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On May 14, 2009, Ecology issued an MDNS determination under
the State Environmental Policy Act (SEPA) for Phase 2 of the
Potholes Supplemental Feed Route project. After studying potential
impacts to the environment, Ecology determined that with appropriate
mitigation, there will be no probable significant adverse
environmental impacts.
Phase 2 MDNS
Phase 1 MDNS
Overview
In the late 1970s, the Bureau determined that a feed route to
Potholes Reservoir was necessary to ensure a reliable water supply
for the South Columbia Basin Irrigation District.
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The Columbia Basin Project (CBP) was designed to capture return flows
from irrigation on the northern half of the project for use in the
southern half of the project. However, irrigation in the north half
does not yet provide enough return flow to fully supply the south
half. To correct this problem, a feed route was developed to move water
from Banks Lake to Potholes Reservoir. The feed route transports
water through the Main Canal to the split, then south through the
East Low Canal (ELC) to Rocky Coulee Wasteway. The water is then
discharged into Upper Crab Creek near the north end of Moses Lake.
From this point, the water moves through Moses Lake and into
Potholes Reservoir at the Moses Lake outlet structure. Feeding is
done early and late in the irrigation season when demand for
irrigation water is low. At these times, the “unused” capacity in
the ELC is used to carry feed water to Potholes Reservoir.
This feed route solved the immediate problem in 1980 and is still
used today. However, the ability of this route to meet needs has
lessened over time. Improvements in irrigation efficiency in the
northern half of the project have led to even lower return flows and
an increased need for feed to supply the southern half. Demand has
also changed. Block 26 was added to the Potholes system in 1984 and
the East Columbia Basin Irrigation District (ECBID) Supplement No. 1
to the Master Water Service Contract allowed for additional use out
of the ELC. As a result, the demand on Potholes is greater, and the
amount of “unused” capacity in the ELC has declined. These factors
and a need for system reliability have led to the need for a
supplemental feed route (USBR, 2007 E.A.).
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Environmental Assessment
Since 2005, Ecology has partnered with the Bureau and invested $2.1
million to study the need for a supplemental feed route. In August
2007, the Bureau issued a final Environmental Assessment (EA) and
Finding of No Significant Impact for the Potholes Reservoir
Supplemental Feed Route.
Alternatives Considered
The draft EA evaluated four alternatives for conveying the waters: “No
Action,” Crab Creek Perennial (year-round use), Crab Creek Ephemeral
(intermittent use), and Frenchmen Hills. During the comment period,
the WDFW requested that, for purposes of fish and wildlife
management, a Crab Creek option be developed that, while primarily
used year round, included the option of occasionally providing only
spring flows. Operating the Crab Creek feed route intermittently
would be done to limit the spread of invasive species.
To accommodate
this request, the Crab Creek alternatives were combined using the flow
targets from the Crab Creek Perennial alternative: 500 cfs in the
spring and 100 cfs for the remainder of the year in those years when
flows are year round. Under this new alternative, less water can be
fed down Crab Creek in the years when it would be operated only in
the spring compared to the EA’s Crab Creek Ephemeral alternative
that had a spring flow target of 650 cfs. |
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To accommodate this shortfall in years when the Crab Creek route
would be operated in the spring only, the Frenchmen Hills route was
added to the combined Crab Creek alternative. With the Frenchmen
Hills route included, the new alternative could feed almost 80,000
ac-ft in years when Crab Creek is used only seasonally. Therefore, two
alternatives, the No Action alternative and the combined Crab Creek
and Frenchman Hills Wasteway alternative, were considered and
evaluated in the final EA.
The Bureau identified Crab Creek and Frenchman Hills Wasteway as
the preferred alternative. This alternative would release feed water
from Billy Clapp Reservoir through the four-by-four-foot outlet into
Brook Lake, a natural water body within the Crab Creek channel. Crab
Creek would then convey the water into Moses Lake and Potholes
Reservoir. Water would also be released from Billy Clapp Reservoir
via the Main Canal and West Canal, into the Frenchman Hills Wasteway,
and then into Potholes Reservoir (Bureau, 2007 EA). Implementation
of this preferred alternative is expected to occur in 2008.
More Information
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