PROJ00444

• Contract/PO #: C150012
• Contractor Name: Model Land and Irrigation Company, The
• Contract Type: Loan
• Water District: 19
• County: Las Animas
• Bill Number: EIA
• Loan Projects - Doc Type: Feasibility Study

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SECTIONSIX

Investigation and Rehabilitation Measures

The following final design repairs of the dam and outlet works will be performed:

1. Demolition and removal of the existing outlet works, excavation to sound foundation
material below the new outlet works, and placement of a compacted fill foundation below the
new outlet works conduit.

2. Construction of a new outlet works with an intake tower and access bridge, a precast
reinforced concrete pipe outlet (RCP), and downstream headwall.

3. Construction of a new outlet works stilling basin.

4. Construction of upstream slope protection in the vicinity of the new outlet works, consisting
of fabriform mats or reinforced concrete, and to repair areas of the existing slope protection
that have cracked through to the underlying embankment material.

5. Construction of a filter sand seepage collection system to control seepage along the new
outlet works.

6. Flattening the downstream slope of the dam in the vicinity of the new outlet works to 2H:IV.

7. Rebuilding the parapet wall on the dam on the breach section.

The design of these repairs is discussed below.

6.2.1 Outlet Works

The existing tower, portions of the upstream slope slab, and the existing conduit will be removed
in conjunction with excavation required to construct the new structures. A new, reinforced
concrete tower will be built and will utilize the existing four-foot-diameter gate. A four-foot-
diameter RCP, with a reinforced concrete cradle, will extend from the intake structure to a
concrete headwall downstream. A stilling basin with sections of grouted and ungrouted riprap
will extend from the headwall to the unlined existing canal downstream. A temporary diversion
pipe (located north of the existing outlet works centerline) will be used to convey inflows
through the dam during construction.

6.2.1.1 Intake Structure

The intake tower will be a reinforced concrete box structure. The invert of the tower will be set
at El. 5729.5 and the top of the structure will be at El. 5762.0. The existing four-foot-diameter
gate will be located at the bottom of the tower, with a centerline elevation of 5734.0. Three 4'6"
x 4'6" openings with trashracks will be located on the north, west, and south sides of the tower.
The ground elevation around the intake tower will be graded to elevation 5741 to match the
existing stream channel.

The intake structure was sized structurally to provide adequate space for the gate and trashrack
structures and the top of the structure was set at the elevation ofthe top of the parapet wall on the
dam. A Stevens Data Logger will be utilized in the intake structure for water level measurement.
A similar type of logger will be used in the downstream canal, approximately 10 miles
downstream of the dam, for flow measurement.

URS Breiner Wtwdward Clyde

6800044333.OOIR2.doc 11311OO(3:18PM)fPROJECTS 6-2