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Warren County Parking Lot Paving 2021

The public lot serving the Warren County Old Courthouse and Old Administration Building in Lebanon is resurfaced under this project: failed areas cut out and patched five inches deep, the edges milled so the new surface meets the entrances flush, and about 5,500 square yards of new ODOT-specified asphalt striped back to the original layout. Prodigy supplies the materials, crews and equipment, and schedules the work with county staff so the lot comes back in usable pieces and the courthouse keeps operating. It is written against a pre-bid TIPS cooperative contract.

The lot serving the Warren County Old Courthouse and the Old Administration Building in Lebanon is a public lot in the working sense of the word. Jurors, people with hearings, and county staff use it on a weekday schedule that does not pause for a contractor, and the pavement had reached the point where patching was no longer the answer.

The proposal on file is a straightforward resurfacing of that lot. Roughly 250 square yards where the pavement had gone through are removed and pre-patched to a depth of five inches. About 900 square yards are transitionally milled and hauled off site, so the new surface meets the existing grades at the entrances and along the edges rather than standing proud of them. The lot then takes a tack coat throughout, a half-inch leveling course, and an inch and a half of surface course across approximately 5,500 square yards, and is striped back to its original layout. The materials are ODOT-specified throughout — Type 2 intermediate course, 407 tack, Type 1 surface course.

Prodigy supplies the materials, the labor and the equipment for it: milling machine, saw, mechanized sweeper, hot box, paver, ten-ton vibratory roller, striper. The schedule is worked out with county staff so the lot comes back in usable pieces and the courthouse keeps functioning while the work goes on. The proposal is written against a pre-bid TIPS cooperative contract.

Newly paved asphalt drive and curb at the Warren County lot

New asphalt roadway running between mature trees on the Warren County property

Edge of the new Warren County asphalt against fresh concrete curb and gutter

Technical Discussion

Transition milling: adding two inches without burying the curbs

The lot serving the Old Courthouse and the Old Administration Building received a two-inch overlay across about 5,500 square yards: a half-inch leveling course and an inch and a half of surface course. An overlay is the economical way to renew pavement whose structure is sound, because it keeps every inch of the old asphalt working as base. It also raises the entire lot by two inches, and a parking lot is surrounded by things that cannot rise with it.

Two sections at a curb. A 2-inch overlay with no transition leaves only 4 inches of curb showing. With the old surface milled on a taper toward the curb first, the overlay finishes flush and the full 6 inches of curb remain. — Figure 1 — Transitional milling lets a lot gain 2 inches in the middle and none at the edges.

Where two more inches do not fit

A standard curb shows about 6 inches of face. Pave two inches against it and a third of the curb is gone, along with a third of the gutter's capacity to carry water. Catch basin grates end up in a two-inch hole. Sidewalk ramps and building entrances meet the pavement at a fixed elevation, and the accessibility standards allow a change in level of no more than half an inch, beveled, along a route. Where the lot meets the street, a two-inch lip is a hazard for every car that crosses it.

Milling only the edges

Transitional milling solves this. Along curbs, around drainage structures, at walks and at the street tie-ins, the old surface is milled on a taper, zero at the inboard end and the full two inches at the edge, so the new asphalt finishes flush with what it meets. The middle of the lot, where nothing constrains the grade, is left at full thickness and simply overlaid. On this project about 900 square yards were milled, roughly a sixth of the lot. Milling all 5,500 square yards would have removed two inches of sound pavement everywhere in order to put two inches back, which costs more and leaves the lot no stronger than before.

Patch first, then level

Before any of that, about 250 square yards of failed pavement were cut out and patched to a depth of 5 inches. An overlay bridges small cracks, but it cannot bridge a failed base, and an area that is pumping or alligatored will break through new asphalt within a few seasons. The half-inch leveling course then took out ruts and low spots, so the surface course went down at a uniform inch and a half and compacted evenly.

On an overlay proposal, look for three quantities: the patching, the transitional milling and the overlay itself. If only the third is listed, ask what happens at the curbs, the drains and the doors.

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