WSP06151

• File Number: 8274.400
• Description: Colorado River Basin Salinity Control - General Basinwide Salinity Issues - NPDES
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 9/1/1995
• Author: Applied Hydrology
• Title: Salinity Control Study - NPDES Permit No. CO - 0042161 - Prepared for Twentymile Coal Company
• Water Supply Pro - Doc Type: Report/Study

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NPDES P~rmit No. CO-0042161
Salinity Cpntrol Study

Twentymile Coal Company

4.1.3 O~tion 3: Injection up to 0.5 cfs

Option 3 involves injection of dewatering flows up to 0.5 cfs, and untreated discharge of flow
in excess ~f this, This option is not as effective when discharge tatesexceed the injection
system ca(tacity estimated at 0.5 cfs, but it could be more effective if the uuectionwell proved
capable of: handling more than 0;5 cfs or if the surge storage capacity of the sedimentation
pond were!expanded,

The calculated salt loads and cOncentrations in Fish Creek resulting from Option 3 are
provided In Table 5. The monthly average flows and s31i loads, in the discharge under
Option 3 were added to the average monthly flows and salt loads in Fish Creek upstream of tbe
discharge 'points (Station 16), to estimate monthly flows arid salt loads for Fish Creek
downstrea!n of the discharge. "

Option 3: results in a reduction in average salt loading for the 1990-1994 record of
1.09 tons(lIay. of the total dewatering load of 1.83 tons/day. Like Options 1 and 2, this does
not substap.tially change the salt load in Fish Creek downstream of the discharge. A reduction
of 1.09 tops/day would decrease the average daily salt load in Fish Creek from 8 to 12 \lercent
in the 1990-1994 record. '

Option 3: would reduce IDS concentrations in Fish Creek downstream of the discharge,
although less so than for Options 1 arid 2. Table 5 shows average IDS concentrations
downstr$ of the mixing zone for the discharge outfall would decline from 781 ppm to 565
'ppm. Si(lce the average IDS concentration in Fish Creek at Station 302 downStream of the
dischargetoutfall is 685 mg/I for 1990-1994, Option 3 would reduce IDS concentrations in
Fish Creek from 18 to 28 percent.

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