WSP11936

• File Number: 8276.500
• Description: Glenwood-Dotsero Springs Unit - Salinity Control Projects
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 1/1/1983
• Author: Golder Associates
• Title: Geology Working Paper for the Contour Ponds Site Near Mack, Colorado
• Water Supply Pro - Doc Type: Report/Study

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7.

DESIGN AND CONSTRUCTION CONSIDERATIONS

7.1 Layout of Evaporation Ponds

Figure 8 shows the Contour Ponds Site and three areas within that
site which are reasonably suitable for evaporation pond
construction. The site overall encompasses approximately 6,400
acres and the three site areas designated as the west area,
middle area, and east area, comprise approximately 1,160, 670,
and 1,510 acres respectively. The total available acreage of
suitable pond area at the Contour Ponds Site appears to be on the
order of 3,340 acres.

The selection of the three evaporation pond areas were based
primarily on topographic considerations. The areas were located
to avoid major north-south drainages. Additional area could be
obtained in the southwestern and northwestern parts of the site,
if necessary. This would require significant earthwork in the
south to flatten the very steep topography. The area in the
northwestern part of the site encroaches on the major drainage
through the middle and west areas and would require diversion of
a number of small tributaries. Therefore, the areas shown on
Figure 8 are those requiring the least efforts in terms of
earthwork construction and surface water diversion.

Of the areas selected the east and west areas have similar
geologic conditions with both having an average of approximately
18 feet of overburden soils which are underlain by weathered
Mancos shale. The surface topography at the west area is
slightly convex, while the east area is concave with McDonald
Creek marking the middle of the site. Since both areas form the
head water of drainages on the sites, diversion of surface waters
is only required around the perimeter of each area. The
evaporation ponds themselves would capture all of the direct
precipitation at these sites.

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The middle area is geologically different from the east and west
areas. A relatively thin veneer of soil, primarily residual
material from weathered Mancos shale, covers the site to a depth
of approximately 2 feet at all areas except along the western
edge near the major drainage where the thickness of alluvial-
colluvium materials increases to approximately 10 feet. These
surficial materials are all underlain by weathered Mancos shale.
The middle area is also topographically less smooth than the
other two sides and would require more grading to achieve a
uniform pond elevation.

The evaporation ponds would have to be constructed in a "rice
paddy" fashion with dikes following the general site contours.
The spacing of the dikes will vary depending on the steepness of
the sites and the height of each dike. However, extensive

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