7046 ‎(2)‎

• UCREFRP Catalog Number: 7046
• Author: Valdez, R. A., W. J. Masslich and A. Wasowicz.
• Title: Final Report\
• USFW Year: 1992.
• Copyright Material: NO

20

I
I
I
I
I
I
I
I
I
il
I
I
I
I
I
I
I
I
I

related to low flows and saline groundwater inflow in Paradox Valley. On Trip 6, conductivity
increased across Paradox Valley, from 784 umbos/em at RM 74.0 to 1820 umbos/em at RM 68.5.

4.3.2.15 Dissolved Oxyeen. Dissolved oxygen in the Dolores River was measured during five of
six trips in 1990-1991, and generally ranged from 7 to 10 mg/L EPA's standards for non-salmonid
fisheries are 6.5 mg/l for early life stages and 6.0 mg/l for all other life stages.

4.3.3 Fish Tissue and Sediment Analysis

4.3.3.1 Sediment Analvsis. Radium (R-226) may be introduced into stream sediments when
uranium mill wastes are released into a stream, either by direct discharge or seepage (Tsivoglou et
al. 1960). Stream sediments act as radium reservoirs, collecting and storing this element. Where
concentrations of most elements decrease with increased stream flow, the release of dissolved radium
from sediments is stimulated by increased velocities and turbulence.

Radium in sediments from the Dolores and San Miguel rivers ranged from 6.2 to 8.0 pCi/g, except
for a concentration of 20.4 pCi/g at RM 59.7, just below tbe confluence of the San Miguel River
(Table 42). Historically, fluctuating but similar levels of radium were recorded in Dolores River
sediment for four study areas from 1960-63 (Table 44). Measurements by BIO/WEST in 1991
showed similar concentrations in three areas, and somewhat higher concentrations in the three
remaining areas. Radium concentrations at RM 0.1 of the San Miguel increased greatly in 1960-63,
but levels in 1991 were substantially lower. In 1960, radium concentrations were measured in
sediments from the Dolores River, above Slickrock, and from the San Miguel River above Naturita.
These concentrations were used as "background levels" of radioactivity in river sediments located
upstream of sources of man-made contamination (PHS 1961). Based on these results, sediment from
three sites on the Dolores River contained from 3 to 3.3 times the amount of background radiation.
The remaining site on the Dolores River measured 9.3 times greater than background levels.
Sediments from the single study site in the San Miguel River were 5.6 times greater than background.
In 1956, Tsivoglou reported concentrations as high as 2,100 pCi/g in the San Miguel River below the
Naturita uranium mill, or 2,100 times background levels (Tsivoglou et al. in Sigler et a1. 1966).

Radium concentrations in sediments of the Dolores and SaD Miguel rivers appeared in a state of
improvement since peak uranium operations in the 1950's. The closure of the Uravan Mill in 1970,
and the subsequent Super Fund clean-up program initiated in 1988, were probably the main reasons
for this improvement. In the 1960's, radium in Dolores River sediments appeared to increase with
distance downstream (Table 41), possibly because of decreased radium inputs (i.e. closure of the mill
in 1970) and gradual movement of existing radium in downstream sediments. No longitudinal trends
were apparent for radium measured in 1991.

Although analysis of heavy metals was not included in the Dolores River sediment analysis, it is
likely that high concentrations of at least certain metals were present since stream sediments may
serve as storage reservoirs and primary sources of bioconcentration (Van Hassel et ale 1980). Mathis
et al. (1979) reported concentrations of cadmium in sediments of an experimental power plant pond
of about 450 times the amount found in the water; lead in sediments was concentrated about 4,000
times that in water.

4.3.3.2 Fish Tissue Analvsis. Eighteen individual fish representing three species were collected
during Trip 6 for tissue analysis (Table 42). Although variance between samples can be high,
maximum metal concentrations within fISh species is a good indicator of potential bioaccumulation
problems in the system. Maximum levels of metals (mglkg) in liver and kidney tissue from three fish