Protecting Local Water Sources With Stormwater Management

 

While Utah is widely perceived to be a desert state and is statistically the second driest in the nation, during mid to late summer, air masses filled with moisture from the Gulf of California or Gulf of Mexico periodically enter the state. These air masses frequently cause cloudbursts and flash flooding. These high intensity, localized rain events combined with the steep topography creates challengers such as excessive water runoff. 

To prepare for any major rain events, Kennecott has designed its stormwater management system to handle a 100-year, 24-hour event. 

 

Why is Kennecott concerned about stormwater?

Kennecott is committed to minimizing the impacts we have on our community. Stormwater can potentially carry pollutants into local water sources. That’s why construction projects and industrial operations are required to have stormwater management plans and NPDES (National Pollutant Discharge Elimination System) permits. 

Over the past three years, Kennecott has improved existing and added new stormwater basins to increase capacity and mitigate runoff when large rain events occur. The new system was designed and constructed well beyond regulatory requirements. 

Regulatory requirement Kennecott's design
25-year, 24-hour event 100 year, 24-hour event
Release of deleterious materials Gravity flow
Dam safety considerations

Account for sediment

Drain in 24 hours

 

A look at Kennecott’s new stormwater basins

In September 2013, a major rainfall event overflowed drainage basins at the south end of the Bingham Canyon Mine. At the same time, Kennecott was developing plans for new mining operations in the south and east sides of the mine, which would require updates to the stormwater management system. In 2013 and 2015, the Utah Division of Water Quality granted Kennecott permit modifications allowing the company to upgrade its water collection system. 

The new system increased stormwater basin capacity from a 25-year, 24-hour event to a 100-year, 24-hour event.

The new system also has the ability to handle surface water separately from subsurface water. These two types of water, surface and subsurface, have different levels of quality, so it’s safer, cleaner and more efficient to handle each separately. Surface water from storm events is directed to the stormwater basins while subsurface water is directed to a different collection system. Ultimately, both types of water are either piped to the Bingham Canyon Reservoir system or treated and reused in Kennecott’s operations.

One of the most interesting features of the Alternative View project and new water collection system is that it enables reclamation of mining-impacted land. The soil cover and placement of overburden rock (un-economic material from the mining process) are designed to reduce runoff and erosion. Additionally, the basin areas are progressively re-vegetated with native plants. The result is a more natural looking landscape.

The new stormwater management system is regularly maintained and inspected. Groundwater is regularly tested from a network of groundwater wells located near the stormwater and groundwater collection systems to ensure the systems are working as designed.

A map showing the stormwater basin locations

One of the stormwater basins

Sources: 

https://weather.com/news/climate/news/extreme-rainfall-precipitation-recorded-50-states

https://www.epa.gov/npdes/npdes-stormwater-program