October 2009 - South Tahoe Public Utility District

season when ample water is available for diversion. The Alpine Decree mandates that a water
right can not be diverted from the river at a rate greater than 40% per month; this is known as
the 40:40:20 diversion rate.
The conceptual cost of piping the distance from the West Fork of the Carson River to the
Harvey Channel, approximately 10,500 feet, is $3.0 million.
Alternatively the existing ditch could be enlarged in place with short piped sections for areas
where erosion and steep hillside locations. This would reduce the capital cost but operation and
maintenance costs would continue and seepage in the ditch would persist.
Finally, if the C-Line extension to bypass Harvey Place Reservoir were constructed, the
abandoned portion of the C-Line (see Figure 9.1 at the end of Section 9) could be utilized for
Snowshoe Thompson No. 1 flows. Construction of two short connector pipelines between the
Ditch and the aforementioned section of C-Line would be the only additional infrastructure
required.
11.1.2 Project Considerations
Constructability of the pipeline in its existing alignment is a major hurdle to the completion of this
project. The side hill that the alignment runs along is steep and unstable. Traditional open
trench methods may need to be modified in order to use the existing alignment. There are
several environmental concerns addressed in the Environmental Impact Report that may dictate
the construction schedule.
11.1.3 Phase 1 – Diversion to Highway 89
Phase 1 of the Snowshoe Thompson No. 1 reconstruction is planned to commence at the head
works of the split of Millich Ditch. The existing concrete structure will be modified to incorporate
a debris screen and gate. Phase 1 reach totals 2,900 linear feet that is planned to be replaced
with 36-inch diameter pipe. Periodically along the alignment sediment sumps should be
constructed to aid in pipeline maintenance. Prioritizing construction of Phase 1 is important to
minimize the District‟s operational constraints during high runoff events, and convey the
maximum allocated volume of water to Indian Creek Reservoir.
11.1.4 Phase 2 – Highway 89 to Upper Dressler Ditch
Phase 2 improvements are less critical than the upstream Phase 1 reach. The existing capacity
is less hindered throughout this reach; however transmission losses are quite high. Phase 2
improvements includes approximately 8,700 linear feet of ditch conversion to 36-inch diameter
pipe. Alternatively, the abandoned portion of C-Line could be utilized for Snowshoe Thompson
No. 1 flows, considerably reducing the Phase 2 improvements.
11.2 Project No. 15 - Upper Dressler Ditch Conveyance
Improvements
This project addresses the purpose and need statement:
PN-9. Ability to meet Indian Creek Reservoir water quality requirements is impaired and
the District needs to meet TMDL requirements for the Indian Creek Reservoir.
South Tahoe Public Utility District
Recycled Water Facilities Master Plan - October 2009 Page 11-82