October 2009 - South Tahoe Public Utility District

move impounded water from the irrigation fields to the outlet of Harvey Place Reservoir for
redistribution, a pump-back system would be necessary (See Project No. 3, page 9-65).
In order to maintain the aesthetics of Diamond Valley the flood irrigated irrigation fields would
consist of irrigated pasture bounded by embankments. These embankments would serve to
impound the emergency stored water on the irrigation field until it can be transferred back to
Harvey Place Reservoir or to direct land application areas. The configuration of this facility
reflects the natural topography of the area to the greatest extent possible. However, this
configuration is conceptual and detailed facility planning will identify the best location, size and
configuration on the Diamond Valley Ranch.
Project No. 1 pertains to the irrigation fields only. The pipe and ditch improvements are
presented in Section 9.2, Project No. 2 (page 9-63) and the associated pump back facility for
returning flow from the irrigation fields to Harvey Place Reservoir is presented in Section 9.3,
Project No. 3 (page 9-65).
9.1.1 Project Description
The two irrigation fields utilizing surface irrigation methods and serving as emergency,
temporary storage areas would have of gradual embankments of six foot height separating and
surrounding the two fields the two fields. The location of the surface irrigated irrigation fields is
on the western edge Diamond Valley Ranch as shown in Figure No. 9.1 at the end of Section 9.
Field No.1 is approximately 24 acres in size and Field No. 2 is approximately 25 acres. An
average water depth of 6 feet results in approximately 294 acre feet of temporary storage which
at the current treatment plant flow rate of 4.1 MGD equates to approximately 23 days of
temporary storage.
The embankments are planned to be low-sloping berms which allow crop harvesting with
conventional equipment. The design principle guiding this project intends to preserve the
aesthetics of the area by creating natural looking temporary storage boundaries and sloping
embankments which would be used for pasture hay production or alfalfa. The outlet facility
includes a collection system and pump base station (Project No. 3, page 9-65) to return
impounded water to Harvey Place Reservoir or the Diamond Ditch.
The temporary storage area is planned to slope less than 2% to accommodate irrigation
practices and have a common sump system to facilitate draining and water management within
the facility. The drain system provides the collection infrastructure needed to evacuate the
temporarily impounded water to Harvey Place Reservoir or the Diamond Ditch.
The five irrigation fields utilizing center pivot irrigation equipment range in size from 47 to 120
acres. These fields would not provide any temporary storage of water. Each center pivot
irrigation field is comprised of a central hub where the pivot assembly is connected to the
irrigation spans. The spans are composed of several segments of pipe joined together and
supported by trusses, mounted on wheeled towers with sprinklers positioned along its length.
The water source is connected to the central hub of the irrigation system thereby allowing the
spans to rotate around the pivot point. Different nozzles are available for the controlled release
of the water. Nozzle types vary from aerial spray, rotary sprinkler head to drip systems. Initially
freshwater will be used to irrigate the existing native grasses present on the Diamond Valley
Ranch. The center pivot equipment may ultimately use recycled water as its source for
irrigation depending upon the need for additional land to apply recycled water. This will require
securing a permit for use of recycled water on the Diamond Valley Ranch (Project No. 12, page
10-77).
South Tahoe Public Utility District
Recycled Water Facilities Master Plan - October 2009 Page 9-62