|
Reality: Non-Destructive Vacuum Excavation Saves Money
An ounce of prevention is worth a pound of cure. A Purdue University study found that for every $1 spent on SUE methods, $4.62 was saved.
The costs of obtaining QL-B and QL-A data, according to the Purdue study, were less than 0.5 percent of the total construction costs and resulted in a construction savings of 1.9 percent over traditional QL-C and/or QL-D data.
North Carolina’s DOT spent $10,000 but saved an estimated $500,000 using vacuum excavation for a project to locate a water line.
In Boston, vacuum excavation was used to verify locations on a $30 million utility project, which was part of a $14 billion Central Artery/Tunnel project. By spending $98,000, the contractors sleeved and moved about 37,000 ft of pipes, mains and ducts without damage or delay and found pipes that weren’t previously marked — finishing the job five months ahead of schedule.
There are hundreds, if not thousands, of positive examples like these.
Consider the size and cost of a typical contractor test pit. Most are 50 to 100 sq ft, whereas air vac test pits are 1 sq ft. In cities where a street opening permit costs $50-plus per square foot, vacuum excavation offers significant savings — not to mention that backhoes and excavators often require a lot of manpower, closure of streets and are not as environmentally friendly.
In some cases, vacuum excavation is half the cost of exposing the utility with a backhoe or excavator.
But what about hand digging? Well, if time is money, then hand digging isn’t necessarily cost-effective. And, there is the possibility that a shovel could hit and rupture or cut a utility. Air vacuum excavation is fast and properly operated, it will not damage a utility or the utility’s protective coating.
Why Don’t We Know What’s in the Ground?
According to Cost Savings on Highway Projects Utilizing Subsurface Utility Engineering, Purdue University, existing records of underground site conditions are usually incorrect, incomplete or otherwise inadequate because:
• They were not accurate in the first place. Design drawings are not as-built or installations were field-runand no record was ever made of actual locations.
• Multiple parties have been involved over the years. On old sites, there have usually been several
utility owners, architects/engineers and contractors installing facilities and burying objects for decades. Seldom are the records placed in a single fi le, and they are often lost. There is almost never a composite.
• References are frequently lost. Records show that an object is a certain distance from a building that is no longer there, or an object is a certain distance from the edge of a two-lane road that is now four lanes or is part of a parking lot.
• Records are often insuffi ciently maintained. Lines, pipes and tanks are removed from the ground but aren’t removed from the drawings.
|
|
