GENERAL32251

• Permit No: C1989074
• IBM Index Class Name: General Documents
• Doc Date: 8/31/1990
• Doc Name: Proposed Decision & Findings of Compliance for a New Permit
• Permit Index Doc Type: General Correspondence
• Media Type: D
• Archive: No

VI. Hydrologic Balance: Groundwater - Rules 2.04.3, 2.04.7, 2.05.3(4),
an
Regional baseline groundwater hydrology information is presented in
Section 2.04.7(d) of the permit application, Three water-bearing iithologic
units have been identified in the permit area and hydrologically adjacent
areas. These are the Raton Formation, Vermejo Formation, and
Trinidad Sandstone (youngest to oldest).
According to the U. 5. Geological Survey the Trinidad Sandstone is the most
significant aquifer of regional extent in the area, consisting of tightly
cemented sandstone. It has been reported to yield from 0.5 to 5.0 GPM from
wells in the Raton Basin. Water quality is poor to fair and use is primarily
for livestock watering, limited domestic purposes, and irrigation. The
coefficient of permeability is estimated to be less than one darcy. The
Trinidad sanastone is located approximately 80 feet stratigraphically below
the coal seam to be mined. The Raton Formation overlies the
Vermejo Formation. The Sopris Seam, the uppermost seam of the Vermejo
formation, is generally regarded as the formational contact.
The Vermejo Formation which overlies the Trinidad Sandstone contains the coal
seam which is to be mined by the operator. The Vermejo Formation consists
mainly of sandstone and coal lenses interbedded with shale. It has a reported
ground water yield of 0.5 to 2.0 GPM. The water quality is generally rated as
poor and unsuitable for human consumption. The water is mainly used for
livestock and irrigation. This assertion was supported by water quality data
supplied to the Department of Health during the NPDES permit application,
The regional hydrologic study performed by the U.S. Geological Survey
(USGS WRI 83-132) treats the Trinidad Sandstone, the Yermejo and the
Raton Formations together as one bedrock aquifer. The Raton Formation, which
overlies the Vermejo Formation and the coal seam to be mined is not a water
bearing unit at the site. This was demonstrated by the exploratory drilling
performed by the applicant which showed no signs of water from the formation.
Because of their permeability and proximity to the coal seam to be mined, the
Trinidad and Vermejo Formations are the water bearing formations of concern
with respect to mining and reclamation impacts.
A reconnaissance level survey of springs, seeps and mine discharges within
one mile of the permit area was conducted. One seep (the Montoya seep) and
two mine discharges from old mine workings were identified in the northwest
and southeast areas of the permit area, Water quality and flow rates were
measured for the months of April and May. The Montoya seep which originates
from previously undermined area had insufficient volume to evaluate but the
other two mine discharges were checked for temperature, conductivity and pH.
The water quality has been characterized by the applicant to be of poor
quality as demonstrated by the high levels of Total Dissolved Solids (TOSi.
This information can be found in Section 2.04.7(2) of the permit application.
These are the only known discharges of ground water in the permit area.
Further discussion of the potential impact of the operation on groundwater in
the area is given in Section IX of this Findings Document. The two mine
discharges and the seep will be monitored quarterly to determine if they are
impacted by the surface mining operations.
The proposed operation is in compliance with the requirements of this section.
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