October 2009 - South Tahoe Public Utility District

9.4.1 Project Description
The design objective of this pipe network is to have one pipeline to convey recycled water or
freshwater from the Harvey Place Reservoir outlet facility to the irrigation fields for irrigation of
the irrigation fields and potentially other portions of the Diamond Valley Ranch. The Harvey
Place Reservoir /Irrigation Field Connection Pipe Bypass Pipeline would convey recycled water
from Harvey Place Reservoir to irrigate the irrigation fields and would provide recycled water to
irrigate other lands in Diamond Valley. From this trunk system distribution pipelines branch and
take irrigation water to the north and south corners of the irrigated lands in Diamond Valley. The
trunk system provides flow and pressure to multiple smaller irrigation zones. The irrigation
distribution system should be designed to maximize the use of gravity conveyance. Figure 9.2
(located at the end of Section 9) shows the preliminary configuration of the irrigation distribution
network. This irrigation network provides water for both sprinkler and flood irrigation methods.
This project also includes irrigation of the area known as the “jungle” which is located southeast
of the junction of Highways 88 and 89. The irrigation system planned includes spray irrigation of
the jungle within District property by utilizing a header pipe running along the jungle ridge line
which is connected to the Diamond Valley Ranch irrigation supply pipeline. The irrigation area is
approximately 140 acres. It is not intended to grow crops in the jungle and implementation of
this aspect of Diamond Valley Ranch irrigation would only be utilized if additional application
lands are needed. If jungle irrigation is implemented the conceptual cost for the project is $2.9
million.
9.4.2 Project Considerations
Future phasing is a major consideration for the implementation/installation of the Diamond
Valley irrigation distribution system. Initially the system is planned to distribute freshwater over
the irrigation fields area, however some recycled water may be supplied for irrigation based on
other factors once an application permit is secured from the Lahontan Regional Water Quality
Control Board. The volume of recycled water used in Diamond Valley depends upon the amount
of recycled water required for contractor irrigators. The amount of freshwater used in irrigating
Diamond Valley can make up any shortfall in available recycled water needed.
Because the southeast edge of the Diamond Valley Ranch abuts to Indian Creek, an effective
tailwater control system would have to be implemented.
Special operational considerations may need to be addressed when using pipelines for both
freshwater and recycled water delivery; for example, the ability to completely drain the line when
switching between the two uses. Although the majority of the land initially receives freshwater
irrigation, the District should pursue Lahontan Regional Water Quality Control Board recycled
water application permits for lands in the Diamond Valley. (See Project No. 12, page 10-77).
9.4.3 Phase 1 – Irrigation Fields Irrigation
The first phase of the Diamond Valley Irrigation distribution system construction may be to
convey water to the irrigation fields for irrigation from the Harvey Place Reservoir outlet facility
via the Diamond Valley Pipeline and the Harvey Place Reservoir /Irrigation Fields Connector
pipeline. The initial purpose of this line is to provide freshwater irrigation to the irrigation fields.
Costs associated with the construction of this section of pipe are contained in Section 9.2 -
Harvey Place Reservoir Bypass System Pipelines.
Irrigation of the fields, utilized for times when temporary storage is not needed, assumes that
pipe pressure is adequate to distribute irrigation flows to the entire area. It is estimated the cost
South Tahoe Public Utility District
Recycled Water Facilities Master Plan - October 2009 Page 9-67