Constructing a wetland near a river is tough, muddy work – especially during the winter. That's why harsh conditions were a top consideration for Scott Smith, senior lead and street supervisor for the city of Prineville, OR, when he rented equipment for the Crooked River Wetland Project.
This $350,000 wetland restoration project funded by the Oregon Department of Transportation was designed to do several things: to rehabilitate land for the city's wastewater treatment plant expansion, to replace wetlands disturbed by state road construction, and to minimize the environmental impact of residential and commercial development.
It also addressed other infrastructure challenges that had taken their toll on the river's ecosystem. After the area flooded in 1964, the river was straightened and channelized, and much of the riverbank vegetation was lost. Dams built on both the Crooked River and the Ochoco Creek also altered the river's path. Since then, the river's increased velocity has resulted in erosion – as well as more vegetation loss and downstream flooding.
In November 2005, the city of Prineville and ODOT began reconstructing 10 acres of wetland along a 2-mile stretch of the Crooked River, near the Deschutes Basin – a degraded, low-lying area ideal for establishing a wetland hydrology. It took crews 33 days to complete 3.5 acres of excavation work using a rented excavator and two articulated trucks.
“During this phase, the site was excavated down an average of five feet to existing groundwater elevations,” Smith recalled. “The crews moved approximately 33,000 cubic yards of material, which we are using to construct a 60-acre wastewater holding pond.”
Construction for phase two began in November 2007. This phase included a 6.5-acre wetland near O'Neil Highway, just upstream from the phase one site. Phase two was slated to last more than three months because city crews were plowing snow and sanding the roadways in addition to performing their construction duties.
“Also, ground conditions during this construction phase were very muddy and wet, which we anticipated would slow down our progress,” Smith said.
When Smith asked for phase two bids, he required equipment dealers to supply the city with late-model, low-hour machines that were comfortable for his crews to operate for long periods of time. He also needed to rent the equipment by the hour rather than by the week or the month to accommodate his crews' work schedules.
Triad Machinery in Prineville had the winning solution with an excavator and three Terex articulated trucks. The Terex articulated haulers – a TA35 and two TA30 models – were chosen for their increased fuel efficiency and their Tier-III engines' lower emissions. These haulers have an independent front suspension system, which ensured that Smith's operators would enjoy a smoother, more comfortable ride and improved handling. The haulers are also equipped with all-round, fully enclosed wet-disc brakes on all wheels, giving Smith's crews the advantage of fade-free braking.
“The ground conditions aren't very good when you're constructing a wetland near a river, especially during the winter months,” Smith said. “So the equipment, particularly the haul trucks, had to work through every condition without getting stuck or beating up the drivers.” According to Smith, for more than 40 days during phase two construction, the trucks were pushing mud with their front bumpers the entire length of the half-mile haul road.
Excavation depths for the second wetland area averaged 8 feet throughout the site, producing about 98,000 cubic yards of material. Together, the excavator and articulated trucks moved an average of 1,500 bucketfuls – or 30 truckloads – of excavated wet, dense clay every day, which was hauled about 2,500 feet to a stockpile area. Smith says this material is also being used for the construction of the city's new wastewater holding pond.
Scheduled for September 2008, the final phase connecting the wetland to the Crooked River was expected to take three days to complete. The newly constructed wetlands will be home to several sensitive and federal ESA-listed species including redband trout, Pacific lamprey, western toad, Oregon spotted frog, bald eagle, pallid bat, and long-eared myotis bat.
Smith reported that the project has received rave reviews, winning more than 30 awards. In fact, the project has been so successful, the city has already agreed to a similar project downstream. With today's focus on the environmental impact of development, it's a real reminder of how construction can be used to not only transform but also restore the natural landscape.
|Amber Reed and Camille Wolfe are writers for Performance Marketing, West Des Moines, IA. Story provided by Terex Construction Americas.|