HomeMy WebLinkAboutLetter from EngineerM.B.C.
Management
Office (936) 825-1603
November 12, 2009
Mr. Gary Fuqua
Fuqua Construction Co., Inc.
P.O. Box 1537
Navasota, TX 77868
CONSTRUCTION e MANAGEMENT• DESIGN
RE: Sheet Pile Retaining Wall
Hampton Inn & Suites
University & SH 6
College Station, Texas 77805
Dear Sir:
1015 Hwy 6 North
Navasota, TX 77868
Fax (936) 825-1624
MBC Management, a registered professional engineering firm in the State of Texas (No. F-789) performed
an inspection of the steel sheet pile retaining wall at the above location. The inspection was performed by
Paul E. Malek, P.E., a registered engineer in the State of Texas (No. 82860 with expiration date of June 30,
2010).
The inspection was requested due the movement of a section of wall near the north-east comer. The ·
retaining wall was constructed starting in March of 2005. The wall consist of interlocking steel PZ18 sheet
piles thirty feet (30') long with a poured in place concrete cap. The sheet piles were placed one foot (l ')
inside the property line. The piles were driven to a depth such that the top of piles were at an elevation of
between 261 .00 feet and 264.50 feet above MSL (mean sea level). The bottom of the creek along the north
and east side of the retaining wall was at an elevation of about 241.00 feet. Due to the varying side slope of
the creek, the piles were exposed on the creek side for a maximum distance of 12 feet. The PZ18 steel sheet
pile with 12 feet exposed, (12 foot of soil retained on one side) the bending moment on the pile would be
24,252 ft-lbs and have a safety factor (allowable load divided by actual load) of 5.76. Durning the inspection
the amount of exposed pile had increase, due to erosion of the creek side slope, 21.5 feet. At that amount of
exposure the bending moment is 124,148 ft-lbs and the safety factor is 1.12, this is below the generally
accepted maximum safety factor of 1.5.
We reviewed the plans submitted to the City of College Station for approval in March of 200 5. The plans
called for a PZ13 pile 30 feet long tied back to a concrete anchor 11 feet behind the face of the piles. There
were hand notations placed on the plans during a meeting with the City Engineering Department changing
the pile to a PZ 18 and deleting the tie-back anchor. The plans as noted were marked approved by the College
Station Engineering Department on March 23, 2009.
The retaining wall was constructed per the approved plans in the spring of 2005. At that time the maximum
height of exposed sheet pile was 12 feet. During the elapsed time the creek side slope has eroded to a point
that the maximum exposed face of the sheet pile is 21.5 feet. The piles have deflected in the direction of the
creek about four inches (4 in). MBC Management had made a recommendation to place rock rip-rap on the
creek side slope to prev~nt erosion. The College Station Engineering Department fi ll would not be allowed in
the flood way and did not approve the rip-rap. Now the entire side slope has eroded away in some areas,
additionally the bottom of the creek has been lowered due to high water flow rate.
In conclusion MBC Management recommends that 82.85 feet of the wall on the north side of the north-east
corner be anchored with steel rods spaced 4' -2" center to center. Additionally rock rip-rap be placed along
the bottom of the sheet piles such that no more than 19 feet of pil ing is exposed.
Ifl can be of further assistance to you, please contact me . ... _ .......... ,,,,
Respectfully, ...:""'°;~\'... •• ~ ~ .. ; ~-t: ''"
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Structural Engineer ~~\ 82860 .:!/f J fto;• • .<1c 5<;:.Q.···;$'~ Paul E. Malek, PE ,,~s;"··~N .. ···~0; \\ IONAL '€:. __
MBC Management ,,,,,~ .... -