Built in 1831, London Bridge was falling down by 1962. To make way for a new and bigger bridge, London sold its famous bridge to Robert McCulloch of chain saw fame, who had it disassembled stone by stone and rebuilt in his newly created desert oasis: Lake Havasu City, Ariz. Today, the resort town is halfway through its 11-year, $450 million conversion from septic tanks to a citywide wastewater treatment system. Photo: William D. Palmer Jr.
Bullhead City relies on the Colorado River, seen here in the distance, for water and recreation. Photo: City of Bullhead City
To handle the added capacity, the city is building one new treatment plant and has expanded two smaller plants that had primarily served local businesses. Because the new plant (and, at 3½ mgd, the largest; with plans to go to 14 mgd in four identical phases) is about 450 feet higher than the Colorado River, lift stations are being built to get the water to the new plant or divert it to one of the other two. All three plants treat effluent to a tertiary level and finish with ultraviolet treatment.
In this water-scarce area, flexibility is critical to managing what water a community does have. Because the city isn't allowed to discharge directly to the Colorado River, its goal is to recycle 100% of the effluent.
The Arizona Department of Environmental Quality recently granted permission to mix the A+-quality effluent from all three plants into a common reuse system. The plan is to inject treated water into vadose zone wells at the new wastewater treatment plant, creating a dome of water that flows down-gradient to a region between the plant and the lake where it can be recovered.
“If you do deep injection into the groundwater, anything you recover counts against your credits for water taken from the river,” says AMEC design manager Chris Hassert. “But if you get it from above the water table, it doesn't.”
In most cities, stormwater would be a concern. But not here. Since Lake Havasu City gets about 3 inches of rain a year, it has no traditional closed stormwater system. Instead, rain flows into inverted crowns designed into the roadway system and eventually discharges to Lake Havasu.Getting It Built
Each city took a different path—sometimes several—to building their new wastewater treatment systems.(To learn more about how the cities convinced residents, read Getting the Job Done.
Bullhead City tweaked the process for each of its three sewer districts.
For SID1 the city did the main line first, then the laterals. In some cases, however, the laterals had to be lowered because there was another outlet on the property.
For SID2, the city installed all the laterals first so the main line would go in with no problems. While that process worked better, the city had to come back later to disable the septic tanks and connect the service. This increased the amount of time crews spent working on private property, and homeowners complained.
Finally, on SID3, the city is doing the main line and the laterals at the same time with the on-lot crews following right behind, shortening the conversion process to within 30 or 40 days.
“We haven't found a magical solution, but we think we're close,” says Agrawal.