Watershed Planning and Restoration Program
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Water Quality
TMDL Studies: Overview | Little Cottonwood Creek | Alta Fen | Jordan River | Emigration Creek
Alta Fen Pilot Project
Background
Media Placement at the
Alta Fen Pilot Project site.
In 1996, Salt Lake County began construction on a pilot project to build a constructed wetland for pollutant removal in Alta, Utah. This project utilized a fen for adsorption and bioaccumulation of metals, thereby reducing the metals load in Little Cottonwood Creek.
In addition, the fen has been used to neutralize pH levels in the Creek. The fen has been in operation for the last nine years with repeated monitoring.
Recently, the United States Geological Survey (USGS) has been contracted to create an OTEQ model to determine if the Fen has the capacity to treat the entire Columbus-Rexall Mine Drainage. In order to treat the entire discharge, the fen would be deepened to accommodate increased removal capacity.
FAQs
What is a fen?: A fen is a specific type of wetland normally occurring in montane to sub-alpine ecological settings. Fens, generally have waterlogged, spongy ground containing alkaline decaying vegetation. The vegetation is typically dominated by rushes or sedges, which over the centuries may develop into peat. Many fens in the Rocky Mountain Region are as old as 14,000 years—dating to the Holocene and Pleistocene eras—which were created shortly after glacial retreat.
What is absorption?: Adhesion of the molecules of gases, liquids, or dissolved substances to a solid surface, resulting in relatively high concentration of the molecules at the place of contact; eg the plating out of an anti-wear additive on metal surfaces.
What substrate material was used to create the fen?: The Salt Lake City/County joint landfill composts yard waste such as trees, shrubs, and other wood products such as pallets. Large quantities of wood are composted at three grade variations, based on different levels of screening. The finer screened material possesses fiber sizes and traits similar to peat. This material is also free of background metal contaminants and is very high in organic matter. In order to minimize cost, compost from the Salt Lake City/County landfill was used for substrate material.
How does sediment trapping work?: High sediment loads from storm events was minimized with the addition of a pre-cast concrete box which housed a V-notch weir and a compartment for sediment deposition and removal. However, since the fen has been in operation, lilltle deposition has actually occurred in the box.
Reports
Since development of the fen in 1996, extensive water quality data (i.e. pH, Dissolved Oxygen, Temperature, Conductivity, Sulfate, Hardness, Total Cadmium, Total Copper, Total Lead, Total Zinc) has been collected to determine the efficacy of this project. The results from those studies are summarized in the following: