The project consisted of expanding the existing wastewater treatment
plant for the community of Maxwell in Colusa County, CA. Anderson
Dragline, Inc. worked as a grading subcontractor.
The primary grading feature was construction of a new 22 acre pond for
off-site storage of 181 acre-feet of treated water. Other features
included grading 70 acres of fields for use as biosolids application
areas, construction of a 0.5 acre tailwater pond, and raising existing
pond dikes to increase the capacity of the treatment plant. Raising of
the existing pond dikes at the treatment plant was staged to permit
continuous operation of the facility during construction.
A high groundwater table necessitated installation of an extensive
dewatering system and utilization of low ground-pressure equipment for
excavation and grading of the excavated area. Approximately 80,000
cubic yards of saturated clay soil was excavated, conditioned, and
placed in compacted embankments to create the new ponds. The clay soil
at interior pond floors was scarified, moisture conditioned and
compacted to provide low permeability. Interior pond slopes were
surfaced with riprap overlying geotextile fabric, and aggregate base
rock was placed on tops of pond berms as a drive surface.
12,000 lineal feet of conveyance and drainage ditches were excavated
around the perimeter of the biosolids application area. The entire area
was laser-graded to facilitate the designed drainage pattern.