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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SECTION THREE

Project Description

3.3 OPERATING CRITERIA

Black Hills Reservoir has recently been primarily used for regulating diversions from the
Purgatoire River, for flood detention, and as supplemental storage when John Martin Reservoir
has filled and there is excess water in the Purgatoire River. The availability of excess water for
supplemental storage has been infrequent. The Company plans to repair the dam to reestablish
its function as a regulating facility critical to downstream irrigation and farming. The repairs
would restore storage up to gage height 20, which corresponds to an approximate storage
capacity of 4,000 to 5,000 acre-feet. The reservoir has been operating up to gage height 20
since the spillway was constructed in 1986, with the exception of the October 1998 zero storage
restriction.

Operational flow releases for irrigation under normal operating conditions ranges from 30 to 75
cubic feet per second (cfs) with occasional releases up to about 110 cfs. Based on discussions
with the Company, the existing outlet works operating range is suitable for their irrigation
practices.

Repair of the dam will also include re-establishment of some of the outlet works capacity that
was lost when the existing gate was installed approximately 14 feet above the original intake
level. The outlet works capacity for the repaired dam will be a minimum of250 cfs at gage
height 20.

3.4 FACILITIES AND SERVICE AREA

The Company owns and operates a headgate on the Purgatoire River located approximately five
miles northeast of the City of Trinidad, which is used to divert water into the Model Ditch. The
Company also operates the Model Ditch. The Model Ditch has a capacity of approximately 200
cfs and is approximately 29 miles long. The ditch runs in a northeasterly direction from the
Purgatoire River to the lands irrigated by the ditch.

The Black Hills Reservoir is filled from the Model Ditch. The reservoir is approximately 17
miles downstream of the headgate. The ditch discharges directly into the Black Hills Reservoir,
and the reservoir discharges back into the ditch. The ditch then extends an additional 12 miles
from the reservoir to the irrigated lands. There is no facility to bypass water in the ditch around
the reservoir. There are approximately 6,180 irrigated acres supplied by the ditch. The locations
of the Model Ditch, the Reservoir, and the company's facilities and irrigated lands are shown on
Figure 3-3.

3.5 SURVEYING

Peterson Surveying, Inc. of La Junta, Colorado performed surveying in January and October of
1999 in the vicinity of the outlet works for use in repair and rehabilitation designs of the dam.

The survey utilized the Global Position System and tied into the USGS benchmark at the
northeast comer of Section 24, Township 31 South, Range 63 West, Las Animas County,
Colorado. The survey also included the spillway constructed in 1986 with a cross-section along
the dam crest alignment and a profile along the spillway centerline. The dam embankment was
cross-sectioned at 100 foot increments for 500 feet on either side ofthe existing outlet works.

URS Breiner Woodward Clyde

6800044333.OOIR2.doc 11311OO{3:18 PM)/PROJECTS 3-4