WSP01548

• File Number: 8220.106
• Description: Animas-La Plata
• State: CO
• Basin: San Juan/Dolores
• Water Division: 7
• Date: 7/1/1987
• Author: EPI
• Title: An Analysis of the Animas-La Plata Project - Durango-Colorado - July 1987
• Water Supply Pro - Doc Type: Report/Study

~ i

Reservoir.

The DPR indicates "the fate of heavy metals in Ridges Basin
Reservoir is dependent on thermal stratification, dissolved
oxygen depletion in the hypolimnion, water chemistry, heavy
metals retention, and sediment-water interface geochemistry
in the reservoir". .

The best discussion of water quality problems in the project
area can only be found in the DPR Water Supply Appendix.
This Appendix indicates countless instances of where water
quality standards were exceeded in test samples taken for
the project. The following are such examples for the Animas
River:

The total and dissolved manganese concentrations of
the water quality samples taken at Durango average
142 ug/L and 130 ug/L, respectively. The EPA maximum
advisable secondary drinking water criteria for
dissolved manganese is 50 ug/L.

';'

The dissolved form of this metal could cause
aesthetic problems to domestic water users such
as unpleasant taste and odor. stainina of plumbina
fixtures. and deposits on food durina cookina
<emphasis added).

~l
;~ :

Cadmium concentrations in the river at Durango
exceed both drinking water standards and aquatic live
criteria at times. Total concentrations in the eight
samples taken in 1977 and 1978 averaged 24 ug/L of
which about 4 ug/L was dissolved.

The National Interim Drinking Water Standard for
cadmium is 10 ug/L. The aquatic life criteria ranges
from l.2 to 12 ug/L for various hardnesses of water.
For agricultural use 10 ug/L is the recommended
criteria. The available data show the recommended
limits for domestic agriculture, and aquatic life
have all been exceeded at times.

.
"'.

;~
.'
~.-
,
f'
"

i:,_
/,
,~
,;J
,~? i
1ri
;i;
r~'
;1:
{":

The picture of the La Plata River is not much different.
According to the DPR:

In summary, the water quality of the La Plata River
at Farmington has been drastically affected by man's
uses. Irrigation has had the major impact with metal
mining secondary. The dissolved solids and cadmium
content could limit agricultural and domestic uses.
The aquatic community is mainly limited by extreme
variations in flow, which seem to overshadow the
chemical characteristics.

33