How Clark County Public Works improved an overloaded Wash Channel
By Brianna Fries
When one thinks of areas that are prone to flooding, Las Vegas doesn’t normally come to mind. That being said, Las Vegas is very vulnerable to flooding, as its desert environment can rapidly become overloaded with stormwater when the weather does produce a rare bout of rain.
The Las Vegas Wash in Las Vegas, Nevada, is a 12-mile long channel that feeds the area’s excess water into Lake Mead and currently carries up to 200 million gallons of treated wastewater and run off. It normally handles this water well, but in 2012 it was inundated by the region’s heaviest rainfall in 75 years. Within three hours, there was 1.65 inches of rainfall, resulting in the flooding of the golf course that sits at the junction of the Las Vegas and Flamingo washes, the flooding of surrounding homes and businesses, and at least one death.
Immediately, Clark County realized that something had to be done to avoid a repeated incident. The result was Las Vegas Wash Phase 1 Project, an improvement project that not only negated any future flooding issues, but even won the American Public Works Association 2017 Project of the Year award in the Environment category.
After receiving the Notice to proceed on the project in November 2013, Clark County Public Works decided to go with a Construction Manager At Risk (CMAR) approach for the project, getting the contractor onsite to begin working on the project sooner rather than later.
As Mamer explains, “In order to improve the channel, the public golf course within it would need to be reconstructed. By using a CMAR procurement method, the County was able to give the chosen contractor separate ‘early release packages,’ as plans for each of the various scopes of work were available. The first ‘package’ involved the initial grading of the site and the removal of several thousand yards of material to open up the channel. It also included removal of the Sahara Avenue Bridge, which was causing a bottleneck. As the design of the bridge structure and golf course were completed, those portions were subsequently negotiated and awarded to the contractor.”
Using the CMAR method saved both money and time. The result was that the project cost $97 million – a full $3 million under the GMP – and lasted only 751 construction days instead of the originally projected 806 days. More than half of the funding for the project came from the Regional Flood Control District.
“The primary goal of this project was to protect life and property by increasing the capacity to convey storm flows,” said Michael Mamer, Assistant Manager of Construction for Clark County Public Works. And that was exactly what the Las Vegas Wash Phase 1 Project did. Once the project was completed, gaining Final Acceptance in September 2016, it removed the majority of 1,700 homes from a flood plain area, providing them with physical protection from floodwaters and lowering the flood insurance premiums for the homes as well.
The Las Vegas Wash Phase 1 Project accomplished their goal of protecting life and property along with a lot more, including excavating an area of 450,000 CY; replacing the Sahara Bridge and two other pedestrian bridges; constructing a 20-foot wide concrete low-flow invert; reconstructing and up-sizing sewer mains from 24” to 104”; and reconstructing the existing maintenance facility and clubhouse.
Not only was the sod better equipped to handle reclaimed water, but the golf course’s whole design was improved too. The narrow course was redesigned to include a new fairway orientation and green locations that made the course more playable and enjoyable while decreasing any chance of damage being done to nearby homes.
One additional piece of the puzzle that Clark County Project Works had to deal with was the extra water from the nearby water treatment facility. Since the creation of the treatment plant, the water flow going into the wash had increased so much that the wash itself expanded due to erosion. The project team made sure to take this into account with their plans for the formerly flooded golf course. “In order to make use of the abundant effluent water from the nearby water treatment facility, the project installed a salt tolerant “Seashore Paspalum” sod on top of the Pyramat soil stabilization fabric,” detailed Mamer. “The specially grown sod handles the high salt content of the reclaimed water and requires only an occasional fresh water “flush” to thrive in the desert heat.”
Clark County is still looking forward to more improvement projects in their future, according to Mamer. He added that future projects include “the completion of the last few segments of the 56-mile long Clark County 215 Bruce Woodbury Beltway, multiple arterial roadway projects in the Las Vegas Valley, and a bridge in Laughlin, NV that will cross the Colorado River.”
Brianna Fries is an Assistant Editor for American Infrastructure Magazine. She may be reached at email@example.com