Study outlines 4 options to expand city water supply
A water study commissioned by the City Council has partially analyzed four options for expanding Lawton's raw water supply.
Council members received a briefing Wednesday on a draft copy of that study, "draft" because data still is needed to fully analyze planned indirect potable reuse, direct potable reuse, groundwater and river bank filtration, then prepare recommendations on how those options could be used to supplement the raw water now supplied by the city's surface sources: Lakes Lawtonka, Ellsworth and Waurika.
Indirect and potable reuse means reusing treated effluent from the wastewater treatment plant, either by transporting the additionally treated effluent to city lakes (indirect) or to the water treatment plant (direct). Groundwater means taking advantage of the Arbuckle-Timbered Hills aquifer under Comanche County via water wells, while river bank filtration means drilling wells near East Cache Creek, then filling them with treated effluent that would seep through the East Cache Creek alluvial before flowing into the creek.
While test scenarios still are needed to fully evaluate the indirect and direct potable reuse options, the largest segments of missing data are associated with groundwater options because engineers must wait until test wells are drilled before obtaining the water quality and quantity data they need to complete the analysis, said Michael Graves, the lead engineer for Garver, the firm that has been tapped to handle the alternative water sources study that may not be fully completed until late 2016.
City officials have said the findings in that alternative water sources report remain critical, even though heavy rains in May filled lakes in the region and moved area out of historic drought, because drought in Oklahoma is cyclical and it eventually will return. The idea behind the water study is to find water supplements, providing an additional 5 to 10 million gallons a day (mgd) and giving Lawton-Fort Sill a more resilient water supply, according to the Garver study. That study notes 5 mgd is to come from groundwater sources and up to 5 mgd from reuse options.
The council hasn't made any final decisions and Garver isn't ready to provide recommendations on all four options but members did indicate Wednesday that city administrators should continue with plans to designate funding to drill 10 test wells for the groundwater option, a cost estimated at $1 million last year when city officials discussed funding the activity through the 2015 Sales Tax Extension.
Graves said groundwater is an option because of the amount of water in the Arbuckle-Timbered Hills (ATH) aquifer, which state officials say contains 429,800 acre feet a year (384 million gallons per day) of water available for permit. But there are only 5,300 acre feet per year (less than 5 mgd) permitted and that might be because of problems with fluoride and total dissolved solids, Graves said, noting the median fluoride content of existing wells is 9.1 milligrams per liter, when existing secondary standards are 2 mg per liter. That level has been consistent in reports dating to the mid-1970s.
"It's a water quality issue," Graves said, adding that engineers can't pull extensive data because of the lack of active wells, noting there "just is not a lot of data out there."
Fluoride counts from existing wells range from 8 to 12 mg per liter, while total dissolved solids range from 600 to 800 mg per liter (the standard is 500 mg per liter).
Despite potential quality problems, engineers say the water is worth researching. There are 25 existing wells in the ATH aquifer in Comanche County, with depths of at least 500 feet. Two of the deepest within Lawton are at Great Plains Technology Center (1,200 feet, with a flow of 450 gallons per minute) and one drilled by the Comanche Nation at the Comanche Nation Water Park (800 feet, with a flow of 600 gallons per minute).
Lawton's best option is to drill test wells to determine water quality and quantity, and Garver has identified 10 test sites within or just south of the city, including three in southeast Lawton convenient to the water and wastewater plants. Graves said the best way to evaluate the water is onsite hydrogeological and geophysical investigations, then drilling test wells. Data revealed by those activities will allow engineers to design treatment options, he said, noting treatment could be at each wellhead, centralized (locating a treatment facility convenient to several wells) or blending well water into the city's distribution system or its surface water sources.
But engineers won't be ready to make any recommendations until they have completed analysis, Graves said, noting engineers need "hard, quality data."
"We have hard data on IPR and DPR options. Not here," he said.
Among those recommendations will be how to best use the water: in the drinking water system or non-potable uses (not for human consumption). Great Plains Technology Center uses its well for irrigation because its fluoride content is too high for it to be feasible for consumption.
Test wells of a lesser depth are need for river bank filtration, an option that relies on nature in this case, materials deposited under and around the bed of East Cache Creek to filter effluent that is pumped into wells drilled 25-50 feet from the creek. That effluent water ultimately would seep into East Cache Creek, where it would mix with creek water, then be drawn out for treatment.
Graves said options would include horizontal or vertical wells, and determining where the wells would be placed. For example, the farther away the well is from the creek, the less water would make its way through the alluvial. But that water would be better quality because it seeps through more alluvial. More water would find its way into the creek from wells drilled closer to the creek, but water quality would be poorer because it would seep through less alluvial.
Graves said Garver must continue collecting and analyzing data, noting the most pressing need is test wells for the groundwater options. He said drilling those wells would take four to five weeks, with analysis and final data production taking another four to six months. Given the time frame needed for the investigation, drilling and analysis, Graves said it would be August to November of 2016 before Garver's final report is ready.
Additional testing data also is necessary for the reuse options, which would let the city take advantage of treated effluent from its wastewater treatment plant southeast of town.
That facility has a design capacity of 18 mgd, but treats an average of 10 mgd. City officials say that 10 mgd is constant; unlike potable (drinking quality) water, which fluctuates depending on the time of year, wastewater produces an almost constant 10 mgd stream. About half is obligated to AEP-PSO for the cooling pond it maintains for its energy plant near Lawton's wastewater plant. The remainder of that treated effluent is dumped into Nine Mile Creek and it is that water the indirect reuse, direct reuse and river bank filtration options seek to divert for new use.
Indirect potable use is a planned system of directing treated effluent to a surface water source, but that option means upgrading the city's water treatment plants to provide more advanced treatment and waiting for state law to catch up with the application.
Garver's report says the treated effluent now discharged into Nine Mile Creek (where much is lost to evaporation, city officials say) could be discharged into Lake Ellsworth or Waurika Lake. The exact point of discharge was another bit of data analyzed by Garver engineers, who recommend the city discharge the water into Ellsworth because that lake is wholly owned by the City of Lawton. Waurika is shared by six communities and the other five would have to agree to the plan and it "could be a challenge to meet the needs of all cities," Graves said. Officials also would have to decide how Lawton's action to add 5 mgd to the lake each day would be factored into its formula for removing water from Waurika Lake, Mayor Fred Fitch said.
That option as well as direct potable use is complicated by the fact that Oklahoma does not have regulations governing those processes, although study committees are working through the Oklahoma Department of Environmental Quality and Oklahoma Water Resources Board to craft regulations that will govern removal of specific contaminants, including pathogens. Garver said while no regulations exist for indirect reuse, the state will consider the issue on a case-by-case basis, although there also are existing prohibitions on augmenting sensitive water sources (all three Lawton lakes carry that designation).