Timiline of Tibble Fork Reservoir Sediment Release

In an effort to keep residents informed on the situation with water coming from American Fork Canyon, the city has put together the following timeline. We will continue to update this as new information is received.

August 20, 2016 – During a dam rehabilitation project being conducted by North Utah County Water Conservancy District, a large release of sediment from Tibble Fork Reservoir is sent down American Fork Canyon via the North Fork American Fork River.

August 21, 2016 – Cedar Hills staff observes discoloration and high levels of turbidity in golf course pond 10, which serves as a retention pond for the city’s pressurized irrigation system. Staff makes a call to Pleasant Grove Irrigation Company, the utility company that controls the city’s water source from the Canyon. They indicate that the event is nearly over and that the water would clear up shortly.

August 23, 2016 – The Division of Water Quality (DWQ) is notified of a large release of sediment from Tibble Fork Reservoir into the North Fork American Fork River. That same day, DWQ begins to collect water and sediment samples to determine the water-quality impacts from the release. DWQ analyzes the water chemistry and sediment samples for a broad range of heavy metals and screened the findings against recreational, agricultural, and aquatic-life criteria. A few weeks later DWQ issues a report with their findings, and states:

Concentrations of total metals in the water column in samples collected August 23, 2016, through August 30, 2016, below Tibble Fork Reservoir do not exceed human health screening values for recreational exposure. Concentrations of dissolved metals in the water column in samples collected August 23, 2016, through August 30, 2016, do not exceed screening values for agricultural or aquatic-life use.
The UCHD collected samples from Highland Glen Reservoir, Heritage Park, and Manila Reservoir on August 31, 2016, in response to concerns about the quality of irrigation water used downstream. Analysis of total and dissolved metals concentrations in samples taken at these locations confirmed that metals levels in the water do not exceed the EPA screening values for recreational, agricultural, or aquatic-life uses.
The Division of Water Quality has analyzed data from samples that were collected below Tibble Fork Reservoir on August 24, 2016. Metals concentrations are very similar to those collected on August 23, 2016.
None of the metals data exceed Utah’s water quality standards. The turbidity in the river appears to have improved, but the sediment in the water measured on Wednesday continued to exceed Utah’s narrative and numeric water quality standards.

August 24-September 1, 2016 – More sampling by DWQ finds that the water exceeds EPA freshwater sediment screening values for aquatic life (arsenic, cadmium, lead, and zinc). Public cautioned by DEQ to avoid sediments.

August 26, 2016 – Cedar Hills staff shuts off the weir to pond ten (2:31 PM) as a precaution, in order to prevent American Fork Canyon river water from entering the Cedar Hills pressurized irrigation system. Water is still flowing through Cedar Hills in the Pleasant Grove Irrigation ditch, which is not under the control of Cedar Hills.

September 2, 2016 – Weir to pond 10 reopened by Pleasant Grove Irrigation staff, after consulting with Cedar Hills staff. The water appears clean enough to enter the Cedar Hills irrigation system. During this time, DWQ continues to test water and sediment samples.

March 23-24, 2017 – Even though DWQ had continually asserted that the results of the samples they took do not exceed human health screening values for recreational exposure, as an added precaution Cedar Hills takes soil, sediment, and water samples from the following locations:

Water sample at pond 10 weir at the golf course. This is the source of PG Irrigation water entering into Cedar Hills and comes directly from American Fork Canyon.
Sediment sample at pond 10 near water inlet. This is the first point of settling for sediment and any heavy metals contained in the water. If there was an issue, this is where the highest level of contamination would occur.
Water sample at pond 12. This is the second point of settling and the point where water is sent to the Cedar Hills pressurized irrigation tank for residential use. If water samples from this location show no concerns, then all irrigation water for the rest of the pressurized irrigation system would also be approved for irrigation use.
Soil sample at Mesquite Park. This sample was taken at the low point where water would collect and be concentrated and is one of the first public areas coming out of the upper pressurized irrigation tank.
Water sample at Heritage Park diversion dam. This sample tested Pleasant Grove Irrigation water in a popular recreation area.
Sediment at Heritage Park near Amphitheatre. This sample tested Pleasant Grove Irrigation creek bed sediment in an area of high recreational use.
Sediment sample from the ditch near pond 10. This is an initial point of entry where water and sediment enters from American Fork Canyon.

The results of these tests were presented during the May 2, 2017, City Council meeting, with a representative from the Department of Environmental Quality discussing the findings. Results showed that the total metal concentrations in the water, soil, and sediment samples were below the recommended values for recreational and irrigation use. Based on this information, as well as test results on other samples provided by American Fork City and DEQ, it was determined that the soil, sediment, and irrigation water throughout the city is safe to use for irrigation and recreation.

It is important to note that there is no location within the city that receives only American Fork Canyon water for irrigation purposes. Water that enters the PI tanks for irrigation use also includes water from Central Utah Project and culinary water, in order to meet demand throughout the city. Another concern that was raised is the possible dredging of sediment in the pressurized irrigation ponds on the golf course. The city has never and will never dredge sediment from those ponds, as it would destroy the lining of the ponds.

Any questions may be directed to the city manager or the mayor and city council.