FLOOD03543

• County: Arapahoe
• Stream Name: South Platte
• Basin: South Platte
• Title: Union Avenue Boat Drop
• Date: 1/1/1983
• Prepared For: CWCB
• Prepared By: CWCB
• Floodplain - Doc Type: Easement

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Mr. David W. Walker
October 30, 1989
Page 5

The following calculations are typical of those made and have been included as Appendix
C.
1. Effect of tailwater elevation from the downstream embankment
on the operation of the Englewood intake radial gate.

2. Comparison of flow rate through existing notch in USACE dam
crest with that through proposed boatchute with upstream water
surface set at elevation 5289.5.

3. Preliminary water surface profiles for boating flows with the
proposed boatchutes and embankments.

4. Preliminary water surface profile for the USACE 100-year
discharge of 16,400 cfs with the proposed boatchutes and
embankments.

. 5. Capacity of Englewood intake channel and upstream excavated
channel. Water surface profile for discharge of 100 cfs and a
downstream water surface elevation of 5289.5.

The results of the USBR model test support the following preliminary engineering
conclusions.

1. The tailwater caused by the downstream embankment has no
effect on the sluicing action of the radial gate.

2. During low flows, the first 100 cfs in the river is mostly
allocated to the Englewood intake. The proposed boatchute
has similar flow characteristics as those of the 14-feet wide
notch in the existing dam crest.

3. The proposed boatchute configuration and elevations are
conducive to boating consistent with that established on the
river to date through efforts of numerous agencies. There is no
claim that boating will be safe at Union Avenue, only that
hazards will tend to be reduced from the existing conditions.

4. With the proposed embankments in place within the South
Platte River, the 100-year USACE flood of 16,400 cfs is
contained within the channel both downstream and upstream
of Union Avenue.