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<br />002257
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<br />at the emergency spillway, elevation 256 acre feet (315,776 m3) for
<br />sediment and 1,828 acre feet (2,254,838 m3) for floodwater. The Rock
<br />Creek Floodwater Retarding Structure (east of Superior and south of the
<br />Denver-Boulder Turnpike) is a class C structure with 5 square miles (13
<br />sq. km) of drainage. It is a 48.5 feet (14.8 m) high dam with 731 acre
<br />feet (901,689 m3) of storage at the emergency spillway elevation, 97
<br />acre feet (119,650 m3) for sediment, and 634 acre feet (782,039 m3)
<br />for floodwater. Construction cost for these two structures is $4,500,000
<br />($3,000,000 for Coal Creek and $1,500,000 for Rock Creek). Engineering
<br />(14%), Project Administration (17%), and Land Rights have not been added
<br />to this. These two structures would have very little effect on Erie,
<br />because of the amount of uncontrolled watershed between them and is not
<br />considered feasible.
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<br />Al ternative #2 is a Floodwater Retarding Structure northeast of Lafayette
<br />on Coal Creek. It is a class C structure with 72.3 square miles (189 sq.
<br />km) of drainage. It is a 60.3 feet (18.4 m) high dam with 8,434 acre feet
<br />(10,403,339 m3), of storage at the emergency spillway elevation, 740 acre
<br />feet (912,790 m3) for sediment and 7,694 acre feet (9,490,549 m3) for
<br />floodwater. Construction cost for this structure is $4,405,700. Engi-
<br />neering (14%), Project Administration (17%), and Land Rights have not been
<br />added to this. This alternative is not considered feasible.
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<br />Alternative #3 is a Floodwater Retarding Structure south of Erie on Coal
<br />Creek. It is a class C structure with 76.3 square miles (198 sq. km) of
<br />drainage. It is a 53.3 feet (16.2 km) high dam with 8,300 acre feet
<br />(10,238,050 m3) of storage at the emergency spillway elevation, 782 acre
<br />feet (964,597 m3) of sediment, 7,518 acre feet (9,273,453 m3) of
<br />floodwater. Construction cost for this structure is $4,512,400. Engi-
<br />neering (14%), Project Administration (17%) and Land Rights have not been
<br />added to this. This alternative is not considered feasible.
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<br />Alternative #4 is a Floodwater diversion dike on the east side of Erie.
<br />This alternative also includes clearing and grubbing out 26 acres (10.5
<br />haY of Coal Creek, enlarging the channel between the Perry,Street highway
<br />bridge and the Union Pacific Railroad bridge, building approach ramps to
<br />the dike on Briggs Street, and lengthen the Union Pacific Railroad bridge
<br />from 100 feet (30.5 m) to 200 feet (61 mI. The dike varies from 0 to 7.3
<br />feet (2.2 m) in height. It has a 10 foot (3.0 m) crown with 4:1 side
<br />slopes. This dike will collect the Coal Creek runoff and convey it east
<br />of Erie to the north where it remains in its present floodplain. Total
<br />installation cost is $380,200 which includes $133,500 for construction
<br />cost, $18,700 for engineering, $22,700 for project administration,
<br />$130,400 for railroad bridge, $300 for county road approaches, $10,200 for
<br />land, and $64,400 for relocation. Of the total cost it is estimated that
<br />the PL 566 share-will be $203,200 and the local share will be $241,400.
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<br />Al ternative #5 is flood proofing, which consists of a concrete wall around
<br />each business or residence. Cost estimates for the floodwall are based on
<br />an average of 9 feet (2.7 m) high concrete wall embedded 3.5 feet (l.lm)
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