Chevron •RECEi

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{T^Anne Wagner, PhD CManager, Environmental and

Public Policy

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Chevron IVIinIng Inc. Questa Mine P.O. Box 469 Questa, NM 87556 Tel 575-586-7625 Fax 575-586-0811 awagne@chevron,com

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June 15, 2010

William C. Olson, Chief Ground Water Quality Bureau New Mexico Environment Department P.O. Box 5469 Santa Fe, NM 87502-5469

RE: Additional Monitoring for DP-933

Dear Mr. Olson:

Chevron Mining Inc. (CMI) received your letter of May 17, 2010 concerning its November 30, 2009 response to NMED's request for sampling Guadalupe Mountain monitoring wells GM-4 and GM-5. The letter dismissed CMI's concerns about the need for the sampling and required CMI to submit a sampling plan for the wells with an implementation schedule. As indicated in our letter of November 30, 2009, based on ground water flow, this sampling is not warranted since there is no likelihood that water from CMI's Tailing Facility has impacted groundwater in the vicinity o f the wells. However, even though CMI does not believe the sampling is warranted, it is submitting the attached plan with an implementation schedule prepared by Arcadis.

As noted in the plan, CMi proposes that the sampling take place approximately two (2) weeks following NMED's approval o f the plan. Also please note that the plan includes well re­development and the water from the well development will be discharged on the ground some distance from the wellhead.

Please let me know if you have any questions or need further information.

Sincerely,

y, r I . /

Anne Wagner, PhD

Enclosures

cc:J. Fox, NMED M. Purcell, EPA S. DesGeorges, BLM

9158743

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ARCADIS Infrastructure, environment, buildings

Memorandum To:

Anne Wagner (CMI)

From:

Tim Cox (ARCADIS)

Date:

June 14, 2010

Copies:

Armando Martinez (CMI) Mike Coats (CEMC) Erin Koch (CEMC)

ARCADIS Project No.:

CO001337.0003

Prepared for

Chevron Mining Inc.

Prepared by;

ARCADIS U.S., Inc.

630 Plaza Drive

Highlands Ranch

Colorado 80129

Tel 720.344.3500

Fax 720.344.3535

Subject:

Plan for Sampling Guadalupe Mountain Wells

At the request of Chevron Mining Inc. (CMI), ARCADIS has prepared a plan for sampling Guadalupe Mountain monitoring wells GM-4 and GM-5, as required by New Mexico Environment Department (NMED). CMI received an October 29, 2009 letter from NMED requiring a change in monitoring and reporting requirements for Discharge Permit 933 (DP-933). The letter stated that a large quantity of seepage is unaccounted for and escaping to the basal bedrock (volcanic) aquifer along the western side of the tailing facility and that the current monitoring networi< of wells is inadequate to detect possible seepage flow to the west. NMED requested that two existing wells within the Guadalupe Mountains (GM-4 and GM-5) be sampled (Figure 1). CMI responded to NMED in a November 30, 2009 letter disagreeing that the current monitoring program is inadequate and that sampling of the two wells is not warranted because available historical and recent groundwater flow and chemical data from the Remedial Investigation shows that groundwater is not impacted west ofthe tailing facility where the two wells are located. In spite ofthe compelling data and evidence provided by CMI, NMED issued a May 17, 2010 letter to CMI stating that NMED determined that the information provided by CMI did not present a reasonable justification for not sampling the two wells, and required submittal of a plan with an implementation schedule for sampling the two wells and an updated potentiometric surface map for the volcanic aquifer.

Plan for Sampling

The following presents a plan for sampling (Plan) Guadalupe Mountain wells GM-4 and GM-5, which includes an initial inspection of the wells, re-development, sampling and analysis, documentation ofthe sampling and analytical results, and schedule to perform the sampling.

Background

Guadalupe Mountain monitoring wells GM-4 and GM-5 are located northwest and west, respectively, of the CMI tailing facility in Questa, New Mexico (Figure 1). The wells are on land owned by the Bureau of Land Management and were installed during a characterization study to quantify the hydraulic properties of the

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volcanic aquifer underlying and downgradient of the then proposed Guadalupe Mountain tailing facility (Dames & Moore, 1988). Both wells are reported to be constructed with steel casing and screened in the volcanic aquifer that underlies the Guadalupe Mountains. GM-4 is screened from 848 to 888 feet below ground surface (bgs) and GM-5 is screened from 525 to 625 feet bgs. Each well was last sampled in January 1988. Additional infonnation for the wells is contained in Table 1.

Table 1 - Available Information for Guadalupe Mountain Wells

Well ID

GM-4

GM-5

Date Drilled

11/30/1987

1/7/1988

Top of Casing Elev (ft)

7,940 est.

7,644 est.

Borehol e Depth (ft, bgs)

1,207

632

Well > Depth (ft,

bgs)

890

630

^Well Material

,8.1 ID steel casing

8.1" ID steel casing

Screened Interval (ft,

>.bgs) i

848 to 888

525 to 625

Depth to Water

(ft, bgs)

-790

-504

Static Water Level (ft)

7,149.8 (1/1988)

7,140.5 (1/1988)

Well Inspection

NMED stated in their May 17, 2010 letter that they, along with BLM, inspected the wells and found them to be in good condition; however, there is no description of that inspection and what it involved. The two wells were also viewed by NMED and CMI personnel in November 2009. The GM-4 wellhead consisted of the steel well casing and cap. GM-5 appeared to have a pump already installed in the well with a generator to power the pump. The GM-5 wellhead was within a fenced area.

Because ofthe unknown condition ofthe wells, each well will be inspected by CMI prior to sampling. The purpose of the inspection is to check the integrity of the wells and to determine if there are potential obstructions that could potentially damage sampling equipment or prevent sampling. The well inspections will include checking the well head and surface seal to determine if surface contamination may have occurred. A weighted tape will be lowered into each well to check for casing continuity and any potential obstructions that could prevent sampling of the well. A water level probe will then be used to measure the depth to water. NMED will be notified if a well cannot be sampled along with the necessary documentation. The Bureau of Land Management will be contacted to obtain access to each well location prior to the inspections. *

The location of each well will be surveyed to determine its northing and easting based on the State planer coordinate system. The elevation of the ground surface and top of casing (measuring point) will also be surveyed.

Well Re-Development

Each well will be re-developed after it has been inspected. Re-development is necessary to remove any potential stagnant water or chemically-altered water that may be present since the wells were last sampled in 1988. Each well is reported to be constructed with steel casing and over time corrosion of the steel or possible bacterial scaling may have occurred that could affect the water quality. The objectives of the

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development are to remove stagnant water and to ensure free-flowing groundwater enters the well from the surrounding aquifer prior to sample collection. Field parameters including pH, specific conductance, temperature, dissolved oxygen, and redox potential will be measured during development and development will cease when the field parameters values stabilize, and at least one casing volume of water has been removed. Development water will be placed on the ground away from the well head. The pumping devise used for re-development will be selected after the initial well inspections. A high-capacity bladder pump may be used, or a submersible pump may be necessary if a greater volume of water needs to be removed from the well.

Sample Collection

Each well will be sampled approximately one day after re-development to allow the water level in the well to recover to static conditions. Groundwater sampling procedures will be the same as those currently used for DP-933, which involves low-flow purging (<500 milliliters per minute) until field parameters stabilize. The depth to water will be measured during purging to ensure minimal drawdown in the well and that formation water is entering the well casing. Water samples will be collected by decreasing the pumping rate to <200 milliliters per minute and slowly transferring the water to sample containers provided by the laboratory. Quality control (QC) samples (matrix spike/matrix spike duplicate and field duplicate) will be collected at the same frequency QC samples are collected for DP-933,

Chemical Analyses

Water samples will be shipped to Hall Environmental Analysis Laboratory in Albuquerque, New Mexico for testing, which is the same laboratory that is used for analytical testing for DP-933, Samples will be analyzed for the Group 1, 2, and 3 parameters specified in DP-933:

• Group 1: Field parameters: water level, temperature, pH, specific conductivity,

• Group 2: General chemistry parameters: calcium, magnesium, sodium, potassium, carbonate, bicarbonate, sulfate, chloride, nitrate, fluoride, and total dissolved solids,

• Group 3: Dissolved metals: aluminum, arsenic, barium, beryllium, cadmium, chromium, cobalt, copper, iron, lead, manganese, mercury (total concentration only), molybdenum, nickel, selenium, silver, uranium, vanadium, and zinc.

All data will be validated and qualified using guidance from the U,S, EPA Contract Laboratory Program National Functional Guidelines for Inorganic Data Review (EPA, 1994), CMI maintains an environmental data management system developed specifically for the site that consists of a relational database constructed using Microsoft Access, Data from the laboratory will be provided to CMI or other person(s) and will be uploaded to the database following validation.

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ARCADIS

Documentation

Field measurements and observations during sample collection will be recorded in a field logbook and on field data sheets for each sample location,

A report will be prepared that documents sampling ofthe two Guadalupe Mountain wells and results. The report will summarize the sampling procedures and data validation. Field parameters and analytical results for the water samples will be summarized in tabular format. Water levels from the two wells will be used with recent water levels from other monitoring wells at the tailing facility to construct a potentiometric surface map for the volcanic aquifer underlying the Dam No, 4 impoundment and Guadalupe Mountains,

Schedule

The inspection and sampling of the wells will take place approximately two weeks after CMI receives NMED approval of this Plan, The report documenting the sampling will be prepared and submitted to NMED approximately six weeks after the sampling is conducted. Future sampling of the wells will be determined after the analytical results and updated groundwater flow direction within the volcanic aquifer have been evaluated.

References

CMI, 2009, Response to October 29, 2009 Change of Monitoring and Reporting for DP-933, Letter from CMI to NMED dated November 30,

Dames & Moore, 1988, Hydrogeology and Underflow Estimates in the Vicinity ofthe Proposed Guadalupe Mountain Tailings Facility; prepared for Molycorp, Inc, March 17,

EPA, 1994, EPA Contract Laboratory Program National Functional Guidelines for Inorganic Review,

NMED, 2009, Change of Monitoring and Reporting Requirements for DP-933, Chevron Mining Inc, Letter from NMED to CMI dated October 29,

NMED, 2010, Additional Monitoring for DP-933, Chevron Mining Inc, Letter from NMED to CMI dated May 17,

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020398

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