WSP10769

• File Number: 8220.105
• Description: Colorado River-Water Projects-Navajo
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 7/1/2001
• Author: BOR
• Title: Revised Draft Environmental Assessment for the Jicarilla Apache Nation Water Subcontract-aka USBR/PNM Water Contract Renewal and Extension
• Water Supply Pro - Doc Type: Report/Study

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6.2.1.3 Current Conditions

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Since May 1983, SJGS has operated as an NPDES permitted zero liquid discharge facility. All
wastewaters are pumped to lined solar evaporation ponds, and no wastewater leaves the facility except
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6.2.2 Stream now Regime

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The two principal tributaries flowing past the SJGS into the San Juan River are the Shumway and
Westwater Arroyos. Both flow through the facility property and south to the San Juan River. The San
Juan River is the major hydrologic feature of the area, and is the site of the SJGS weir and diversion
structure.

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6.2.2.1 Shumway Arroyo

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The Shumway Arroyo is an ephemeral stream that flows principally in response to rainfall. North ofSJGS
it is an ephemeral stream and becomes intermittent between the storage reservoir and the San Juan River.
At the lower end, where it crosses through irrigated fields, it carries irrigation return flows during the
growing season and occasionally ground-water seepage resulting from snowmelt in the winter and spring.

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The State of New Mexico Environment Department collected benthic macroinvertebrate samples on
December 16, 1993 from Shumway Arroyo at the point where it intersects with the SJGS access road.
The analysis resulted in the identification of 149 organisms in 21 taxa; the majority of taxa were dipterans
(true flies). In addition, a sensitive taxon, the stone fly Cullis aeslvalis, was collected. The sample
analysts determined that the diversity represented by the 1993 sample sharply contrasted with the paucity
of specimens in collections from the same location in April 1982.

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Water samples were collected in June 1994 and sediment samples were collected in August 1994 by PNM
for analysis of metals and polycyclic aromatic hydrocarbon (PAH) content. Samples were collected from
below the storage reservoir, in Westwater Arroyo, Shumway Arroyo. and the San Juan River. Those
samples were analyzed using standard U.S. Environmental Protection Agency analytical protocols.
Metals were detected in all sediment samples, although selenium, arsenic, and mercury were not detected
in any samples. Metal concentrations generally ranged from relatively low in the Westwater Arroyo to
relatively high in the San Juan River, both above the SJGS weir and below the mouth of Shumway
Arroyo. No P AHs were detected.

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Concentrations of metals in water were generally low. Concentrations of calcium, iron. sodium, and
nitrates were elevated in water collected from immediately below the storage reservoir, although not
above water quality standards. The water below the storage reservoir is pumped from a point
approximately 30 feet below the sample location back to the reservoir. Therefore, these constituents do
not reach Shumway Arroyo or the San Juan River. Constilllents in water samples collected approximately
1.5 miles downstream in Shumway Arroyo were similar in content to the remaining Shumway Arroyo
and San Juan River samples.

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Because selenium, arsenic. mercury, and P AHs were not detected in the samples analyzed with standard
methods, additional sediment and water samples were collected by PNM from four locations in January
1995 to be analyzed for those constituents. The samples were collected from Westwater Arroyo,

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