October 2009 - South Tahoe Public Utility District

Section 4: Existing Recycled Water System
4.1 Recycled Water Facilities
The existing recycled water facilities for the District‟s operations include the South Lake Tahoe
Wastewater Treatment Plant (WWTP), A, B and C-Line Export Pipelines, the Harvey Place
Reservoir, the Diamond Ditch, contract irrigator application sites, and the On Farm emergency
disposal site.
Each of these facilities is essential for the operation of the recycled water distribution system.
The recycled water facilities capacity and condition assessment is provided in Appendix C -
Hydrology and Hydraulics Review.
4.1.1 General System Description
The A-Line and B-Line export pipelines convey recycled water from the South Lake Tahoe
WWTP to the top of Luther Pass. The C-Line extends from the top of Luther Pass to Harvey
Place Reservoir located to the south of Diamond Valley in Alpine County (See Figure 4.1 at the
end of Section 4). The Diamond Ditch carries recycled water from Harvey Place Reservoir to
irrigated lands in Wade Valley and along Hwy 88 west of the West Fork of the Carson River.
Several irrigation laterals distribute the recycled water throughout the application areas.
Although the recycled water conveyance and application areas extend to the Nevada state line,
the District responsibilities and facilities end at the two junction boxes across Chambers Lane
on the west side of the river at the Paynesville Bridge. From the Paynesville Bridge all recycled
water is the responsibility of the various land applicators.
4.1.1.1 Harvey Place Reservoir
Harvey Place Reservoir, constructed in 1989, has an active storage capacity of approximately
3,800 acre-feet. The actual storage capacity of Harvey Place Reservoir is approximately 4,000
acre-feet, but 200 acre-feet lies below the outlet of the reservoir (CWC-HDR, 1988). The
elevation of the primary spillway on Harvey Place Dam is approximately 5,563 feet above sea
level, which corresponds to the maximum elevation water should rise to during normal
operation. The District‟s normal operation is to fill the reservoir with recycled water from
October 15 to April 1, without any discharge. After April 1, the District may begin drawing the
reservoir to minimum pool before October 15 to allow for it to be filled again during the winter
(CWC-HDR, 1988).
4.1.1.2 Diamond Ditch System
The Diamond Ditch system begins at the outlet works of Harvey Place Reservoir. The Ditch
runs parallel to the Harvey Place Reservoir access road then crosses under Diamond Valley
Road and Indian Creek in a double-barrel inverted siphon. The inverted siphon is located in
Diamond Valley just upstream of a short narrow canyon that connects Diamond Valley to Dutch
Valley. The capacity of the Diamond Ditch and inverted siphon under Indian Creek, as reported
in the District‟s Operation and Maintenance Manual, is 40 cfs (CWC-HDR, 1988); however, two
choke points limit the capacity of the Diamond Ditch to approximately 20 cfs. One choke point is
located at Bar Screen No. 3 near where Snowshoe Thompson No. 2 Ditch terminates at the
Diamond Ditch, and the other choke point is located at Bar Screen No. 5 at the box where flow
transitions from open channel to pipeline flow for the existing pipeline that leads to the
South Tahoe Public Utility District
Recycled Water Facilities Master Plan - October 2009 Page 4-19