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MIAMI ENGINEERING SERVICES, LLC Jack L. Dalrymple, P.E.
P.O Box 554North Miami, OK74358 Ph. 918-533-6889 Fax 918-540-0067 OK Lic # 20645
MO Lic # 2003006445
20 Dec 2013
Mayor and Council
300 Commerce Avenue
Commerce, Oklahoma 74339
RE: Wall Structure Commerce, Oklahoma (Maple, Walnut, 4th & 5th Streets)
Dear Mayor and Council,
Following is a report regarding structural condition of the rock wall. Known as the “Old Football Field”, “Seymour Field” and the “Practice Field”, this wall structure has been a landmark for decades. The purpose of this investigation is to determine if this structure presents a collapse hazard. We will also offer a preliminary review of possible alternate solutions of repair/replacement.
Please reference attached drawing (A1). This drawing can be used for relative location and examination of wall sections remaining.
As Built
As built the four walls of the structure identify a large area defined inside Walnut on the East, 4th Street on the South, 5th Street on the North and Maple on the West. This structure uses a complete city block.
There is an entrance to the “Old Football Field” at the corners of Walnut and 4th. Photo (B1). There is an 8 foot walk gate center on Maple Street. Photo (B2). This entrance separates the concrete bleachers. On 5th and Maple is another entrance. Today much of the 5th street wall is missing Please see Photograph (B3).
Much of the North wall has been removed. This report will be limited to the remaining wall sections. The wall was removed by city forces in 1987 when the wall began to lean drastically to the North. At that time the concern was that removal would prevent sudden collapse and possible child endangerment.
Wall Design
The average height above grade is 7.5 feet. In general the wall height above the footing is 8.0 feet. The wall is tapered from base to top at a rate of 2 Feet wide at the bottom to one foot wide at the top. There are columns throughout the wall that have a typical width of 2 feet by 3 feet at the bottom which also tapers to the top. Column spacing is consistent except for beginning and terminating members as geometry of the lot allows. Typically that spacing is 16 feet between columns.
Footing Design
Wall footing is poured in place concrete 1 foot thick. It has a varying width of 2 to 3 feet. No Tension reinforcing in the footing has been observed at the excavation sites.
Wall Failure modes defined
Phase one failure is a developed structural crack from top of wall to bottom of wall. This crack extends through the wall creating a distinct discontinuity having no tension reinforcing members attached to any other section. This type of failure creates an independent stand-alone structural failure that when left unrepaired progresses to phase two.
Phase two failure is the above with the added longitudinal displacement enlarging the crack through weathering and frost heaving mechanisms. Often phase two is characterized by parts of the now independent stand-alone section beginning to break off. Left unrepaired this phase develops into phase three.
Phase three failure is the above with the added transverse displacement of the wall section. Typically this section will be unrepairable without complete dismantling and rebuilding.
Phase four is collapse.
Wall failure modes identified
An examination of the wall identifies a phase one failure throughout the existing structure every 20 to 25 feet without exception. Please see Photograph (B4). Systemic footing failure being the underlying cause. Without intervention, the wall sections that rest on the failed footing are destined to continue through the above defined failure modes to the collapse condition. Please see Photograph (B5).
Phase two and three failure modes are common throughout the entire structure. Please see examples in photographs (B6) and (B7).
Some support columns are in phase two. The gate column on the corner of Walnut and 4th has an attached steel gate. This column is in advanced stages, Phase 3, to the degree that it is hard to tell if the gate is supporting the column or the column is supporting the gate. It may be prudent to remove the gate from the column as soon as possible to prevent a more rapid progression. Please see Photograph (B1).
Repair or Removal
All visible cracks can be filled with mortar. This type of repair will definitely improve the aesthetics but will not improve the structural condition of the wall. Without structural modification the wall would continue through the above failure progression.
A structural repair would address the base failure. Base failure has been identified as the footing. Please see Photograph (B5). A standard footing design would include a reinforced cross section matrix of more than three times the mass of what is in place. The cost of retrofitting a footing design to accommodate the current wall would be more than two times the cost of complete removal and replacement. Adding to/reinforcing existing requires penning and sophisticated placement. This activity drives costs and time on task over the top.
Alternatives
There are many alternatives. Please use the following as a base line for just a few of the possible solutions.
Alternative 1. (Do Nothing)
Let the wall come down on its own in sections with time and gravity. The wall will fail a piece at a time after Phase three is exceeded. City crews would then clean up the debris, level the ground and wait for the next section to fail.
Alternative 2. (Remove sections that exhibit phase three and above, continue to monitor)
City crews could remove any section of wall that exhibits phase three failure before that section progressed into collapse.
This alternative would require monitoring after every weather event that included rain, ice, snow wind or freezing. The monitoring would be to determine if there had been changes to the wall. If a section of wall progressed to phase threethen city workers could safely remove that section before collapse.
Alternative 3. (Remove wall without replacement)
City crews are capable of total removal. A site for the debris will have to be found. Fill and sod will be required.
Alternative 4.
Remove wall with replacement. Hire a contractor to remove the wall saving and cleaning the rocks. Replace with a designed footing and columns. The reinforced design will include a wall section of concrete between each pair of columns. The wall section can then be veneered with rock saved and cleaned from the old wall.
This wall will have historic significance with the old rock replaced. Please see preliminary conceptual designs attached as Drawings (A2). A cost for this design is also preliminary. Within a reasonable range this build will cost about $405,000.00.
A word of caution regarding the old rock; it is very possible that the rock will contain lead. It is very possible that the footprint of the wall will have lead contaminated soil. A careful look at the rock and the soil is warranted.
Respectfully Submitted,
Jack L. Dalrymple, P.E.