The Springfield Water and Sewer Commission in Massachusetts provides almost 36 mgd of drinking water for 250,000 people. The largest city along the Connecticut River, some of the community's 37 miles of water infrastructure dates back to 1848.
After the river overflowed in 1936, the U.S. Army Corps of Engineers (USACE) installed an expansive control system that's deterred flooding since. Recently, though, sinkholes in the vicinity of the floodwall hinted that four of the city's five 80-year-old transmission mains were on the verge of failure. Subsurface investigation showed the 30-inch lock-bar steel pipes were entangled in the usual rat's nest of infrastructure. All four crossed beneath the river, two crossed under the floodwall, and two passed under railroad tracks.
To expedite the design and regulatory approval processes, the city retained the Cambridge, Mass., office of construction management and engineering design consulting firm Kleinfelder. Firm engineers developed an 11-phase construction sequence using Autodesk Inc.'s AutoCAD Civil 3D software to demonstrate existing conditions and then create visualizations of each proposed construction phase activity.
Once the digital terrain models and other necessary background information were gathered, the firm completed the design phase modeling activities over the course of one year from 2009 to 2010.
The first six months were spent developing documents to the 60% design phase and presenting them to USACE. The remaining six months included several meetings and review cycles with the agency to address comments and concerns and advance to the 100% design phase. Design, review, commenting, and approval periods were all factored into the original schedule.
Regulatory approval took about six months.
The project was substantially complete within one year, which was on schedule according to the contract.
- Original bid price: $3,437,000
- Change orders: $278,000, $48,000 of which was new work initiated by the owner, totaling 8.1% of the original bid
- Change orders related to construction conditions: $230,000, or 6.7% of the bid price
- Consulting fee: approximately $395,000.
Though it's difficult to predict what the change-order values would've been without the modeling, the process demonstrated the value of proper planning. There were no differing site conditions or delays due to actual field conditions that weren't originally anticipated in the modeling phase.