A reader recently wrote to us asking about why Wellesley seemed to be increasingly paving roads — Beechwood and Overbrook among them — with a gravel-like substance instead of smooth blacktop. “It’s not great to drive on or bike on. When driving, little rocks kick up at your car and on a bike, the ride is very bumpy… Any idea why they chose to finish the roads with this method instead of traditional pavement?”
I caught up with Beth Gildae, assistant superintendent for the town’s highway division, via email to get an answer. Acknowledging that this so-called “chip seal” approach to paving is a “very sensitive topic,” she shared both a short-and-sweet and a more thorough explanation of how the town approaches street paving.
First, the brief explanation: “These roads received a rubber chip seal treatment after they were prepared with a leveling course of asphalt to re-establish the crown of the roadway and provide a smoother ride. This treatment is one of several used as a part of the Capital Street Resurfacing Program [which is in place to maintain safe travel on more than 112 miles of public roadway].”
And now for the more elaborate explanation, which I’ve edited down:
“Wellesley uses several resurfacing strategies and techniques to extend pavement life and provide a good driving surface. The appropriate resurfacing treatment for a roadway depends on the existing pavement condition and many other factors. The Town evaluates roads taking into consideration not only the age but the condition, the amount of traffic the roadway receives, safety and other factors. With a limited budget, the Town must prioritize roads and it is not always possible to pave roadways just based on the age. It is more cost effective to resurface a street before pavement deterioration becomes severe, requiring reconstruction.
Our program currently uses the following treatment types:
- Crack Seal – Cracks are filled with hot applied rubberized material to prevent water infiltration into the road base.
- Rubber Chip Seal – Application of a thin film of heated asphalt liquid is sprayed on the road surface, followed by the placement of small aggregates (“chips”). The chips are then compacted to orient the chips for maximum adherence to the asphalt, and excess stone is swept from the surface. This treatment adds strength to the existing pavement and can extend the life of the street by 8-10 years.
- Overlay – The highest form of street maintenance, overlay involves the placement of a new layer of asphalt, approximately one and a half inches thick, on the street. Properly maintained, an overlay can extend the life of the street by 20-25 years although heavily used streets may require more frequent overlays.
In the 1970s, Wellesley began using conventional chipseal as a regular part of the street maintenance program. While this program was successful and many streets still have this treatment as the wearing surface, this treatment was eliminated in the late 1990s due to complaints and negative mindsets. Only overlays were performed on any street in need of maintenance.
In 2008, the paving industry was greatly affected by the spike in oil prices, which have been high and unstable ever since. Oil is used in the production of asphalt.
In 2011, the Town re-evaluated the Resurfacing Program and investigated several other treatments including chip seal as alternatives to a strictly overlay program. The technological advancements in the equipment and materials significantly reduced the issues associated with chip seals. It was determined the Town would begin using Rubber Chip Seal, a newer technique, to expand the resurfacing program. Among the things rubber chip seal has going for it: low cost (one fourth to one fifth that of conventional asphalt overlay); eliminates need to crack seal; good skid resistance for vehicles; relatively non-disruptive to road drainage; uses recycled material; shorter construction times.
While the initial application produces a rough surface and some stray gravel is present, after a while it is hard to distinguish a chipsealed road from a paved one.”