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Water
Master Plan
HARVEST
WELL PRODUCTION TO AUGMENT DEEP AQUIFER SUPPLY
As
part of the upcoming wastewater project, the District will be installing
harvest wells to manage the upper aquifer and potential localized
mounding of groundwater in the areas of the community leach field
systems. This harvest well water will be used, in part, to augment the
deep aquifer water supply for potable water purposes. This upper aquifer
harvest well water may also be used directly for irrigation in
conjunction with the proposed recycled water system (see Chapter 6). The
upper aquifer harvest well water must be blended with the deep aquifer
supply to meet water quality standards for nitrates. Basin-wide, it is
anticipated that 650,000 gpd of upper aquifer water must be harvested to
manage the upper aquifer and control the potential mounding effects of
the future wastewater effluent disposal system.
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SUPPLEMENTAL
WATER SUPPLY WELLS
With
the Palisades Well supplying nearly 50 percent of the total LOCSD water
supply, consideration must be given to the ability of the remaining
wells to supply maximum day demand in the event that the Palisades Well
is out of service. Should
this be the case, the District will not be able to meet build-out
maximum day demand of 1,869 gpm. The
Palisades Well alone can provide 750 gpm (maximum sustained flow during
peak month), while the other wells collectively produce 830 gpm.
In addition, this same deficiency exists today, should the other
system wells need to meet current maximum day demand of 1,585 gpm.
Based on this analysis, it is recommended to construct two new
production wells that will provide a total of 1,000 gpm to ensure that
maximum day demand can be met in the event that the Palisades Well is
out of service. The
recommendation allows for variance in blending ratios of the harvest
wells with the new production wells.
It is recommended that the new deep wells be located adjacent to
proposed harvest wells for bending efficiency.
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RECYCLED
WATER STUDY
In
order to augment the projected 60 AFY water supply deficit for the Los
Osos Groundwater basin, a recycled water study was conducted to identify
the potential for recycled water use from the future wastewater
treatment plant. The study
focused on six sites within the community, including Sea Pines Golf
Course, the four schools (Monarch Grove Elementary, Los Osos Middle
School, Sunnyside Elementary, Baywood Elementary), and the Community
Park.
These
six sites collectively include approximately 35 acres of turf, plus 4
acres of ornamentals, that can be irrigated with recycled water.
Although the future quality of the treatment plant effluent is
not known, it was reasonably projected based on the known potable water
quality parameters. The
District’s well water supply is of excellent mineral quality, and thus
treatment plant effluent is expected to be of good to excellent quality
from an agronomic standpoint. A wastewater supply and demand analysis
was performed, and it is anticipated that any required diurnal storage
for the recycled water peak demands can be met through the planned
treatment plant effluent storage at the Tri-W site.
The
study projects that 115 AFY of recycled water can be used for irrigation
at these six sites, to augment the potable water supply.
In-lieu groundwater pumping of the upper aquifer was considered;
however, the required additional distribution system, wells and storage
facilities associated with this option are undesirable from an economic
standpoint.
The
sensitivity of selling recycled water to San Luis Coastal Unified School
District (SLCUSD) within the Cal-Cities water service area was
considered. Based on
meetings with Cal-Cities, the Cal-Cities Water Company is supportive of
water conservation measures, but is concerned about the loss of water
revenues from water sales to SLCUSD.
Sale of recycled water to SLCUSD, and corresponding loss of
potable water revenues, could
impact Cal-Cities rate payers by approximately 3 percent.
Recycled water sales to Sea Pines Golf Course and San Luis Obispo
County (Community Park) will not impact water rates, as both users
currently use private well water for irrigation.
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WATER
DISTRIBUTION
The
District’s water distribution system includes over 25 miles of water
distribution pipelines, three water storage tanks, five water supply
wells, one main gravity zone, and one hydro-pneumatic zone equipped with
a booster station. A
detailed hydraulic water model was developed using WaterCAD for the
LOCSD water system. The
model was calibrated through field hydrant testing to accurately
represent existing hydraulic characteristics.
Once the model was calibrated accurately, model runs were
simulated to assess system performance.
In
the analysis of the existing LOCSD distribution system, some areas in
the network were found to experience less than desirable pressures
during domestic demands and substandard pressures and/or flows under
fire flow conditions. The
distribution system also has an inadequate “backbone” or a series of
larger diameter, looped pipes allowing flow to travel to several
sections of the system with little head loss. The various improvements
needed to improve water circulation, service pressures, and to meet fire
flow demands, are discussed in Chapter 7.
In
addition to water system hydraulics, there are other considerations to
enhance and improve the LOCSD water system. Such considerations include
replacement of polybutylene water services (which have not held up well
in the past), upgrading the water meters, pump station upgrades, water
storage, and seismic considerations in the event of a significant
earthquake event. These
improvements are also summarized in Chapter 7.
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