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Wastewater Collection and MBR Treatment Facilities
North Lake Recreational Sewer and Water District (NLRSWD)
Lake Cascade, Idaho
OVERVIEW
The NLRSWD was organized in 1994 to provide sewer service to approximately
1,600 recreational dwelling units/lots on the north end of Lake Cascade
near the City of Donnelly, Idaho. With Keller Associates acting as
the engineer, the initial $8 million sewer project - consisting of
115,000 feet of gravity pipelines, 58,000 feet of sewer pressure
lines, and 12 lift stations - was constructed. Since this initial
construction that served the northeast side of the lake, the District
has been expanded to include the entire northwest side of Lake Cascade
including the new Tamarack all-season resort as well as 16 other
major recreational developments around the north end of Lake Cascade.
The sewer system now includes over 100,000 feet of pressure lines,
over 200,000 feet of gravity collection and interceptor pipelines,
21 lift stations and a new membrane bioreactor wastewater treatment
facility with effluent disposal through land application and rapid
infiltration basins.
CHALLENGE
After completing an overall Lake Cascade facilities planning study,
District organization was the first and greatest challenge facing
Valley County and its consultant Keller Associates. Once the District
was organized, there came the challenge to develop a funding mechanism
whereby recreational land might be assessed for design and construction
of the initial sewer facilities. Once the initial facilities were
completed in 1999, the challenge became how additional funds would
be developed to facilitate continued growth and expansion of needed
sewer facilities. In addition to the funding issues, major design
and construction challenges were presented by the relatively flat
terrain and proximity to the lake. With no more than 20 to 30 feet
difference in elevation around the north end of Lake Cascade, gravity
collection systems to serve the residential dwelling units scattered
along the 15-mile north shore of the lake would be deep and in groundwater.
SOLUTION
Keller Associates implemented a county citizen’s advisory committee
with numerous neighborhood meetings, open houses, and mailers to
gain voter approval for the creation of the North Lake Recreational
Sewer and Water District. The initial funding problem was solved
by the development of what was at the time the largest local improvement
district (LID) in Idaho, to fund the initial $8 million construction
project. Eight additional local improvement districts have now been
implemented in order to design and construct sewer system expansions
into previously platted areas and Tamarack Resort. The first raw
land LID in Idaho was developed to provide the sewage collection
system for Tamarack Resort, a major regional Tamarack lift station,
seven miles of dual 10-inch pressure line, and a new bioreactor membrane
wastewater treatment plant. Additional funding of approximately $5
million was developed through developer prepayments - also unique
and a first in Idaho. The design and construction problems with the
flat grades throughout the area were overcome by the implementation
of a sewage pressure line network serving the entire north end of
the reservoir, with local gravity and pressurized collection systems
pumping directly into the sewage pressure line network. |
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