For at least 25 years, Nashua, N.H., has been replacing 7,500 triangular manhole covers with round ones. Like a circle, a Reuleaux triangle's constant width prevents the 150-pound cover from falling into the manhole. Even better, the covers point in the direction sewage flows.
These were probably compelling arguments a century ago when public works ordered the covers, which are 25½ inches at their widest point, from local manufacturer Nashua Foundries Inc. The automobile was relatively new, so the U.S. Occupational Safety & Health Administration had yet to require a cover to support at least twice a vehicle's applied axle load, or that sewer workers arm themselves against injury or death. Today, getting into those manholes is virtually impossible.
Street Superintendent Roy Sorenson told the local newspaper last summer that his team replaces 100 or 200 covers every year in the course of regularly scheduled maintenance and repaving. With an estimated 2,000 left to go, he and his team have at least a decade more work.
|50/50 VIRGIN/RECYCLED RUBBER ROAD SMOOTHIE|
What it is: Custom-made cover cut to any shape or size (including square and triangular) that's glued to the lid or entire frame to raise manhole ½ to 3 inches. Depth also can be customized to accommodate uneven settling.
How it works: Warm manhole cover, spread adhesive on cover, place product
Point of distinction: Only solution for gaps 1 inch or smaller; can be recycled with asphalt; can be engraved with city or business name/logo; guaranteed to outlast surrounding pavement; approved by CalRecycle of California
Required tools: Blow torch, Underground Technologies' Secure N Seal adhesive
Price range: Starts at $110 each
Ordering/availability: Direct from manufacturer (contact information on website); usually delivered within three weeks
Manufacturer: International Road Rubber; West Jordan, Utah, www.roadsmoothie.com
Water Systems/Sanitation/Public Transportation Superintendent
U.S. EPA estimates the number of sewer manholes nationwide to be 12 million. Most coincide with the typical lengths of city and suburban blocks — about 300 feet apart — but distances between structures range from 100 to 500 feet. Regardless of their relationship to each other, though, 80% are in some state of disrepair.
It's tough to calculate the true cost of raising a manhole, but to help current and potential customers compare the life-cycle costs of various options riser manufacturer American Highway Products Ltd. of Bolivar, Ohio, analyzed interviews with 30 paving maintenance supervisors and contractors to develop a checklist:
- Material. Irrelevant unless labor's included. Precast concrete risers, for example, are relatively inexpensive but equipment- and labor-intensive.
- Labor. Look at time logs and maintenance reports. For example, at one time Shoreline, Wash., would pave over manholes, then go back and jackhammer the new pavement to dig out and raise the frame with precast grade rings. The wastewater manager analyzed three years of maintenance records to calculate per-structure material and labor costs of $500.
|100% RECYCLED RUBBER EASY-RISER|
Concept: Instead of raising the manhole frame to the level of new pavement, this two-piece rubber mat goes on top of the existing cover to substitute for the overlay at the manhole. Fits manholes up to 26 inches in diameter; withstands temperatures up to 500° F.
How it works: A cut-and-paste job that's like making and placing a two-piece puzzle. Cut the material to fit, position with the company's double-sided adhesive tape, and pave (after telling the operator to raise the paver slightly at manholes to avoid grabbing the mat's edge and moving it). The pressure bonds the mat around the cover to the pavement while leaving, as Fast Company magazine described in 2010, a removable “inner piece held in place by a tongue-in-groove/reverse bevel system.” Pry up with crow bar or screwdriver to access manhole below.
Point of distinction: Only “no-leak” riser; can be recycled with asphalt
Required tools: Utility knife, leaf blower, marking crayon, acetone, rags, rasp, pry bar or large screw driver, Easy-Bond double-sided adhesive sealant tape; if necessary, ½-inch Easy-Shims to raise the 1½- or 2-inch mat to overlay level
Price range: $119 to $148 each
Ordering/availability: Direct from manufacturer (see website for contact information); usually ships within two days
Manufacturer: Utility Cover Systems LLC; New Hartford, N.Y., www.utilitycoversystems.com
In a similar scenario, the City of Ontario, Calif., found that per-structure labor costs were $360 when using pre-cast grade rings.
- Liability claims. Bent rims; broken wheels, axles, struts, springs, steering linkages, etc.
- Pavement damage. The chance that a hot-mix patch doesn't bond well or rests on insufficiently compacted fill, setting the stage for subsidence that causes pavement cracks and uneven manholes.
- Inflow and infiltration. A decade ago, EPA estimated that upgrading treatment plants to eliminate the nation's 40,000 sewer overflows every year would cost $88 billion. The agency believes about one-third of the rain that causes them enters wastewater systems through the top of the manhole around the cover.
- Sustainability. Digging up and resetting utility frames unearths 500 to 1,000 pounds of material that, if contaminated, must be hauled to an appropriate disposal facility. Other energy costs: jackhammering, infilling with new asphalt, riser shipping.
- Lane closures: Any procedure that extends the duration of or requires future closures inconveniences the public. (And you know what that means.)
- Employee safety. Raising manholes during paving lessens the chances for traffic-related injury. Also, look at worker compensation claims related to lifting, crushing, or pinching when risers are delivered, racked for storage, loaded into trucks, and when carried to the utility frame and set into place.
Finding an easily installed and long-lasting riser is more important than ever. We hereby share these three potential solutions. For more information and to watch videos that show how each solution is installed, visit each company's website.
|EXPANDABLE-METAL PIVOTED TURNBUCKLE RISER|
What it is: Galvanized-steel insert manually tightened into place against the manhole frame to create a new, higher lid for the cover.
How it works: A gap in the one-piece insert is connected by a turnbuckle with pivots on each end. Insert a screwdriver in the turnbuckle and turn. Each rotation exerts 1,000 pounds of force, which is how one person achieves an air- and watertight seal around the frame's entire circumference. The full-circle “fuse” of riser to frame keeps traffic from dislodging or dislocating the cover.
Point of distinction: Because they're installed as part of the paving process, with crews placing the insert and manhole cover before asphalt is placed, the company says the product reduces costs 81%.
Required tools: Crowbar or pry bar, sledgehammer, Phillips-head screwdriver
Price range: Depends on diameter and height, but typically $100 to $150 each
Ordering/availability: Company website has a downloadable one-page order form that walks you through the process of measuring the existing frame to ensure proper fit; standard delivery is five days, but same-day service is available at no additional charge if the order is placed by 10 am EST.
Manufacturer: American Highway Products Ltd.; Bolivia, Ohio, www.ahp1.com