By: Jan R. Prusinski, PE
The City of Garland (pop. 228,000), delivers concrete streets to its residents in an unconventional way that saves money, time, and improves response to its residents and businesses. Steve Oliver, PE, Garland's Director of Streets, presented Garland's unique street construction approach at the American Concrete Institute's recent Dallas Spring Meeting. His presentation was made during the "Symposium on Integrated Cement-Based Pavement Systems" held on March 19th at the convention.
Garland's approach is to use its own Street Department personnel and equipment to construct concrete streets from the subbase to the surface--essentially an internal vertically-integrated concrete street construction operation. Most cities have street departments that can do some street maintenance (concrete or asphalt), and some even have asphalt pavers to build a limited number of flexible pavements. However, Garland has chosen to construct its own concrete streets internally. This is unique for a city to take on these tasks directly, and not contract them out.
The main reasons for this approach are time, money and flexibility. Garland is the 12th largest city in Texas and has 698 centerline miles (2,328 lane miles) of streets, 81% of them concrete. Tax note refinancing in 2006-7 allowed the City to consider purchasing the equipment necessary to construct its own streets. As a result, Garland purchased a slip form concrete paving machine, a pug mill, and a concrete crushing machine.
Now the city uses the concrete recycling facility (with the crusher) to cost-effectively produce recycled concrete aggregate for cement-treated base (the crusher is currently operated by a vendor under a 10-year lease agreement). The crushed aggregate is taken to a City-operated pug mill, where cement and water are mixed with it, and the CTB is transported to concrete street or alley projects. Concrete streets are paved using a Gomaco slip form paver operated by City personnel, and alleys are paved using a paving screed (concrete is supplied by local ready-mixed concrete producers).
One interesting note is that the city's concrete recycling center actually makes a royalty from the concrete crusher lease, thus providing revenue enhancement for its residents. Additionally, the concrete crushing, and the city's use of recycled concrete for the CTB is a green construction technique, that saves the use of virgin aggregates (that must be trucked from remote locations).
Garland has found that with its large inventory of concrete streets, and its commitment to provide long-lasting, low-maintenance concrete pavements to its residents, the purchase of the equipment and use of Street Department personnel provides a cost savings compared to outside contracting, because of the consistent base load of work.
Oliver summarized the 2010-2013 fiscal year construction projects, which include 43 street reconstruction projects (23 lane miles) and 19 alley reconstruction projects (3.4 lane miles). A typical concrete street uses a cement/lime stabilized subgrade, 6 inches of cement-treated crushed concrete subbase, and a 6 or 8 inch concrete surface.
With the internal concrete street construction approach used by Garland, it has been able to maintain an average pavement condition index of 92 for all streets, well above the 70 target minimum. City taxpayers realize a cost savings versus traditional external contracting, and city forces are more flexible and time efficient in addressing residents' and businesses' needs, as they are not slowed down by contracting/procurement, nor constrained by contractual arrangements.
Other cities with a high base load of concrete construction should look at the model paved by Garland, and determine if that is an efficient way to deliver concrete streets to their citizens and businesses.
"This blog was previously posted in the Cement Council of Texas' "Texas Cement and Concrete Blog" (now inactive) and was carried forward to the current blog ("Cementx Pavement Blog") as it contains content that may be of interest to the reader".
The Cementx Pavement Blog seeks to make pavement owners, engineers and contractors smarter about selecting, designing, constructing and maintaining pavements. New blog postings began February 1, 2017; however, we carried over pavement-related blog postings from our older blog, the "Texas Cement and Concrete Blog," which ran until December 2016.