BOARD01603

• Board Meeting Date: 9/13/2004
• Description: CF Section - Changes to Existing Loans - East Fork Mutual Irrigation Company Ditch Rehabilitation
• Board Meetings - Doc Type: Memo

~

portion of the ditch. These slope failures were most likely caused by ditch flows saturating the surrounding __
soil and becoming perched on top of the underlying bedrock layer, and the surcharge of the fill on the
downhill side of the ditch.

In the swnmer of 2003, the Company was in jeopardy oflosing a significant portion of their ditch.
In an attempt to address the problem the Company elected to enclose 1,060 linear feet of ditch where the
two slope failures had occurred, with 60-inch corrugated steel pipe. Additionally, to stabilize the slope
failure areas the Company installed soil nails to restrict the failed areas from migrating any further.

In the fall of 2003 the Company hired the services of Northwest Colorado Consultants, Inc.,
Steamboat Springs, Colorado, to evaluate the slope failures, the improvements in-place, and to make
recommendations on how to stabilize the ditch on a long-term basis. In December of 2003, Northwest
Colorado Consultants completed a feasibility study to address these problems, which was submitted to the
Colorado Water Conservation Board in January of 2004 for funding consideration. The report
recommended that the existing 60-inch corrugated steel pipe be modified with water tight bands, concrete
headwalls be constructed on the upstream and downstream end of the pipe to minimize water flow under
the pipe, failed slope areas be regraded and revegetated, and the exposed soil nails be covered with
shotcrete.

Table 1 below is a brief swnmary of the major project elements and their estimated cost as
presented in the original feasibility study:

Table 1. Project Cost Summary

e

Item Estimated Cost
1. 1,060 1.f. of60-inch CSP (already constructed) $63,924
2. Soil Nailing (already constructed) $38,000
3. Water Tight Joint Bands $83,125
4. Concrete Headwalls (liJ Inlet/Outlet $20,000
5. Shotcrete Soil Nail Areas $18,000
6. Remove/Regrade Failed Slope Areas $92,000
7. Revegetation and Erosion Control $18,000
Subtotal: $333,049
8. Engineering $10,000
Total: (Completed Proiect) $343,049

Since the Board's approval of these improvements in January of 2004, the Company has had
concerns over the long-term performance of the failed slope remediation efforts proposed by Northwest
Colorado Consultants. Given the severity of the problem and the significant hardship and monetary loss
that the Company would incur if another failure would occur, the Company elected to obtain a second
engineering opinion on the failed slope areas.

In the spring of 2004, the Company hired the services of Kumar and Associates, Denver,
Colorado to evaluate the slope failure areas and to prepare an alternative analysis to address the
problem. Kumar's efforts involved exploratory borings and field reconnaissance of the surface and e
subsurface to determine the condition of the soils within the failed slope areas. Based on their soil
findings and field survey, Kumar recommended that stabilization measures be taken at the head ofthe

2
Flood Protection. Water Project Planning and Financing. Stream and Lake Protection
Water Supply Protection. Conservation Planning