Project Challenge:
For over 25 years, Klein and Hoffman (K&H) has provided
structural design and construction support services for major
additions and improvements to the Richmond Wastewater Treatment
Plant. The Effluent Treatment Facilities are located in the
flood plane with 100 year flood level at about 18 feet above
the grade. Construction of these facilities included a 100 ft
wide x 150 ft long x 70 ft deep reinforced concrete filter building
structure about 20 feet below and 50 feet above grade. Blower,
electrical and process control rooms were constructed over effluent,
influent conduits and wet well areas. This building was connected
to eighteen effluent filter tanks, a filter pipe gallery and
an access building, having an expansion joint between the two
structures. The structures were supported over steel H-Piles
and tie down rock anchors.
Project Solution:
The concrete mat foundations were supported over 50-ton steel
H-Piles bearing on rock, and were held by 50 ton capacity rock
anchors to resist uplift due to hydrostatic head of 40 feet.
During pile driving operations, it was discovered that some
of the piles were going out-of-plumb while others had bent.
Because of the varying rock elevations, pile tips were getting
damaged while going through the soil and then suddenly hitting
the hard rock. Protective shoes with cutting teeth were added
at all the piles tips to solve the problem.
During installation of the uplift rock anchors, in some areas,
the augercast holes (for No. 18 size threaded steel reinforcing
bars) kept caving in and were getting filled up with water and
debris. This was due to the highly weathered rock conditions
encountered in those areas. Large diameter casings were used
to keep the holes clean for grouting the annulat space between
the sheathing for the anchor and the casing. At areas, where
the top of the rock was just a few feet below the bottom of
the mat foundation, the steel piles could not be driven and
had to be replaced by specially designed concrete posts.
OWNER: City of Richmond Department of
Public Utilities
CLIENT: Greeley and Hansen, LLC
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