October 2009 - South Tahoe Public Utility District

In the future, the District could possibly implement an injection well program for it‟s recycled
water. Implementation would depend on various factors including insufficient sites for land
application of the recycled water, the quality of the treated wastewater discharged by the
District‟s treatment facility, and cost/benefit considerations. The benefit of an injection well
program for the District is primarily another method of managing its recycled water. An injection
well program would also have an environmental benefit of recharging groundwater.
The Diamond Valley Ranch is a good candidate for injection well sites. A pipeline extending
from the existing C-Line would be needed to convey water to injection well site(s). The quality of
the recycled water would need to be improved to implement an injection well program and the
program would have to be permitted by the Lahontan Regional Water Quality Control Board.
Groundwater transmission studies would be necessary to evaluate, design and estimate the
effectiveness of the injection well program.
An injection well program would be developed only if sufficient land is unavailable for irrigation
with recycled water. Disadvantages include the significant capital expenditure required to
implement the program (including treatment plant improvements and injection well construction)
and the project generates no revenue for the District.
13.6 Decision Tree and Causal/Direct Effects
Figure 13.1, Contingent Project Decision Tree, lists projects whose implementation is contingent
upon application of a trigger or completion of another project. Project 1, Irrigate Diamond Valley
Ranch with recycled water, is a recommended project and is included for continuity. Several
future projects are also included to provide additional project options. Future master plan
projects shown are: Project 7 (District Pasture Subsurface Irrigation Pilot Project), Injection
Wells and Extend the C-Line to Nevada. The Decision Tree lists both recycled water and fresh
water triggers. A trigger is described as a change of current conditions. The Decision Tree
shows projects arranged in four tiers. Tier 1 projects are considered more likely for initial
installation than the remaining tiered projects as they can be easily implemented and will
provide needed system improvements.
Selection of any project from the Decision Tree for implementation should not be based solely
upon the Decision Tree but upon all current information known by the District which may impact
their operations.
Tier 1 contingent projects include: Project 14, Snowshoe Thompson No. 1 conveyance capacity
improvements and Project 17, Diversion Ditch for Stormwater Flow away from Harvey Place
Reservoir and to Indian Creek Reservoir. Project 14 is a freshwater project which could be
implemented when impacted by any of the following three triggers: 1) Capacity and reliability of
the freshwater conveyance system is compromised, 2) water surface elevation in Indian Creek
Reservoir is not being met consistently and 3) Hypolimnetic Oxygenation System does not
improve Indian Creek Reservoir water quality. Project 17 is identified as a recycled water project
and could be implemented by the trigger involving Harvey Place Reservoir storage capacity
concerns.
Tier 2 projects include Project 8 (West Fork Pipeline) which could utilize the upper
Fredericksburg roadway alignment to distribute recycled water to lands west of the West Fork of
the Carson River. This project would probably be implemented if irrigation of Diamond Valley
Ranch with recycled water was already maximized. Another Tier 2 project is Project 10 (Wade
Valley Pipeline), from Diamond Valley to the waterfall pipeline forebay and installation of a
South Tahoe Public Utility District
Recycled Water Facilities Master Plan - October 2009 Page 13-98