Without ample drinking water, growth in Northwest Arkansas would dry up faster than a salt flat playa.

The availability of clean drinking water is responsible in no small part for the area’s extraordinary growth. OK – Walmart’s expansion has also been a big catalyst for growth. But back in 1950, when Sam Walton opened Walton’s 5 & 10 in Bentonville, fewer than 90,000 people lived in Benton and Washington counties, located in the northwest corner of the state.

As Walmart grew (and grew and grew), so did the number of people in the area. (Two other Fortune 500 companies – Tyson Foods and J.B. Hunt – helped fuel the growth also.) According to the U.S. Census Bureau, the population of Benton and Washington counties in 1980 topped 180,000. Today it sits at 531,000. By 2045, nearly 1 million people are expected to live there, according to a study from the state’s Economic Development Institute at the University of Arkansas at Little Rock.

So, how do you deliver plenty of drinking water for another half-million people? You plan. Years and years in advance.

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YEARS IN THE MAKING

The formation of Beaver Lake in the 1950s and the creation of Beaver Water District (BWD) played a major role in how the area was developed. The lake was formed by damming the White River, and BWD was created to contract with the U.S. Army Corps of Engineers for water storage rights, produce clean drinking water, and disperse that drinking water to nearby communities. BWD has been working for decades with engineers, including the late Carl Yates and now with Olsson since the firm purchased McGoodwin Williams & Yates in 2018, to come up with a long-term solution to meet future demands for drinking water in the area.

“I think we’ve done a great job of being proactive and preparing for this growth,” said Lane Crider, chief executive officer of BWD. “There are always challenges in communities that are growing when it comes to things like transportation, utilities, and water. We’ve been very forthcoming in preparing for these kinds of challenges.”

Olsson started working nearly a decade ago on the water district’s Western Corridor project that will eventually deliver plenty of water through a BWD-owned treated-water line that provides a new distribution location for its four customer cities (Fayetteville, Bentonville, Springdale, and Rogers).

The Western Corridor treated-water line will mark the first time BWD has owned infrastructure outside of its current water treatment plant site. Currently, the district treats water sourced from Beaver Lake, and its customer cities own and operate transmission lines to the district’s treatment plants.

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PROJECTING FUTURE DEMAND

In 2019, Olsson was authorized by BWD to update its master plan’s projected water demands and evaluate capacity of a proposed waterline to be constructed for the western region of BWD’s service area. Based on the master plan, district officials decided the best way to keep drinking water freely flowing to the area was to build a transmission line to the west of Interstate 49. The line will start at BWD’s water treatment plants and flow to a new high service pump station about 7 miles to the west. The four customer cities will build transmission lines to hook up to BWD’s new pump station to support the significant increase in drinking water demands west of the interstate.

Chris Hall, leader of the Olsson Water/Wastewater team based in Fayetteville, was instrumental in figuring out exactly what BWD needed to supply water to a half-million more people. Using a hydraulic water model that included water infrastructure from BWD’s four customer cities, Chris sized the future treated-water line to meet the future demands for the people who will rely on BWD for their drinking water.

Chris and his staff met with representatives from each customer city and reviewed their most recent water master plans. By doing this, Olsson was able to identify key infrastructure improvements that needed to be included in the hydraulic model to assist with the conveyance of water to each of the four cities’ customers.

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CREATING A PLAN

The hydraulic water model included scenarios for current and projected service area demands. Future scenarios were created for the average and maximum water-use days in five-year increments from 2025 through 2040. The model revealed that the projected 20-year flow through the Western Corridor project could reach approximately 52 million gallons of water per day.

Chris and his team determined that a nominal pipe diameter of 60 inches was necessary to meet the demand of the 20-year design horizon while still providing BWD with operational flexibility should demands be higher than anticipated.

“Mainly, we looked at how we could maintain water quality and still meet demand,” said Brad Hammond, Olsson’s Fayetteville office leader who has worked with the district for more than two decades. “It’s always a balance between having enough capacity and keeping the water fresh because if you’re out of balance, either you can’t satisfy demand, or the water quality suffers. So, we had to look at not only capacity but also the age of the water and the potential effects that it might cause for the customer cities.”

Olsson confirmed an earlier recommendation to use a single pump station building to house all the pumps for the four customer cities rather than having each city operate its own. This design conserves space, is easier to operate, and cuts costs for the district and each customer city.

“Our mission is to provide clean, safe drinking water to our customers, and we can’t be put in a situation where we’re not able to meet a peak day or peak hour of demand,” Lane said. “We’re making sure we can deliver what our customer cities need when they need it.”

Olsson worked with Carrollo, the prime consultant on the original transmission line route study in 2011, to determine the most efficient path for the Western Corridor treated-water line. Our Water/Wastewater team began developing easement documents as BWD started to acquire the land for easements after the route was finalized.

“Corridors here are closing fast, and to find room for a large pipeline like this is getting harder to come by because of the growth,” Chris said.

Olsson is serving as prime consultant for the treated-water line and is working with prime consultant Black & Veatch in the design of the pump station. Construction on the transmission line is scheduled to begin in the summer of 2023 and is expected to be completed by January 2026. The cost for both the treated-water line and pump station is estimated to be about $115 million.