WSP12636

• File Number: 8282.300
• Description: Colorado River Operations and Accounting - Lower Basin Administrative Procedures
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 8/1/1996
• Author: DOI-BOR
• Title: Description and Assessment of Operations-Maintenance and Sensitive Species of the Lower Colorado River - Volume II - Appendices-Etc - 08-01-96
• Water Supply Pro - Doc Type: Report/Study

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maintenance by hauling and placing the riprap on the banklines and levees. Reclamation
endeavors to locate the quarry sites within economical haul distances from the stockpile sites.

With the exception of bankline work in the Yuma and Limitrophe Divisions, most needed
levees and banldines along the lower Colorado River are in place, and future work will not
require the construction of new structures. Future work will only include periodic structure
repair and stockpile replenishment as required to compensate for material that has been used
for routine maintenance requirements and to repair flood damage. The annual amount of
material needed may vary. The anticipated annual average need is 80,000 cubic yards of
mined material through the year 2005.

Material used for routine maintenance activities and to repair flood damaged structures can
be obtained from approximately 45 existing material stockpile sites. These sites are located
along the 10wer river from near Davis Dam to the SIB. Material from any of these
stockpiles may be used to repair flood damaged structures. The anticipated 80,000 cubic
yards of material needed to annually replenish these stockpiles may be obtained from any of
the existing quarries as shown on Figure C-l.

The first dredging on the Colorado River system occurred in the Yuma area in the early
1900s, and during the following 40 years incidental channel improvements were effected to
correct local problem areas. Dredging is by definition the excavation of material under
water, and the first machines were essentially of the dragline or bucket type.

The Bureau of Reclamation acquired the 16" hydraulic suction dredge "Colorado" in 1949.
Work began in the Mohave Valley area to alleviate the flooding problem at Needles and was
extended upstream to stabilize the meandering channel alignment. Subsequently, the dredge
"Colorado" was moved to the Blythe area in the southern Palo Verde valley where it
accomplished the channel realignment known as the Cibola Cut. The "Colorado" was then
dismantled and replaced with 12" hydraulic suction dredges which are better sized for the
scope and nature of the maintenance dredging and the remaining improvement projects.

The present and foreseeable dredging program is described later in the sections pertinent to
specific river divisions.

The Colorado River system has approximately 50 backwaters that would benefit from
dredging and other physical renovation. The Back Water Subcommittee of the Lower
Colorado River Coordinating Committee is presently prioritizing a list. Reclamation is
prepared to provide dredging to those backwaters on a cost-shared basis.

Major Activities Along the Lower Colorado River

For administrative purposes the lower Colorado River has been divided into maintenance
divisions which are roughly determined by different physical characteristics, which are shown
in Figure 2. The following discussions are indexed according to those divisions.

Appendix C - 3