"We have seven crews tackling different project components, managed by a lead superintendent with two assistant superintendents and seven foremen," says Wellman, adding there have been no lost-time accidents thus far and construction remains on schedule. "We hold weekly subcontractor and owner progress meetings that review detailed three-week schedule look-a-heads. There are also pre-activity meetings for large construction events, including continuous concrete pour marathons."

Flood Season

Preliminary construction began in January to expedite work within the channel prior to flood season, which occurs from July through September. A network of 12 high-head diversion pumps and pipelines reroute water runoff while channels are lowered 15 ft, with 2,700 linear ft being lined with layers of grass turf, reinforced concrete and woven polypropylene geotextile material for added structural stability and reduced soil erosion. Roughly 63% of project channels are being recontoured into trapezoidal-shaped drainage. Viking Drillers Inc., Granite Bay, Calif., is the dewatering subcontractor.

The previously earthen, mostly unlined, open channels contained buried garbage that was only discovered once excavation began. Las Vegas Paving removed 5,100 truckloads of discarded golf balls, shopping carts, concrete, wood and cable. Put in perspective, the trash was enough to fill 255 swimming pools. Screens, weirs and filters are being added to limit accumulation of future pipeline clogging debris while improving maintenance access. There are 15 variously sized inlets emptying into the washes, the largest coming from Christy Lane.

"A big portion of the Las Vegas valley drains down to this area," says CH2M-Hill project manager Ken Gilbreth. The project will produce a threefold improvement in stormwater flow, he says.

But capacity expansion is tricky due to congested surroundings that require the relocation and replacement of two 180-ft-long, 12-ft-wide prefabricated steel pedestrian bridges, plus a third smaller crossing, all made by Las Vegas-based P&S Metals and Supply Co. Also, the 19-year-old, 133-ft-long Sahara Avenue Bridge over the Las Vegas Wash is being demolished and rebuilt. The four-lane crossing carries about 26,200 vehicles a day between Sloan Lane and Winterwood Boulevard.

Hydraulic excavators with hammer and shear attachments are tearing down the three-span structure piecemeal. The 104-ft-wide prestressed concrete replacement maintains the same grade elevation but with a deeper wash channel and repositioned center pier. Sierra Ready Mix LLC, Las Vegas, is providing the bridge and project concrete, totaling 35,000 cu yd, including cast-in-place channel and headwalls, foundations and miscellaneous structures.

Another wash widening hurdle lies with a 15-in.-dia sewer line, owned by the Clark County Regional Flood Control District, which requires 5,500 linear ft of relocation. The outdated line is being replaced and expanded with up to 48-in.-dia pipe.

The City of Las Vegas, similarly, has a sewer line impacted by the wash expansion that is receiving a realignment and capacity upgrade. The 10,800-linear-ft project places up to 104 in. dia of glass-fiber-reinforced, polymer mortar pipe, manufactured by Austria-based HOBAS, making it Southern Nevada's largest sewer line.