH with pH paper. The liquid in the cap was discarded after checking the pH.

12. Samples for total and fecal coliform were collected in two plastic 100-ml containers (not with whirl bags as indicated in the work plan). These containers were supplied by the laboratory and arrived sterilized with a plastic heat-shrunk wrap sealing the lid. The seal was not broken until right before the sample was collected.

13. Carbonate and bicarbonate alkalinity were determined in the laboratory. Dissolved oxygen was not determined in the groundwater samples at this time.

14. Samples of groundwater collected in the field were labeled immediately. Labels with adhesive backing were completed with indelible ink and affixed to the side of the sample container. Plastic bottles were labeled directly on the container. Information written on the label for the laboratory included:

a. Site Location
b. Monitoring well number
c. Analyses required
d. Initials of sampler
e. Date
f. Time
g. Preservative added

The label was attached securely to the sample container to minimize loss or mutilation. Each label was filled out as completely as possible prior to taking the sample. VOCs vials and 100 ml plastic containers for coliform samples were double-bagged in plastic bags with tops that self-seal.

Sample containers were supplied by the analytical laboratory selected to analyze the samples. Table 7 contains information regarding the sample containers, additional details about preservation methods, and laboratory holding times for the various parameters.

15. Well purging and sampling data for each well were recorded in the field log book at the time of sampling.

For the two existing water supply wells in Nogales, Sonora (COAPAES NGW-7 and La Tomatera NGW-6), the steps outlined above were followed with the following modifications or exceptions:

a. Depth to water was measured after the well had remained unused for 24 hours.

b. The field parameters, such as temperature, pH, and specific conductance (EC) were recorded for the water extracted from the wells. Water level measurements as well as physical characteristics of the water, including color, odor, and turbidity, were also recorded. The samples were collected once these parameters stabilized.

c. Samples were collected using disposable bailers constructed of inert plastic suspended with nylon rope. The bailers were used once and discarded after sample collection. Since the bailers were prepackaged and free of contamination, no cleaning or equipment blanks were necessary. The bailers were handled by personnel using latex gloves. Measures were taken to prevent the nylon rope from being contaminated.

H. Quality Assurance/Quality Control (QA/QC)

1. QA/QC in the Field

a. Chain of Custody

The chain-of-custody for possession and responsibility of samples was documented from the time and place of sample acquisition to the time and place of their final destination. Strict chain-of-custody procedures outlined in the work plan were followed and documented in the field log books.

b. Transportation of Samples

Samples were stored in portable ice chests and cooled to 4^o C with ice immediately after sample collection until transported to the laboratory. Custody seals were placed on each bottle cap. The VOCs vials and the total and fecal coliform bottles placed in a plastic bag and sealed. The custody seals were placed on the plastic bags. Glass containers were wrapped with bubble wrap. Additional ice was added to the ice chest prior to shipping as needed. The ice chests were stored in a shady location during sample collection.

The chain of custody form and other sample paperwork was enclosed in the ice chest by placing it in a plastic bag and taping the bag to the inside of the ice chest lid.

The ice chests were sealed with strapping tape. Two custody seals were placed on the front of the cooler so that the custody seals extended from the lid to the main body of the ice chest. Clear tape was placed over each custody seal on the outside of the ice chest. The drain plug was checked to ensure that it was closed prior to shipping.

Total and fecal coliform samples required transport to the laboratory within six hours for immediate sample extraction and incubation. Field personnel or a courier service hand delivered the samples to the laboratory as soon as practicable after sample collection.

c. Preservation

All samples were placed in ice immediately after sample collection to lower the temperature to 4^o C until they were delivered to the laboratory for analysis. When required, samples were preserved by adding hydrochloric acid, sulfuric acid or nitric acid, as requested by the laboratory, to reduce the pH of the samples to less than 2.

d. Duplicate Samples

One duplicate sample was collected during the first sampling event at NGW-11. Two duplicate samples were collected during the second sampling event. One duplicate was collected at NGW-11 and the other at NGW-6 for analysis of VOCs, TPH, conventional parameters, metals, nitrate and bacteriological parameters.

e. Field Blanks

Three field blanks were collected during the second sampling event. The field blanks were collected at NGW-8 and 9, NGW-12 and NGW-4 for analysis of VOCs, TPH, conventional parameters, metals, nitrate and bacteriological parameters.

f. Trip Blanks

During the first and second sampling events, trip blanks were included in every shipping container. These samples were analyzed for VOCs.

2. QA/QC in the Laboratory

Laboratory QA/QC was accomplished by using such items as surrogate spikes, matrix spikes, duplicates, reagent blanks and calibration checks.

I. Analytical Methods

1. Soil Samples

Soil samples were collected in duplicate for delivery to the appropriate laboratories in both countries. The samples were analyzed in each country using available laboratory methodology with their respective detection limits. The samples collected from the wells in Nogales, Sonora were sent for analysis to Laboratorios ABC in Mexico City, D.F., which had been contracted for this purpose. The parameters analyzed were: VOCs, by EPA Method 8240 and metals by EPA Method 6010. Tables 3 and 4 contain the list of parameters and method detection limits. Soil samples were collected during the drilling activities of the Nogales, Arizona wells according to the Soil Collection Procedures described in the Well Construction Plan developed for this project. In Nogales, Arizona, samples from the uppermost observed fine-grained sediment layer were submitted to Copper State Analytical Lab, Inc. for analysis for VOCs (aromatic and halogenated organic compounds) using EPA Methods 8010 and 8020, and trace metals using EPA Methods presented in Table 6. Table 5 contains the list of parameters and detection limits for EPA Methods 8010 and 8020. The soil results will be included in the final report.

2. Groundwater Samples

Groundwater samples were collected in duplicate for delivery to the appropriate laboratories in both countries. Samples were analyzed in each country using available laboratory methodology with their respective detection limits. The following groups of parameters were analyzed in groundwater samples collected during the first two sampling rounds of this study:

a. Volatile Organic Compounds (VOCs) by EPA Standard Method 502.2 in the United States (See Table 9 for specific compounds), and by EPA Method 8240 in Mexico (See Table 10 for specific compounds);

b. Total Petroleum Hydrocarbons by modified EPA Standard Method 8015 (Diesel), or an equivalent method in the United States and in Mexico;

c. Major cations and anions by EPA Standard Methods in the United States (see Table 11 for specific compounds), and by the methods shown in Table 12 in Mexico;

d. Trace metals by EPA Standard Methods in the United States (see Table 13 for specific compounds), and by the MA-AA-01 method in Mexico (See Table 14);

e. Total coliform and fecal coliform bacteria by EPA Standard Methods 909A and 909C in the United States, and by the MA-MB-01 and MA-MB-03 methods in Mexico; and

f. Field parameters temperature (T), pH, electrical conductivity (EC), and turbidity. Mexico utilized the protocol established by CNA for the measurement of these parameters. Carbonate and bicarbonate alkalinity, and dissolved oxygen were not measured at this time.

VOCs and trace metals were tested because of historical industrial activity along the Nogales Wash and the known VOCs occurrence in groundwater of the area. Major cations and anions were tested to characterize general hydrogeochemical conditions and to provide data for hydrogeologic interpretations. Coliform bacteria were tested because the Nogales Wash has shown elevated levels of bacteria for a long period of time. Field parameters were measured as a matter of standard practice, to test whether adequate purging of the well was accomplished, and to serve as a quality control check.

V. RESULTS

All groundwater samples collected by the United States were analyzed by Bolin Laboratories, Inc., of Tucson and Phoenix, Arizona according to the analytical methods and parameters described above. Bolin Laboratory is an Arizona certified laboratory. Groundwater samples collected by Mexico were analyzed by Laboratorio Central de la Gerencia de Saneamiento y Calidad del Agua, CNA, México, D.F. (heavy metals), Laboratorio de Saneamiento y Calidad del Agua de la Gerencia Regional Noroeste, CNA, Hermosillo, Sonora (conventional parameters) and Laboratorio ABC in México, D.F. (volatile organic compounds). Laboratorio ABC is approved by CNA based on the law of metrology and standardization (Ley de Metrología y Normalización) and is accredited by the Department of Standards (Dirección General de Normas (DGN)) through the national system of accreditation for testing laboratories (Sistema Nacional de Acreditamiento de Laboratorios de Prueba (SINALP)).

Tables 15, 16, 18 and 20 present a summary of the detected constituents for the groundwater samples collected by the United States. Tetrachloroethylene (PCE) was detected in monitoring well NGW-11 (0.0013 mg/l) during the July 1996 sampling event. NGW-11 also showed elevated levels of arsenic (0.048 mg/l).

PCE was detected in monitoring wells NGW-5 (0.140 mg/l), NGW-6 (0.0035 mg/l), NGW-7 (0.046 mg/l), and NGW-9 (0.0087 mg/l) during the April 1997 sampling event. Low levels of additional VOCs were detected in monitoring wells NGW-4, NGW-5, NGW-6 and NGW-7. Vinyl chloride was detected in NGW-4 (0.0021 mg/l).

In April 1997, nitrate (as nitrogen) was detected in monitoring wells NGW 5 (6.30 mg/l), NGW-6 (6.6 mg/l) NGW- 9 (6.2 mg/l) and NGW-10 (13.9 mg/l). Iron (4.11 mg/l) and manganese (5.48 mg/l) were detected in monitoring well NGW-4. Arsenic was detected in monitoring well NGW-11 (0.057 mg/l). High counts of total and fecal coliform were found in NGW-7 by both countries during the April 1997 sampling activity.

Tables 17, 19 and 21 present the results obtained by the Mexican laboratories. The results for the samples collected in April 1997 show the following concentrations of tetrachloroethylene (PCE): NGW- 5 (57.66 ug/l), NGW -6 (2.41 ug/l), NGW-7 (17.46 ug/l) and NGW-9 (3.37 ug/l).

Total xylenes were also detected in NGW-7 (7.05 ug/l). The highest levels of arsenic were found in NGW-10 (0.0284 mg/l) and NGW-11 (0.032 mg/l). The highest nitrate levels were found in NGW-8 (19.8 mg/l) and NGW-10 (13.5 mg/l).

Appendix A presents the data validation performed on these data. Precision and accuracy for the United States data were within the project established data quality objectives. Cation and anion balances were performed for all the groundwater samples collected by the United States The ion balance difference was less than 10 % for all the groundwater samples, except for well NGW-8 (15.3%). This difference will be investigated.

Appendix A also presents procedures and calculations concerning quality control and quality assurance for the analytical methods used in Mexico. These show that, for the results of April 1997, there was compliance with the data quality objectives established for this project.

Travel blanks were used to check for contamination during shipping and handling during both sampling events. The travel blanks were prepared by the contract laboratory and analyzed for the same VOCs parameters as the groundwater samples. Trihalomethanes (THMs) were detected during the July 1996 trip blanks. Also, chloroform was detected in one of the trip blanks prepared by the United States laboratory at a very low concentration (0.0028 mg/l) during the second sampling event. A letter sent to ADEQ from the Arizona certified laboratory (Bolin Labs of Phoenix, AZ) dated June 13, 1997 states that Bolin Labs used treated bottled water to prepare their travel blanks. Bolin Labs has addressed this situation by purchasing a Brita filtration unit that is now used to filter all bottled water before it is used to prepare travel blanks.

Three field blanks were collected during the second sampling activity (NGW-16, NGW-17, and NGW-18). NGW-16 was prepared using DI water supplied by the Arizona State Laboratory. NGW-17 and NGW-18 were prepared using DI water supplied by the Mexican lab. The United States laboratory detected chloroform in NGW-16 at 0.0007 mg/l. Chloroform, dibromomethane, bromodichloromethane, and bromoform were detected in NGW-17 and NGW-18. Except for chloroform (detected at 0.0009 mg/l in NGW-5), none of the THMs were detected in the groundwater samples. In addition, the Mexican laboratory detected low concentrations of lead and copper in the Mexican lab-supplied DI water. These constituents were not detected in any of the groundwater samples.

The analyses by the Mexican laboratory during the first event did not include field blanks or travel blanks. In the second round, bromodichloromethane and dibromochloromethane were detected in the field blank NGW-17. These two constituents and bromoform were detected in field blank NGW-18. These constituents were not detected in any of the groundwater samples, which suggests contamination at the origin. The blanks for heavy metals and conventional parameters did not yield significant results.

VI. OBSERVATIONS AND COMMENTS

This interim report presents the groundwater monitoring data gathered in the first two sampling quarterly events for the project monitoring wells installed in Nogales, Arizona and Nogales, Sonora. An integrated final binational report will be developed after the end of the project monitoring activities.

In general, the project data quality objectives for precision and accuracy were met during these sampling events by both laboratories. In some cases, major differences were found in the reported concentration values of arsenic, barium and nitrates by both countries. The source of these differences will be investigated by the binational group.

Cation and anion balance differences were less than 10% for all groundwater samples, collected by the United States, with the exception of well NGW-8 (15.3%). The source of this difference will be investigated by the binational group.

Tetrachloroethylene (PCE) was detected in NGW-9 at a concentration exceeding the Arizona MCL of 0.005 mg/l. Vinyl chloride was detected in NGW-4 (0.0021 mg/l). This value exceeded the Arizona MCL for Vinyl Chloride (0.002 mg/l). In addition, PCE was also detected in wells NGW-5, NGW-6 and NGW-7. The PCE concentrations found at NGW-5 and NGW-7 exceeded the Mexican drinking water standard of 0.008 mg/l. PCE detections at these wells were confirmed by the laboratories of both countries. However, Mexican PCE reported concentrations at these wells were half of those reported by the United States laboratory. Again, the source of these differences will be investigated by the binational group.

Nitrate (as nitrogen) was detected in monitoring well NGW-10 (13.9 mg/l by the United States and 13.5 mg/l by Mexico) at levels exceeding the Arizona Aquifer Water Quality Standard of 10 mg/l and the Mexican drinking water quality standard of 5 mg/l during April 1997. Nitrate was also detected at levels exceeding the Mexican drinking water quality standard in monitoring wells NGW-5 and 6 (6.30 mg/l and 6.6 mg/l) reported by the U.S. laboratory.

Arsenic was detected in monitoring well NGW-11 at levels exceeding both the Arizona Aquifer Water Quality Standards (0.05 mg/l ) and the Mexican drinking water quality standards (0.05 mg/l).

Iron and manganese were found in monitoring well NGW-4 (4.11 mg/l and 5.48 mg/l, respectively, reported by the U.S.) exceeding the Mexican drinking water quality standards (0.3 mg/l and 0.1 mg/l, respectively).

A high count of total and fecal coliform was detected in NGW-7 by both countries during the April 1997 sampling activity. This exceeded the Mexican drinking water standard (1,000 NMP/100 ml prior to chlorination).

Tables 22 and 23 include the United States and Mexican water quality standards, respectively.

The purpose of this interim report is to make available the project soil and groundwater quality data to the local communities. There are several ongoing projects dealing with improving the wastewater infrastructure and wellhead protection activities in the Ambos Nogales area. These projects can benefit with the project-generated water quality information.

* Includes end cap of 0.10 m (0.3 ft)
The sum of the casing length does not include the 0.30 m (0.1 ft) end cap

PQL = PRACTICAL QUANTITATION LIMIT
MDL = DETECTION LIMITS

* = EPA 7470

* Faulty Turbidity Meter
NS - not sampled

PQL = Practical Quantitation Limits
MDL = Detection Limits

* Manual de Métodos de Análisis. 1995. Comisión Nacional del Agua. Subdirección General Técnica. Gerencia de Saneamiento y Calidad del Agua

*Manual de Métodos de Análisis. 1995. Comisión Nacional del Agua Subdirección General Técnica. Gerencia de Saneamiento y Calidad del Agua

Z = Detection could not be confirmed by GC/MS. Data for informational purposes only
Note: All concentration values in mg/l

Note: All concentration values in mg/l. Coliform in CFU/100 ml;
N/A - Not Analyzed NC - Not Calculated
RPD - Relative Percent Difference
a - Exceeded Arizona Aquifer Water Quality Standards
b - Exceeded Mexican Drinking Water Standards

All concentration values are expressed in mg/l
* NMP/100mL
N.D. = Not Detectable
N.A. = Not Analyzed
a - Exceeds Arizona Aquifer Water Quality Standards
b - Exceeds Mexican Drinking Water Standards

Note: All concentration values in mg/l.
N/A - Not Analyzed
a - Exceeded Arizona Aquifer Water Quality Standards
b - Exceeded Mexican Drinking Water Standards

Note: All concentration values in mg/l.
FB=Field Blank
a - Exceeded Arizona Aquifer Water Quality Standards
b - Exceeded Mexican Drinking Water Standards

** Total Petroleum Hydrocarbons (mg/L)
All concentration values in ug/L
N.D.= not detectable
NC = not calculated
Samples NGW-15 and NGW-14, are duplicate samples of NGW-6 and NGW-11, respectively
a - Exceeds Arizona Aquifer Water Quality Standards
b - Exceeds Mexican Drinking Water Standards
RPD = Relative Percent Difference

Note: All concentration values in mg/l. Coliform in CFU/100 ml
NC = Not Calculated
TNTC = Too numerous to count
FB = Field Blank
a -Exceeded Arizona Aquifer Water Quality Standards
b -Exceeded Mexican Drinking Water Standards
RPD = Relative Percent Difference

* NMP/100mL
NGW-15 is the duplicate of NGW-6
All concentration values in mg/l
NC = Not Calculated
a - Exceeds Arizona Aquifer Water Quality Standards
b - Exceeds Mexican Drinking Water Standards

* NMP/100mL
NGW-14 is the duplicate of NGW-11
All concentration values in mg/l
NC = Not Calculated
RPD - Relative Percent Difference
a - Exceeds Arizona Aquifer Water Quality Standards
b - Exceeds Mexican Drinking Water Standards

International Boundary and Water Commission and Arizona Department of Environmental Quality, 1995. Work Plan for the Nogales Wash Joint U.S./Mexico Groundwater Monitoring Program, September 7, 1995.

Comisión Nacional del Agua. Programa Binacional de Monitoreo de Aguas Subterráneas sobre el Arroyo Los Nogales: Informe Sobre la Perforación de Pozos de Monitoreo y Muestreo de Suelos en Nogales, Sonora. Diciembre de 1997.

John Carollo Engineers, 1979. Nogales Wastewater Project Report - 1979, prepared for the U.S. Section, International Boundary and Water Commission, April 1979.

International Boundary and Water Commission and Arizona Department of Environmental Quality, 1993. Well Construction Plan, Nogales Wash Joint U.S./Mexico Groundwater Monitoring Program, May 3, 1993.

Ajay Environmental Consultants, Inc., 1996. Monitoring Well Completion Report, Groundwater Monitoring Program, Nogales, Santa Cruz County, Arizona, prepared for the International Boundary and Water Commission, United States and Mexico, U.S. Section, IBWC Contract No. IBM 95-34, April 1996.

U.S. Environmental Protection Agency, RCRA Groundwater Monitoring Technical Enforcement Guidance Document (TEGD) (OSWER-9950.0)

Comisión Nacional del Agua. Subdirección General Técnica. Gerencia de Saneamiento y Calidad del Agua. Manual de Métodos de Análisis, 1995.

The following deviation from the proposed field sampling protocols occurred during the sampling:

a) Samples for VOCs compounds were sampled at the lowest possible non disruptive purging rate. Maximum sampling flow rate for VOCs observed was 250 ml/min.

b) Samples for total and fecal coliform were collected in two plastic 100-ml containers and not with whirl bags. These containers arrived sterilized from the respective laboratory. The containers from the United States laboratory were sealed with a plastic heat shrunk rap around the lid. The seal was not broken until right before the sample was collected. The containers prepared in Mexico were autoclaved for sterilization and were sealed with a special autoclave adhesive tape.

c) Samples to be analyzed for major cations and anions and for trace metals were collected in three plastic one-liter bottles. The first one-liter bottle was used for collecting samples for analysis of major cations and anions. This sample was not acidified or filtered. The second one-liter bottle was used for collecting samples for analysis for nitrate. The samples for the Mexican laboratory were preserved with sulfuric acid (H₂SO₄) to a pH of <2. The sample for the United States laboratory was not preserved since the laboratory would be analyzing the samples within the 48-hour holding time. The other one-liter bottle, for trace metals analysis, was preserved with nitric acid (HNO₃ ) and was filtered. Duplicate samples sent to the Arizona State Laboratory were collected according to the project sampling plan.

d) Performance standard samples were not used at this time.

e) The labs used for this project did not require doubling the sampling volume for their laboratory QA/QC sample.

f) Field carbonate and bicarbonate alkalinity and dissolved oxygen parameters were not determined in the groundwater samples at this time. All samples were collected within the established well purging criteria.

SAMPLES HOLDING TIME REQUIREMENTS

Chain of Custody records and laboratory reports were checked for appropriate sample holding times requirements. All samples were analyzed within the required holding times during both sampling events.

TRAVEL BLANKS

Travel blanks were used to check for contamination during shipping and handling during both sampling events. The travel blanks were prepared by the laboratory and analyzed for the same VOCs parameters as the groundwater samples. Trihalomethanes (THMs) were detected in the United States travel blanks during the July 1996 trip blanks. Also, Chloroform was detected in one of the trip blanks at a very low concentration (2.8 parts per billion (ppb)) during the second sampling event. A letter sent to ADEQ from the Arizona certified laboratory (Bolin Labs of Phoenix, AZ) dated June 13, 1997 states that Bolin Labs used treated bottled water to prepare their travel blanks. Bolin Labs addressed this situation by purchasing a Brita filtration unit that is now used to filter all bottled water before it is used to prepare travel blanks.

Mexico included travel blanks only for the second sampling event. Analytical results did not present any constituent in significant amounts.

FIELD BLANKS

Three field blanks were collected during the second sampling activity (NGW-16, NGW-17, and NGW-18). NGW-16 was prepared using DI water supplied by the Arizona State Laboratory. NGW-17 and NGW-18 were prepared using DI water supplied by the Mexican lab. Chloroform was detected in NGW-16 at 0.7 ppb. Chloroform, bromodichloromethane, chlorodibromomethane, and bromoform were detected in NGW-17 and NGW-18. Except for chloroform (detected at 0.9 ppb in NGW-5), none of the THMs were detected in the groundwater samples. In addition, the Mexican laboratory detected low concentrations of lead and copper in the DI water supplied by the Mexican Lab. These constituents were not detected in any of the groundwater samples. Analytical results obtained by the United States laboratory are presented in Table 19 and 20 and the results obtained by the Mexican laboratory are presented in Table A-1.

PRECISION

Precision was determined through duplicate analyses. Precision was calculated as a relative percent difference (RPD) as follows:

	(a-b)
Precision =	________________	x 100
	((a+b)/2)

	where:
	a = larger value of two duplicate analyses
	b = smaller value of two duplicate analyses

Precision for field duplicate sample analysis was targeted to be 30% or lower for VOCs and 35% or lower for metals for groundwater samples. These limits apply to any measurement that is at least ten times greater than the background level of the detector or the method detection limit.

A duplicate sample was collected at NGW-11 and sent to the Arizona State laboratory during the first sampling event and to Bolin Labs of Phoenix, AZ (an Arizona certified laboratory) during the second sampling event. These duplicate samples were used to determine the project sampling precision.

All detected metals that had a concentration ten times or higher than the respective method detection limit met the project precision criteria for both sampling events. The TCE concentrations detected at the original sample (1.3 parts per billion (ppb)) and the duplicate sample (1.8 ppb) during the first sampling event gave a percent difference value slighter higher (32.2%) than the project precision criteria for VOCs. Table A-2 presents the RPD values obtained by the United States for the duplicate samples collected during both sampling activities. Similarly, the precision values found for the Mexican data were within the 30% limit. RPD values for the data from Mexican laboratories are included in Table 17.

ACCURACY

Accuracy was determined by the analyses of surrogate and matrix spiked samples. Accuracy was calculated as percent recovery as follows:

	(a-b)
Accuracy =	________________	x 100
	c

	where:
	a = measured concentration in spiked sample
	b = measured concentration in unspiked sample
	c = actual concentration of spike added

Recovery is generally expected to be within 70-130%

Accuracy was determined by the analysis of surrogate and matrix spiked samples and calculated as percent recovery. Targeted percent recovery for VOCs was within 70-130 %. The contract laboratory analytical reports submitted to ADEQ were reviewed for surrogate recovery data. All surrogate recoveries reported by these labs were within these criteria. The evaluation of the analytical lot is shown in Table A-3

For the data from the Mexican laboratories, for volatile organic compounds, the accuracy was determined through the analysis of additional samples with known concentration surrogate standards. It is calculated as a percentage of recovery. The recommended range is 70 - 130 %. The evaluation of the analytical lot is shown in Table A-4. The accuracy for the data from the Mexican laboratories was calculated as follows:

	b
%Recovery =	________________	x 100
	a

	where:
	a = theoretical concentration in spiked sample
	b = measured concentration in spiked sample

ION BALANCES

A cation/anion balance was calculated for all groundwater samples collected by the United States during the second sampling event. Targeted ion balance was set to be 10% or less discrepant. Except for NGW-8 which had a 15.3% difference, all samples presented a balance with no more than 10% difference.

N.D.= NOT DETECTABLE

Note: All concentration values in mg/l
NA - Not Analyzed
NC - Not Calculated
PQL - Practical Quantitation Limit
RPD - Relative Percent Difference

Well: NGW - 1: "PARQUE INDUSTRIAL"

Depth: 1.50 , 20 November 1996, 10:00 hours

TEST	LINER	TIMES  HAMMER  DROPPED	PENETRATION  cm	RECOVERY  %	OBSERVATIONS
TEST 1	LINER No 3	35	15	95	CLAYEY/SANDY MATERIAL
TEST 2	LINER No 2	17	15	90	SANDY/CLAYEY MATERIAL
TEST 3	LINER No 1	18	15	100	SANDY/CLAYEY MATERIAL AND GRAVEL

Depth: 3.00 M, 20 November 1996, 13:45 hours

TEST	LINER	TIMES  HAMMER  DROPPED	PENETRATION  cm	RECOVERY  %	OBSERVATIONS
TEST 1	LINER No 3	78	15	80	GRAVEL MATERIAL AND ROCK  FRAGMENTS
TEST 2	LINER No 2	100	15	75	NO RECOVERY
TEST 3	LINER No 1	82	15	87	NO RECOVERY

Well: NGW - 2: "PEMEX"

27 November 1996, 10:50 hours

TEST	LINER	TIMES  HAMMER  DROPPED	PENETRATION  cm	RECOVERY  %	OBSERVATIONS
TEST 1	LINER No 3	44	15	100	CLAYEY/SANDY MATERIAL
TEST 2	LINER No 2	61	15	93	SANDY/CLAYEY MATERIAL
TEST 3	LINER No 1	37	15	97	SANDY/CLAYEY MATERIAL

Depth: 3.00 M, 27 November 1996, 13:05 hours

TEST	LINER	TIMES  HAMMER  DROPPED	PENETRATION  cm	RECOVERY  %	OBSERVATIONS
TEST 2	LINER No 2	1	15	100	SANDY/CLAYEY MATERIAL AND PEA  GRAVEL
TEST 3	LINER No 1	47	5	31	SANDY MATERIAL, PEA GRAVEL AND  GRAVEL

Depth: 4.50 M,27 November 1996, 15:45 h

TEST	LINER	TIMES  HAMMER  DROPPED	PENETRATION  cm	RECOVERY  %	OBSERVATIONS
TEST 1	LINER No 1	33	15	100	SANDY/CLAYEY MATERIAL AND PEA  GRAVEL
TEST 2	LINER No 2	42	15	100	SANDY/CLAYEY MATERIAL AND PEA  GRAVEL
TEST 3	LINER No 3	100	11	0	ROCK FRAGMENTS OBSTRUCTED THE  LINER OPENING

note: the test at 6.0 m was not done due to the presence of gravel

Well: NGW - 3: "FERROCARRILES"

Depth: 1.50 M, 9 January 1997, 13:05 hours

TEST	LINER	TIMES  HAMMER  DROPPED	PENETRATION  cm	RECOVERY  %	OBSERVATIONS
TEST 1	LINER No 3	10	15	100	CLAYEY/SANDY MATERIAL
TEST 2	LINER No 2	10	15	50	SANDY/CLAYEY MATERIAL
TEST 3	LINER No 1	18	15	13	SANDY/CLAYEY MATERIAL

Depth: 3.00 M, 9 January 1997, 15:30 hours

TEST	LINER	TIMES  HAMMER  DROPPED	PENETRATION  cm	RECOVERY  %	OBSERVATIONS
TEST 1	LINER No 3	31	15	98	SANDY/CLAYEY MATERIAL, SOME PEA  GRAVEL
TEST 2	LINER No 2	29	15	90	SANDY/CLAYEY MATERIAL, SOME PEA  GRAVEL
TEST 3	LINER No 1	30	15	39	SANDY MATERIAL, SOME PEA GRAVEL

Depth: 4.50 M, 9 January 1997, 16:26 hours

TEST	LINER	TIMES  HAMMER  DROPPED	PENETRATION  cm	RECOVERY  %	OBSERVATIONS
TEST 1	LINER No 3	93	15	75	SANDY/CLAYEY MATERIAL AND PEA  GRAVEL
TEST 2	LINER No 2	80	15	98	SANDY/CLAYEY MATERIAL AND PEA  GRAVEL
TEST 3	LINER No 1	74	15	16	ROCK FRAGMENTS OBSTRUCTED THE  LINER OPENING

Well: NGW - 4: "CAMINO VIEJO A CANANEA"

Depth: 1.50 M, 22 October 1996, 11:40 hours

TEST	LINER	TIMES  HAMMER  DROPPED	PENETRATION  cm	RECOVERY  %	OBSERVATIONS
TEST 1	LINER No 3	35	15	95	CLAYEY/SANDY MATERIAL
TEST	LINER	TIMES  HAMMER  DROPPED	PENETRATION  cm	RECOVERY  %	OBSERVATIONS
TEST 2	LINER No 2	17	15	100	SANDY/CLAYEY MATERIAL
TEST 3	LINER No 1	18	15	100	SANDY/CLAYEY MATERIAL

Depth: 3.0 M, 22 October 1996, hours

TEST	LINER	TIMES  HAMMER  DROPPED	PENETRATION  cm	RECOVERY  %	OBSERVATIONS
TEST 1	LINER No 3	67	15	0	NO SAMPLE RECOVERED
TEST 2	LINER No 2	91	15	0	DUE TO
TEST 3	LINER No 1	74	15	0	HIGH MOISTURE CONTENT

Depth: 4.50 M, 22 October 1996, hours

TEST	LINER	TIMES  HAMMER  DROPPED	PENETRATION  cm	RECOVERY  %	OBSERVATIONS
TEST 1	LINER No 3	51	15	0	NO SAMPLE RECOVERED
TEST 2	LINER No 2	68	15	0	DUE TO
TEST 3	LINER No 1	74	15	0	HIGH MOISTURE CONTENT

Well: NGW -- 5: "CRUZ ROJA"

Depth: 1.60 M, 21 January 1997, 13:15 hours

TEST	LINER	TIMES  HAMMER  DROPPED	PENETRATION  cm	RECOVERY  %	OBSERVATIONS
TEST 1	LINER No 3	21	15	97	LARGE GRAIN SAND WITH PEA GRAVEL
TEST 2	LINER No 2	28	15	98	LARGE GRAIN SAND WITH PEA GRAVEL
TEST 3	LINER No 1	17	15	39	LARGE GRAIN SAND WITH PEA GRAVEL

Depth: 3.0 M, 21 January 1997, 15:00 hours

TEST	LINER	TIMES  HAMMER  DROPPED	PENETRATION  cm	RECOVERY  %	OBSERVATIONS
TEST 1	LINER No 3	23	15	100	LARGE GRAIN SAND, VERY HUMID
TEST 2	LINER No 2	21	15	100	LARGE GRAIN SAND, VERY HUMID
TEST 3	LINER No 1	31	15	91	LARGE GRAIN SAND, VERY HUMID

Depth: 4.50 M, 22 January 1997, 12:45 hours

TEST	LINER	TIMES  HAMMER  DROPPED	PENETRATION  cm	RECOVERY  %	OBSERVATIONS
TEST 1	LINER No 3	22	15	99	LARGE GRAIN SAND WITH PEA GRAVEL,  VERY HUMID
TEST 2	LINER No 2	28	15	62	LARGE GRAIN SAND WITH PEA GRAVEL,  VERY HUMID
TEST 3	LINER No 1	37	15	0	PEA GRAVEL IN RECOVERY TUBE

Depth: 6.00 M, 22 January 1997, 15:40 hours

TEST	LINER	TIMES  HAMMER  DROPPED	PENETRATION  cm	RECOVERY  %	OBSERVATIONS
TEST 1	LINER No 3	49	15	97	LARGE GRAIN SAND, VERY HUMID
TEST 2	LINER No 2	26	15	99	LARGE GRAIN SAND, VERY HUMID
TEST 3	LINER No 1	10	15	100	LARGE GRAIN SAND, VERY HUMID

Depth: 7.50 M, 23 January 1997, 8:45 hours

TEST	LINER	TIMES  HAMMER  DROPPED	PENETRATION  cm	RECOVERY  %	OBSERVATIONS
TEST 1	LINER No 3	34	15	100	CLAY AND SATURATED SAND
TEST 2	LINER No 2	42	15	100	CLAY AND SATURATED SAND
TEST 3	LINER No 1	35	15	49	CLAY AND SATURATED SAND