Skip Links

USGS - science for a changing world

Data Series 933

Prepared in cooperation with the Mining and Minerals Division of the State of New Mexico Energy, Minerals and Natural Resources Department

Hydrologic Data From Wells at or in the Vicinity of the San Juan Coal Mine, San Juan County, New Mexico, 1973–2013

By Anne M. Stewart and Nicole Thomas

Acknowledgments

The authors thank Mrs. Nadine Mead and the Mead Family Trust and Mr. R.G. Hunt for allowing us to access and measure water levels at wells on their private property and for their hospitality and aid in inclement weather. We thank Mining and Minerals Division personnel and New Mexico Environment Department personnel for hosting us at their offices while we collected archived data. We thank Public Service Company of New Mexico–San Juan Generating Station personnel and San Juan Coal Mine and BHP Billiton personnel for providing permission to access and monitor groundwater at wells on their properties, for their speedy responses to our requests for information, for field support, and especially for the hospitality and shelter extended to our field personnel in snowstorms, rainstorms, windstorms, and electrical storms.

Abstract

In 2010, in cooperation with the Mining and Minerals Division (MMD) of the State of New Mexico Energy, Minerals and Natural Resources Department, the U.S. Geological Survey (USGS) initiated a 4-year assessment of hydrologic conditions at the San Juan coal mine (SJCM), located about 14 miles west-northwest of the city of Farmington, San Juan County, New Mexico. The mine produces coal for power generation at the adjacent San Juan Generating Station (SJGS) and stores coal-combustion byproducts from the SJGS in mined-out surface-mining pits. The purpose of the hydrologic assessment is to identify groundwater flow paths away from SJCM coal-combustion-byproduct storage sites that might allow metals that may be leached from coal-combustion byproducts to eventually reach wells or streams after regional dewatering ceases and groundwater recovers to predevelopment levels. The hydrologic assessment, undertaken between 2010 and 2013, included compilation of existing data. The purpose of this report is to present data that were acquired and compiled by the USGS for the SJCM hydrologic assessment.

Introduction

In 2010, in cooperation with the Mining and Minerals Division (MMD) of the State of New Mexico Energy, Minerals and Natural Resources Department, the U.S. Geological Survey (USGS) initiated a 4-year assessment of hydrologic conditions at the San Juan coal mine (SJCM), located about 14 miles west-northwest of the city of Farmington, San Juan County, New Mexico (fig. 1). The mine produces coal for power generation at the adjacent San Juan Generating Station (SJGS) and stores coal-combustion byproducts from the SJGS in mined-out surface-mining pits. The purpose of the hydrologic assessment is to identify groundwater flow paths away from SJCM coal-combustion-byproduct storage sites that might allow metals that may be leached from coal-combustion byproducts to eventually reach wells or streams after regional dewatering ceases and groundwater recovers to predevelopment levels. The hydrologic assessment, undertaken between 2010 and 2013, included review of existing literature; depth-to-groundwater measurements taken at local and regional wells; compilation of existing data; and numerical groundwater-flow modeling. The compiled data used or considered in the hydrologic assessment are presented in this report.

Purpose and Scope

The purpose of this report is to present data that were acquired and compiled by the USGS for the SJCM hydrologic assessment. Acquired data were collected between 1973 and 2013 by the USGS, SJCM and SJGS operators, and SJCM and SJGS contractors and consultants. The wells from which data were collected are located in the north-central part of San Juan County, New Mexico; however, the hydrologic assessment extends slightly into La Plata County, Colorado (fig. 1). Collected data include the locations of monitored wells and identification (by SJCM and SJGS consultants or by USGS personnel) of the water-bearing unit(s) into which each well is completed (table 1); depth-to-groundwater measurements taken from monitoring wells at or in the vicinity of the SJCM (table 2) located in the central San Juan Basin (fig. 1); and a subset of chemical analyses from groundwater samples drawn from monitoring wells (table 3).

Figure 1. Map showing study area location, San Juan coal mine boundaries, monitoring well locations, and water-bearing units of completion for monitoring wells, San Juan County, New Mexico. (Prints 11 x 17 inces)

Table 1. Locations and water-bearing units of completion of monitoring wells at or in the vicinity of the San Juan coal mine and period of record of depth-to-groundwater data collected from the monitoring wells, San Juan County, New Mexico.

Table 2. Depth-to-groundwater measurements taken from monitoring wells at or in the vicinity of the San Juan coal mine during the period of record, San Juan County, New Mexico.

Table 3. Concentrations of arsenic, calcium, chloride, sodium, sulfate, sulfide, and total dissolved solids in groundwater-quality samples collected from monitoring wells at or in the vicinity of the San Juan coal mine during the period of record, San Juan County, New Mexico.

Hydrologic Data

Depths to groundwater were measured for this project between 2011 and 2013 by the USGS. Additional depth-to-groundwater data, for USGS-monitored wells with periods of record preceding this project, were obtained from the USGS National Water Information System (NWIS) database (http://waterdata.usgs.gov/nwis), from the MMD digital database (http://www.emnrd.state.nm.us/MMD/gismapminedata.html), or from review of reports and permitting documents submitted to the MMD by the SJCM (archived at the MMD). In tables 2 and 3, these data sources are indicated as “SJCM Reporting via MMD,” with the exception of one data point found in the SJCM mining permit (Permit 2009–01, 700-, 800-, and 900-series attachments, July 6, 2010), which was cited explicitly. Data were not included in this report for SJCM wells that were abandoned and destroyed prior to the 2010 initiation of the USGS hydrological assessment project.

The USGS also located and reviewed SJGS groundwater data submitted by the SJGS operator, Public Service Company of New Mexico (PNM), in various quarterly, annual, supplemental, and consultant reports to the New Mexico Environment Department (NMED) or to its predecessor agency, the New Mexico Environmental Improvement Division (NMEID; records of this former agency are archived at NMED and are available to the public). These data sources are indicated in tables 2 and 3 as “PNM Reporting via NMED” and “Other via NMED,” respectively (in the latter case, the entry is footnoted with the name of the report in which the data were found).

SJGS-reported groundwater elevations at each well were subtracted from associated measuring-point altitudes documented in PNM or SJGS reports to calculate the depth-to-groundwater data from measuring-point altitudes included in table 2 (cited as “PNM Reporting”). The purpose of this correction was to allow time series of calculated water-level elevations to be normalized to USGS-surveyed measuring-point altitudes.

Wells listed in table 1 and shown in figure 1 were included in the hydrologic assessment. Depths-to-groundwater measurements taken by USGS personnel were made by using established measurement protocols of the USGS (Cunningham and Schalk, 2011). Depths-to-groundwater measurements made by SJGS personnel, SJCM personnel, consultants, or contractors were taken from reports without reference to measurement protocols. Several wells listed in table 1 were used to measure depths to groundwater by USGS personnel prior to 2011. The sources of unique depth-to-groundwater measurements are noted in table 2. USGS-measured depths to groundwater, reported as depth to water below land surface rather than from the well-measuring point, were corrected to land surface by subtracting the height of the measuring point from the depth measurements (tables 1 and 2). USGS-measured depth-to-water data are also available on the NWIS Web site (http://waterdata.usgs.gov/nwis).

Results of the analyses of groundwater-quality samples collected from SJCM and SJGS wells are included in table 3. SJCM digital groundwater-quality records were obtained from the MMD database (http://www.emnrd.state.nm.us/MMD/gismapminedata.html). SJGS groundwater-quality records, obtained at NMED, were transcribed and converted to consistent units as needed (table 3). Depth to water and analytical chemistry data were checked by plotting in time series and also by comparison to various reports. Data determined to be erroneous or otherwise spurious, by graphing, by inspection, or by checking against alternate documentation during the review process, are coded as “SX” in tables 2 and 3.

Surveying Methods and Associated Error

USGS personnel surveyed well-measuring-point locations between 2011 and 2013 by using Global Positioning System (GPS) static and real-time-kinematic (RTK) survey methods. Survey data were processed through the National Geodetic Survey (NGS) Online Positioning User Service (OPUS; http://www.ngs.noaa.gov/OPUS/). Survey base stations were established by using static occupations at each base station for a minimum of 2 hours while recording GPS coordinate data delivered from satellites. Output from OPUS processing of base-station static surveys indicated that horizontal survey uncertainties, in terms of reported root-mean-square error, were less than 0.03 foot (ft) (1.0 centimeter [cm]) and that vertical survey uncertainties were less than 0.09 ft (2.8 cm).

RTK GPS-satellite surveys were performed to identify well-measuring-point altitudes by combining the use of a base station with known coordinates and equipped with a satellite receiver and a radio with a roving satellite receiver in radio communication with the base-station receiver. RTK methods were used to survey well locations within about 3 miles of a survey base station. RTK methods with GPS equipment used for the project may have added as much as an additional 0.1 ft (3.0 cm) of uncertainty in the vertical direction to well-measuring points, according to method-uncertainty information available at the time the surveys were performed.

Static surveys were performed for wells located more than about 3 miles from survey base stations and for wells not present or not included during RTK GPS-satellite surveys. The maximum vertical uncertainty for these well-specific static GPS surveys was less than 0.3 ft (9 cm), although most were less than 0.2 ft (6 cm). A static GPS survey to an NGS benchmark (J 432, http://www.ngs.noaa.gov/cgi-bin/ds_mark.prl?PidBox=GO02060), performed as a quality assurance check of static GPS methods, returned a vertical elevation within 0.15 ft (4.6 cm) of the vertical elevation reported by the NGS.

At locations of paired wells, the accepted static or RTK elevation was assigned to one of the wells, and the elevation of the other well was determined by using a level transit to determine the elevation difference between the measuring points for the paired wells. At the SJGS recovery-trench well cluster, measuring-point altitudes surveyed by level transit were adjusted to the surveyed altitude of the recovery-trench-well pumping well. Level survey methods are expected to reduce the relative uncertainty between measuring-point-altitude differences to less than 0.02 ft (0.61 cm).

References Cited

Cunningham, W.L., and Schalk, C.W., comps., 2011, Groundwater technical procedures of the U.S. Geological Survey: U.S. Geological Survey Techniques and Methods 1–A1, 151 p., accessed 2011–2014 at https://pubs.usgs.gov/tm/1a1/.

Esri, 2004, Geospatial location digital data: Redlands, Calif., Esri.

Metric Corp, 1982, Hydrologic conditions along the Westwater and Shumway drainages, San Juan County, NM: Prepared by Metric Corp for San Juan Coal Company, Waterflow, N. Mex., June 20, 1990, on file at the Mining and Minerals Division of the State of New Mexico Energy, Minerals and Natural Resources Department.

Conversion Factors

Inch/Pound to International System of Units
Multiply By To obtain

Length

inch (in.)   2.54 centimeter (cm)
inch (in.) 25.4 millimeter (mm)
foot (ft)  0.3048 meter (m)
mile (mi)   1.609 kilometer (km)


International System of Units to Inch/Pound

Multiply By To obtain

Volume

liter (L)
liter (L)
liter (L)
liter (L)
liter (L)

33.82
  2.113
  1.057
  0.2642
61.02
ounce, fluid (fl. oz)
pint (pt)
quart (qt)
gallon (gal)
cubic inch (in3)

Mass

gram (g)   0.03527 ounce, avoirdupois (oz)

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 (NAVD 88).
Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).
Altitude, as used in this report, refers to distance above the vertical datum.
Concentrations of chemical constituents in water are given in either milligrams per liter (mg/L) or micrograms per liter (µg/L).

Suggested citation:

Stewart, A.M., and Thomas, Nicole, 2015, Hydrologic data from wells at or in the vicinity of the San Juan Coal Mine, San Juan County, New Mexico, 1973–2013: U.S. Geological Survey Data Series 933, https://dx.doi.org/10.3133/ds933.

ISSN 2327-638X (online)



Back to Index Page

Accessibility FOIA Privacy Policies and Notices

USA.gov logo U.S. Department of the Interior | U.S. Geological Survey
URL: https://pubs.usgs.gov/ds/0933/ds933.html
Page Contact Information: Contact USGS
Page Last Modified: Monday, November 28, 2016, 08:30:51 PM