The city of Post Falls expects to spend $30 million over the next six years on upgrades to its waste-water treatment plant to meet stricter environmental standards and to handle the citys growth.


The city also tentatively plans to spend another $7 million in the three years after that on a project that would enable it to irrigate land it owns on the Rathdrum Prairie with treated water from the plant, says Terry Werner, public works superintendent for Post Falls.


Last month, Post Falls hired the Coeur dAlene office of Boise-based J-U-B Engineers Inc. to design the improvements in the first $30 million of work, which would be done in stages between now and 2012, says Werner. That design contract will cost $900,000, he says.


Our understanding from the U.S. Environmental Protection Agency is that our future permit to discharge treated water into the Spokane River will require us to release 50 micrograms or less of phosphorus per billion particles of outflow into the river, Werner says. If that changes between now and 2012, well have to reevaluate where we stand.


New filtration options designed primarily to remove phosphorus from waste water likely would be installed at the plant at a cost of at least $11 million at the end of the six-year, $30 million project, Werner says.


The $30 million in improvements would expand the plants capacity from its current maximum of treating 3.1 million gallons of waste water a day to treating 5 million gallons a day.


The proposed filtration systemwhich might include membrane filters, fine-sand filters, or even technology that has yet to be inventedwould enable the plant to discharge into the Spokane River whats classified as Class A water, Werner says. Although not approved for human consumption, Class A water is considered safe for contact with humans and is used to irrigate golf courses.


The plant currently releases into the river Class C water, which can be used to irrigate food crops, such as carrots and potatoes, as long as the water isnt applied directly to the edible part of the plant, says John Kendall, staff engineer for the Coeur dAlene office of the Idaho Department of Environment Quality.


The planned expansion would provide the plant with enough capacity to meet Post Falls growth needs for the next 20 years, says Werner. In addition to serving Post Falls, the plant also treats waste water for the city of Rathdrum under contract, and the expansion would meet Rathdrums expected growth needs as well, Werner says.


Currently, the plant averages a flow of 2.4 million gallons of waste water a day. Werner says daily flows into the plant have increased by an average of 100,000 gallons each year over the past three years, and he expects those flows will continue to grow as Post Falls and the surrounding area grow.


The planned improvements at the plant likely will be done in three phases: generally upgrading equipment to stricter standards; building new and expanded concrete basins to increase the plants oxidization and aeration capacities; and making filtration upgrades, which would also include expanding the plants ultraviolet disinfection capabilities.


Within the next two or three months, some work could be done on equipment upgrades, such as on clarifiers, and on oxidation ditches, he says. In the second phase, bids for work on the concrete basins would likely be sought early next year. As part of that phase, the oxidation-ditch improvements would be scheduled to be completed in 2008.


The design and installation of filtration systems likely would take place in 2010 and 2011, he says, with the plant reaching in 2012 the planned capacity of being able to treat 5 million gallons of waste water a day and also remove phosphorus from the treated water.


A $100,000 pilot study of irrigating the Interstate 90 right of way between the plant and the nearby freeway with treated waste water will be included in the second round of the work.


That pilot project, if it goes forward, would be a precursor to the long-range proposal to pipe irrigation water onto the Rathdrum Prairie.


Werner says the city currently has $18 million in its capital fee fund, generated by new hookups to its waste-water system, plus $12 million in its operation-maintenance replacement fund, and thus already has enough money to pay for the first $30 million in planned upgrades. He adds that user fees are adjusted annually to meet increases in expenses such as to buy natural gas and to pay personnel at the plant, but those fees wont be increased to help pay for the plants proposed expansion.


Contact Rocky Wilson at (509) 344-1264 or via e-mail at rockyw@spokanejournal.com.