BOARD00603

• Board Meeting Date: 9/10/1975
• Description: Agenda or Table of Contents, Minutes, Resolution
• Board Meetings - Doc Type: Meeting

the Regional Engineer; Willis Irwin, Regional Supervisor of Land and
Water Operations; George Stapleton, Public Affairs Officer and Dick
Eagen. the Regional Environmental Officer.

I believe the best place to start on the current status is about
December of '74. That is when the discussion was held with the Lower
South Platte Water Conservancy District and Mr. Sparks about a diffi- I
culty that we were evaluating. That had to do with hydrology and the
transposition of the 1964 Montana storm into this drainage basin and
its effect then upon the cost of the structure.

In that particular meeting, we reached agreement on two counts: one,
that the Bureau of Reclamation would re-evaluate the storm itself and
the resulting flood, and the design of the dam that resulted from that
flood. Secondly, a decision was reached to hire an independent con-
sultant to evaluate the same thing.

Since then, we have been working concurrently with the consultant and
with other entities, one of them being the Corps of Engineers. We
asked them what they thought about the transposition of the storm.
They agreed with that, as did the Weather Service. They suggested some
additional study in the areas of infiltration rate and some other
technical factors, all of which have been considered up to now.

The Dames & Moore report was completed. They also agreed with the
transposition of the storm, but they reduced the flood considerably by
increasing the infiltration rate and some additional retention and
flood retarding structures. They also considered some additional non-
contributing areas.

The Bureau was evaluating concurrently with these other entities this
situation. one the basis of this, I would like to show you now what
the current plan is.

After all the analysis and the inputs, all of which were very good, as
far as the resulting flood is concerned we are probably within ten
percent of the consultant's analysis now. All of the input from the
Corps and the consultant and others has been very helpful in determin-
ing the most rational level of this flood and the resulting cost of
the project. There is not a great deal of difference in the physical
data that we have been operating with before. The height of the dam
is about a foot higher, a hundred and forty-seven feet above the stream
bed. The other pool elevations which basically sit at the top of the
joint use pool is at 44.3. We have two gates now twenty-five feet by
thirty-nine and a half feet, a service and auxiliary spillway and the
resulting pools - flood pool, a joint use pool, active conservation
pool and a dead pool.

I

When all is evaluated, we come up with a total cost of this structure
and this project of about $139,000,000. We have considered all the
inputs, including the one by your consultant. We have modified the
project accordingly. At this time, the project is feasible with a
benefit-cost ratio of about 1.5 to 1. The cost is within the authorized

-2-