Even though it has just started, and on a modest scale, an ambitious, proactive street paving improvement program already is showing results for Trenton, NJ.
Most of Trenton’s streets and roads are not in desperate shape — yet. But, then, most of them were built years ago and could benefit from a program that stresses continual renewal instead of emergency repairs.
However, similar to a number of small cities and municipalities in the state, “Trenton has had to contract out basic resurfacing work,” said Mayor Douglas M. Palmer. “In recent months, however, we have trained our staff to use ’milling and overlay’ equipment, which enables us to respond to basic and preventive resurfacing needs.”
For its equipment, Trenton selected a package from Wirtgen Americas through dealer CC&T, Folcroft, PA: a Wirtgen W1900 cold pavement milling machine, a Vogele America Pro-Pav 880 RTB tracked asphalt paver, and a Hamm HD 90 double-drum roller/compactor. In addition to supplying the equipment and servicing it, CC&T provided training and guidance to Trenton street crews on the state-of-the-art equipment.
According to the city, the equipment package cost more than half a million dollars, but Trenton Public Works Director Eric Jackson expects the city will initially recoup this amount and then realize further savings by not having to contract out work. The city first used the equipment on a 39,240-sq.-ft. (3,645 sq m) pilot project on a small connecting street; the job cost less than $20,000, compared with contractor estimates exceeding $100,000. “We expect similar savings on each job,” said Jackson.
For its first major in-house resurfacing and paving project, more than 100,000 sq. ft. (9,290 sq m), Trenton selected several streets in Hiltonia, an upscale single-family-residence neighborhood, for two reasons: One, it is not heavily trafficked and there is plenty of right-of-way space on the sides of the streets. In the more urban areas of Trenton, side-by-side duplexes or row houses crowd the streets and there is more foot and auto traffic and more need for on-street parking by residents. Two, this area had previously undergone underground utility work and extensive curb-and-gutter replacement (by outside contractors), so there was definitely a need for finish paving.
According to Wale W. Onitiri, street superintendent of Trenton, the neighborhood presented an unusual challenge. This area was built up some 50 to 60 years ago, and on some streets the base course is not an asphaltic mix but crushed stone, approximately plus 1.5 in., minus 3.5 in. (3.8 and 8.9 cm) in size, which had been put in place, rolled out, compacted and oiled, then topped with a single thin wearing course. It took a deft touch by head equipment operator Jim Page to disturb as little as possible of the base course while removing all the old 2-in. (5.1 cm) overlay pavement with the Wirtgen unit. Then the paver put down a 1.5 in. base course over the crushed rock, followed by the wearing surface overlay.
Originally, Onitiri and his crew planned to do the Hiltonia section soon after the city purchased the equipment, in late fall 2002. If the previous winter had been any indication, they would have had plenty of time.
However, the opposite happened: there were early heavy fall rains and cold, nasty weather, followed by one of the longest, most severe winters in recent history. With heavy snowfalls at least once a month, crews were working overtime with plowing and emergency road repair tasks.
It wasn’t until April that crews had a clear shot at the entire project. And, as Onitiri pointed out, “We also changed our approach. We’re milling all the streets first, then paving. Before we would have done it in pieces, mill and pave, mill and pave. So we needed a consistent stretch of good weather.”
The Hiltonia project actually was a good test case for his crew, noted Onitiri. “The majority of the streets of Trenton have a better base than this, not loose rocks. This area is an exception.”
Onitiri said the next projects scheduled include a main traffic artery in the city; a major thoroughfare in a residential neighborhood, and a large (114,000 sq. ft. [10,590 sq m]) job on another main street. “In all we have at least 25 miles of roads and streets that need work. There hasn’t been a coordinated street resurfacing here in a long time and a lot of streets show it.” And few of these are wide, straight, uninterrupted stretches; instead they’re two lanes with parking on one or both sides, numerous bends and frequent major intersections with stoplights. So, hopefully, it will be a long time before Onitiri and his crew have to think about going back to the same street twice.
City of Trenton’s Equipment Package Incorporates Latest Technology
The Wirtgen W1900 cold milling machine has a cutting width of up to 6.5 ft. (2 m), but the operator has the option to switch cutter drums to other widths. Maximum depth is 12 in. (30.5 cm), so the machine also can be used for finish grading and even shallow trenching. The unit weighs 54,850 lbs. (24,880 kg) and is powered by a 435 hp (325 kW) diesel; estimated productivity is more than 300 tons (270 t) per hour.
The Wirtgen’s operation is continuous and the output is crushed asphalt, which can be reused as subbase or permitted fill. This is in sharp contrast to the traditional method of pavement removal, as Jim Page pointed out. “Previously we would attach a large ripper tooth to a motor grader, where the blade usually goes, and rip and pry up chunks of pavement,” he said.
Crews then would sometimes separate these by hand and load in trucks, or, more often, use a wheel loader with a toothed bucket. This was a time-consuming process sometimes involving heavy lifting, and the waste product was bulky and not good for much of anything except a poor fill.
The Vogele model 880 RTB tracked paver has a standard 8-ft. (2.4 m) width. It is powered by a Cummins 152-hp (113 kW) diesel engine driving two hydraulic motors with two speed ranges; top speed is 8.5 mph (14 kmh).
Hopper capacity is 190 cu. ft. (5.3 cu m). Overall length is 17 ft. (5.1 m), width 8.5 ft (2.5 m), and height 9 ft. 8 in. (3 m), so the unit can easily be roaded with standard lowboy trailers. Screed widths are available from 8 to 15 ft. (8 to 16 ft., optional).
The Hamm model HD 90 is a 66-in. wide (1.7 m), double-drum articulated vibratory compactor weighing 20,100 lbs. (9,120 kg) and delivering 17,100 lb./drum (7,760 kg) centrifugal force. It has an infinitely variable hydrostatic drive with a top speed of 9.4 mph (15 kmh). The 3.5 in. (8.9 cm) offset to either the right or left side of the articulation joint allows increased rolling width and pavement joint “pinching.” Operations with single or double-drum or no vibration are available.