DO Improvement Feasibility Study
Salt Creek 6.0 Evaluation
DRSCW 6-4 September 2009
TABLE 6-1
SALT CREEK POTW UPGRADE ESTIMATE
CAPITAL COST FOR MBR & GAC ADDITIONS
Plant Design Average Design Max MBR GAC Per Plant
Flow, MGD Flow, MGD @ $2/Gal @ $1.50/Gal Total
Egan 30.00 50.00 $100,000,000 $75,000,000 $175,000,000
Nordic Park 0.50 1.00 $2,000,000 $1,500,000 $3,500,000
Itasca 2.60 10.00 $20,000,000 $15,000,000 $35,000,000
Wood Dale N 1.97 3.93 $7,860,000 $5,895,000 $13,755,000
Wood Dale S 1.13 2.33 $4,660,000 $3,495,000 $8,155,000
Addison N 5.30 7.60 $15,200,000 $11,400,000 $26,600,000
Addison S 3.20 8.00 $16,000,000 $12,000,000 $28,000,000
SC SD 3.30 8.00 $16,000,000 $12,000,000 $28,000,000
Elmhurst 8.00 20.00 $40,000,000 $30,000,000 $70,000,000
$388,000,000
6.3 Alternative 2: Dam Crest Drop or Bridging (Graue Mill Dam) and
Removal (Oak Meadows Dam)
Alternative 2 was prepared, assuming dam removal in the case of Oak Meadows, and the
lowering of the Graue Mill Dam by 1 ft, 2 ft, and 3 ft. Figure 6-3 presents the minimum DO
profile under the various dam removal/bridging options, along with the baseline DO profile. The
model predicts the minimum DO above Oak Meadows will still decline to below 4.0 mg/L. This
is a location where additional monitoring data would be appropriate. The model predicts that this
drop in DO happens nearly 2.5 River Mile (4 km) above the Oak Meadows Dam. This output is
suspect, as there is a wastewater treatment plant discharge (the Itasca POTW) at River Mile 25.7
(km 41.4 km), or 2.8 miles (4.5 km) above the Oak Meadows Dam. More recent DO data from
the Itasca POTW indicates a minimum DO effluent level of 6 mg/L, and one would expect some
distance before 5.0 mg/L would be reached. In addition, this POTW is currently undergoing a
significant upgrade that will result in a higher quality effluent than is currently being attained.
Below this wastewater treatment plant there is excellent canopy cover until the Oak Meadows
Golf Course, conducive to minimizing algal growth. Only two SOD results have been collected
above the Oak Meadows Dam at River Mile 23.0 and 22.9 (37.0 and 36.8 km), one a low 0.5
g/m2/day and the second 2.27 g/m2/day. The model used the highest of these two values, which is
likely unrepresentative of the average SOD conditions.
At the Graue Mill Dam, lowering the crest one foot improves the minimum DO to 4.0 mg/L
(from 1.2 mg/L), and lowering the crest two feet improves the minimum DO to 5.2 mg/L. If the
crest is lowered three ft, the minimum DO is predicted to remain above 6.0 mg/L. Thus, a
reduction in crest height of 2 ft at the Graue Mill Dam would result in achieving the Illinois DO
