Audit of Major Commercial & Irrigation Water Accounts

• Project Type: General OWC
• Applicant: Town of Castle Rock
• Project Name: Commercial & Irrigation Water Audit
• Title: Audit of Major Commerical and Irrigation Water Accounts
• Date: 6/29/2006
• County: Douglas
• Water Conservation - Doc Type: Final Report

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Audits of Major Commercial and Irrigation Water Accounts
Town of Castle Rock

Landscape Improvements
Estimating the cost benefit of more water efficient landscapes was another key
component to this project. Landscape improvements were categorized as replacement of
bluegrass or other high water use plant material with a mix of hardscape and xeriscape.
Hardscape includes the removal of the existing bluegrass and other unwanted, non-
functional plantings as well as capping off the existing sprinkler heads. The landscape is
then covered with geotextiles over which rock landscaping is placed. This type of
landscaping requires no watering, and limited maintenance.

Xeriscaping, which can include a wide range of plantings, requires the removal of the
existing bluegrass or other high water use plant materials, and in many cases, the
replacement of the existing irrigation system. The soil that remains after removal of the
high water use plant materials is amended with sand for drainage and organic material to
help breakdown the clays that are prevalent throughout the Castle Rock area. Once the
soil is appropriately amended, subsurface drip irrigation and limited surface spray
irrigation is installed in those areas where planting materials will be placed. For the
purposes of this study, it has been assumed that the planting will include a mixture of
native grasses, to maintain green spaces, as well as a mixture of low water use native
grasses, trees, shrubs, and flowers. Xeriscape plant materials are expected to reduce the
water use from bluegrass by 60 percent, which is about 32 percent of ET (Bureau of
Reclamation, 2004).

It is expected that in practice, all entities will choose to implement their own combination
of hardscape and xeriscape to meet future landscaping needs in accordance with the
Town ordinances. In most cases, due to soils or economics, or both, it is expected that
the majority of the landscaping will become hardscape, or in larger setting, allowed to
revert back to native, with smaller, more accessible areas becoming xeriscaped. This
report provides the cost and benefit for both hardscape and xeriscape in an attempt to
develop a likely range of costs for the proposed landscape improvements. Individual
facilities will be left to choose the degree to which they implement some combination of
hardscape, xeriscape and natural areas.

The cost ofhardscape and xeriscape can vary widely depending on the size of the retrofit,
the nature of the underlying soil, the type of rock or planting material used, the type and
extent of the irrigation system installed, etc. Based on the Y ARDX Report (Bureau of
Reclamation, 2004), which looked at over 200 projects in the Front Range, the cost of
xeriscape retrofits range from $ 0.90 to 1.45 per square foot. As another price point, the
Target Store in Castle Rock just completed a retrofit of approximately 2 acres of
landscaping, which included removing bluegrass, replacing it with native grasses after
amending the soil, and planting limited amounts of flowers and shrubs at a cost of
$70,000, or about $ 0.80 per square foot. Although the retrofits could cost into the higher
range as estimated by the Town, for purposes of this report and analyses, hardscape was
estimated to cost about $ 0.60 per square foot, and xeriscape was estimated to cost about
$ 0.80 per square foot given that the typical retrofit will occur in a space of one half acre
or larger which allows for some economy of scale.

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