WSP07452

• File Number: 8276.500
• Description: Glenwood-Dotsero Springs Unit - Salinity Control Projects
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 12/1/1985
• Title: Preliminary Assessment of the Salt Tolerant Emergent Plant ‎(STEP)‎ Process for the Beneficial Use and Disposal of Saline Water
• Water Supply Pro - Doc Type: Report/Study

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have the ability to grow and function at salinities
seawater, are able to over-winter or produce a full
seven months, and can tolerate extended periods of
Each also appears to have multiproduct potential,

These species
equivalent to
crop within
inundation.

Site Selection

Criteria were established to guide the selection of sites for process
implementation, The desirable characteristics of a site for STEP
operations were identified as open, level terrain, exposed to wind
and sun, located within the protective shield of the Grand Valley. A
prime determinant is soil composition, principally sands and silt,
with minimal clay and organics; this would be classified as marginal,
undesirable agricultural land.

Data Limitations

The available data are deficient in the quantitative definition of
upper salinity tolerance limits within emergent halophytes, including
the impact of high salinity on halophyte growth and
evapotranspiration rates, as well as product opportunities. These
effects must be known in order to engineer and cost the STEP process
facilities; this also applies to the development of operational
procedures and mana~ement strategies appropriate for the plants and
the process,

The criteria provided as guidelines to DEC during its development of
preliminary conceptual engineering designs of the STEP process were
the same as given in Table 1, except that evapotranspiration data
then available indicated rates at ,75 inches per day could reasonably
be expected, based on reports that may not have corrected for oasis
and large pond effects. Similarly, short-term salinity tolerance
levels were believed near 77,000 mg/l, based on inputs received from
professional consultations. While that level may remain achievable,
insufficient experience at this concentration is shown by the
available literature. IBR thus reduced its expectation to 40,000
mg(l, a value that is readily supportable, bnt after DEC had
completed its preliminary design and costing efforts, As a result,
the preliminary designs prepared by DEC are based on different
performance criteria. It is shown in Chapter Four that the impact
of this difference is not on the desi~n concept, but rather on area
requirements for pond facilities.

PRELIMINARY CONCEPTUAL ENGINEERING DESIGN

The STEP process flow sheet developed by DEC is shown as Figure 2.
This shows that 12,236 acre-feet of saline water is transported
annually via pipeline to spray evaporation cooling ponds. The
function of these ponds is to regulate the input water temperatgre so
as not to exceed the upper temperature threshold (taken us 86 F) of
the STEP crops: it is recognized that these ponds may not be needed,
Cooled saline waler is input to STEP crop production ponds where
water is consumed through evapotranspiration and feeds, chemicals,
and materials are prodnced, The output from the production ponds
passes into spray evaporation ponds for concentrating to saturated
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