October 2009 - South Tahoe Public Utility District

monitoring and SCADA control systems could be incurred if that level of sophistication is
desired.
9.6.2 Project Considerations
The pipeline alignment follows a portion of the Diamond Valley Road to avoid construction in the
steep existing waterfall portion of the Diamond Ditch.
An alarm system would notify District personnel of a flow problem in the Waterfall Pipeline and
shortly thereafter spillage would begin at the forebay. However a spill at this location would not
have critical consequences from a regulatory view but it may pose operational problems.
While the Diamond Ditch is the primary conveyance mechanism of the District‟s recycled water
system, the District must consider the issue of capital investment for improvements to the
Diamond Ditch that is owned by others.
9.7 Project No. 7 - District Pasture Subsurface Irrigation Pilot
Project
This project addresses the purpose and need statement:
PN-1. Inadequate land may be available to apply future recycled water flows.
The implementation of this project is contingent upon the need for additional lands to be
irrigated with recycled water that are subject to regulatory buffer constraints. It is a pilot project
to determine the worthiness of this relatively new irrigation concept.
The District owned land in the southwest corner of Diamond Valley is 200+ acres of pasture with
encroaching upland vegetation and is separated from Alpine County School District property on
the west by a 17-acre buffer zone; thus, this is an ideal location to pilot a subsurface irrigation
system (Figure 9.2, at the end of Section 9). This type of new technology is a sound way of
demonstrating the benefits of recycled water application while allowing for precise control of the
water budget and by eliminating surface water contact. These methods are being used in areas
with high public contact potential. The area used for the pilot subsurface irrigation system would
be very small; likely two to four acres.
9.7.1 Project Description
The subsurface irrigation system would require perforated plastic pipe to be installed
approximately 8 to 12 inches below the land surface on four on-acre sites. The design of the
subsurface pipe installation will depend upon slope, crop and soil conditions.
The conceptual cost of this system is $0.4 million. Annual maintenance is minimal; however,
replacement of the system is recommended every 3 to 5 years. This requirement makes it
attractive for pilot projects, research and education, but it is economically unfeasible in areas
that do not have recycled water human contact concerns.
9.7.2 Project Considerations
The end use of the land should be a primary consideration. Subsurface irrigation systems may
have a shorter functional lifespan in areas that are subject to livestock grazing. Lands that are
South Tahoe Public Utility District
Recycled Water Facilities Master Plan - October 2009 Page 9-71