Twenty Mile South Biosolids Application Site


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The city of Boise owns and operates a 4225-acre farm on South Cloverdale Road, approximately 20 miles south of Boise. The "Twenty-Mile South Biosolids Application Site" (TMSBAS), receives the "biosolids" from the City's two main wastewater treatment plants (WWTPs): Lander Street and West Boise.

Dewatered biosolids are trucked to the site in trailers that hold approximately 30 wet tons per load. The treated biosolids are stored, then applied to fields for growing forage crops that are eventually sold to farmers. The site is managed to comply with all Local, State, and Federal regulations governing the reuse of biosolids.

In addition to irrigated fields, the TMSBAS has constructed a new facility which consists of an office building, maintenance shop, parts warehouse, and mechanic shop. This new facility has been designed to receive LEED GOLD certification, in addition to becoming the first commercial zero net energy facility in Idaho. The intent of this upgraded facility is to offset the energy consumed on-site with energy produced on-site, using solar panels, and operating more efficient heating and cooling systems.

In 2014, TMSBAS received an "Excellence in Biosolids Management" Award from Northwest Biosolids and the Pacific Northwest Clean Water Association. The award recognized TMSBAS for its significant contributions in implementing a cost-effective and environmentally beneficial biosolids management program. In the 27-year history of the award, Boise was the first recipient from Idaho.

Why Recycle Biosolids at the TMSF?

Biosolid App

  • Biosolids are valuable fertilizer. The biosolids help replenish the soil nutrients that have been removed by the crops grown at the TMSBAS. With ample amounts of nitrogen, phosphorus, and potassium contained in the biosolids, Boise City doesn't have to buy as much commercial fertilizer, resulting in substantial cost savings for the farm.

  • Boise City strives to demonstrate that we are good stewards of the TMSBAS and we manage biosolids in a manner that is environmentally sound, technically feasible, cost effective, and socially acceptable. By overseeing the entire “cradle to grave” process of the biosolids land application program, the City has minimized regulatory liability by ensuring that all local, state, and federal requirements are met. Almost as important, the City directly receives the revenue that is produced by growing high quality crops on the farm land. This revenue is returned to the sewer fund which helps to keep rates low for Boise City’s rate payers.

  • Biosolids provide organic matter to improve soil structure and help increase water holding capacity. Another added benefit: using biosolids as a soil amendment keeps the product out of the landfill, saving worthwhile landfill space.

How it Began

Prior to 1993, Boise City administered a land application program whereby local farmers would enter into contracts that would allow liquid biosolids to be applied to private farmland. The parcels located closest proximity to the West Boise WWTP received priority for biosolids applications and the City applied year-round. In 1993, EPA made land application rules more stringent. At the same time, the Treasure Valley was experiencing significant growth. Areas traditionally used for agriculture were being encroached upon by urban development.

Seeking a permanent solution, Boise City purchased 2325 acres of farmland for biosolids application in 1994. then began growing crops: primarily, alfalfa, corn, and small grains. Over the years, additional acreage was purchased to bring current farm acreage to 4225 acres.

Over the past 20 plus years, the TMSBAS has proven that the foresight of City leadership in the early 1990’s was very sensible. In Idaho, approximately 60% of municipal biosolids are land applied so what the Boise City is doing at the TMSBAS is not unique. What is somewhat unique is that the City owns and operates the entire facility, from the biosolids transport, storage, and application to soil preparation and tillage, to planting and harvesting the crops. The wheat combining and silage corn chopping are completed by outside contractors each season, but the City performs all other farming duties.

For More Information or to Schedule a Tour

Ben NydeggerBiosolids Program Manager
Phone: 208-608-7446