Centennial WSD 1996 WCPlan

• Project Type: Water Conservation Plan
• Project Name: Centennial Water & Sanitation District Water Conservation Plan
• Title: Water Management Study
• Date: 8/10/1995
• County: Arapahoe
• Water Conservation - Doc Type: Complete Plan

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Most of the water removed at Centennial's wellfield is considered replacement water
under the District's Augmentation Plan. This water is used primarily for the drinking water
supply. Increased runoff, exceeding historical levels to the South Platte River, also constitutes
replacement water. Thus, replacement water is either discharged from the Marcy Gulch
Wastewater Treatment Plant or from surface drainage gulches to the Platte River.

The Augmentation Plan allows the use of surface waters in a manner that does not affect
the priority system of water rights. Approved by the State of Colorado Water Court, the
Augmentation Plan's terms and conditions strictly control the District's ability to use its
replacement water. The plan is a complex document involving numerous safeguards to assure
that any removal of water in the South Platte does not cause injury to other water rights. The
State requires daily accounting to show no lowering of the water level below historical water
levels for the South Platte River. Since wastewater effluent fulfills replacement water
obligations, there may not be opportunity, at this time, for other reuse alternatives.

Groundwater Recharge

The District's Aquifer Storage Recovery (ASR) project is currently in the [mal stages of
evaluation. Results to date indicate that ASR is a viable technology for use at Highlands Ranch.
The District believes major [mancial, environmental and operational benefits are possible through
the use of ASR.

Aquifer Storage Recovery is the process of storing treated drinking water in a suitable
aquifer during times when surface water supply is available. The stored supply is recovered
from the same wells to meet seasonal-peak, emergency, or long-term demands. ASR is a water
management tool that offers the potential for increasing the storage capacity of municipal water
systems at low cost compared to conventional supply alternatives. ASR also offers the
opportunity to meet drought demand requirements without expanding surface storage facilities.

- n - -- . - u-whennCseasejhaf Vanation -rn -wateraemana-eXiStS; - convennorui!--facilities must -be
equipped to supply water to meet peak demands. This typically results in a system with excess
capacity available during low-demand months. With ASR, water produced in excess of demands
can be stored underground in a suitable aquifer and recovered during the high demand or
drought season to supplement the surface supply. A water supply system can thus be designed
and operated at a lower, more constant rate using ASR to meet peak seasonal and drought
demands.

Advantages of ASR over more conventional systems include:

· There is no evaporative loss..
· Water treatment facilities can be optimized.
· Useful life of existing aquifers can be extended.
· Capital costs for water storage and treatment are reduced.
· Facilities can be deferred or eliminated.

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