C153773 Feasibility Study

• Contract/PO #: C153773
• Contractor Name: Morrison, Town of
• Contract Type: Loan
• Water District: 9
• County: Jefferson
• Bill Number: HB 95-1155
• Loan Projects - Doc Type: Feasibility Study

I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I

-
-

opposite bank through a large boulder drop chute. Although the diversion structure on Bear
Creek is presently serving the water needs of Morrison, a more permanent structure could be
constructed to improve water intake reliability.

The intake system consists of a headgate control gate, grit chamber and manhole-type inverted-
cone sand trap. The grit chamber is a 12-foot diameter circular concrete pipe located
approximately 150 feet downstream of the intake. Frequent problems with icing of the intake
occur during the winter. An old lO-inch steel water line, constructed many years ago, conveys
the water approximately 800 lineal feet from the sand trap to the stilling basins. This line
includes a tunnel section of about 75 feet in length. This entire intake pipe section is in poor
condition and will need to be rehabilitated if the existing gravity intake system is to be
maintained.

The stilling basins consist of two bays of masonry-concrete construction. These basins are in
very poor condition and leak a considerable amount of water, but they have been functional.
Because the bays are located in the shady north side of the valley, winter freezing problems are
pronounced.

The reach from the intake on Bear Creek through the stilling basin was identified as the most
critical reach needing to be replaced. In 1985, McLaughlin Water Engineers prepared plans and
specifications for a new intake, pipeline and grit chamber"). The design was 90% complete;
however, due to funding constraints and indecision by the Town to continue rehabilitating the
gravity intake system (as opposed to constructing a new pump intake nearer the water treatment
plant), the project was never constructed. The design included a 24-inch intake pipe to provide
adequate capacity for the proposed service needs of Mt. Carbon, with Morrison's and Mt.
Carbon's water rights. Since the time of the design, negotiations have been finalized on
Morrison's water augmentation plan and the contract with Mt. Carbon has been broken. If
Morrison chooses to pursue rehabilitation of the intake line, the design can be downsized to
more economically meet realistic future water needs.

Downstream of the stilling basin is approximately 3,OOO-foot of transmission line from the stilling
basin to the water treatment plant. The alignment of the pipe follows the natural contours along
the steep hillsides and includes two spans across gullies and narrow paths across rock outcrops.
This line was originally constructed with thin-walled 10-inch steel pipe; but in 1961 it was
replaced with 12-inch mortar-lined cast iron pipe (CIP). It would be an expensive proposition to
replace this pipe, and continued use of the gravity intake is feasible if this section of pipe has

70-080.035:MSTR-PLN

II-9