As you probably know, during a site investigation the United States Environmental Protection Agency (USEPA) inadvertently breached loose rocks that had been holding back drainage at the abandoned Gold King Mine near Silverton, Colorado. As a result of the spill, more than 3 million gallons of acidic mine drainage containing metals such as manganese, zinc, copper and lead were released into Cement Creek, a tributary of the Animas River which eventually flows into the Colorado River. The location of the Gold King Mine spill is about 850 miles upstream from the Colorado River Aqueduct intake at Lake Havasu.
The San Diego County Water Authority does not expect any adverse impacts to our water supply as a result of the Colorado mine spill and has provided the following information to allay those concerns:
- Lake Powell and Lake Mead will provide significant protection between the spill and the Metropolitan Water Districts’ (MWD) Colorado River Aqueduct intake at Lake Havasu. It is anticipated that water quality constituents present in the mine discharge would be at background or non-detectable levels by the time supplies reach Metropolitan’s intake several years from now.
- There is approximately 850 miles of river/reservoir area between the spill and the intake to the MWD system
- In addition, the Colorado River Aqueduct is approximately 242 miles long
- There are tens of billions of gallons in storage and along the various rivers that will serve to dilute the spill prior to reaching San Diego County
- There will be long detention times associated with Lake Mead and Lake Powell
- It could take several years before any of the spill water reached our system, if at all, due to the large amount of water and distance between the spill and our service area
- Water quality constituent levels are expected to be at normal levels prior to reaching the intake at Lake Havasu
- USEPA, state and federal agencies, as well as numerous downstream water utilities will sample, report constituent levels and monitor the impacts to source water well in advance of any of that water reaching our service area
- This is likely to be one of the most monitored spill response efforts in memory
- There are numerous treatment and operational responses that can be taken to respond to, and mitigate, any potential risk to our water supply.
- The San Diego County Water Authority will continue to monitor response efforts as well as continue to sample our water for metals and other potentially harmful constituents (they sample our water quality within the aqueduct in real-time at several locations, pull grab samples on a weekly basis, and conduct additional reservoir water quality sampling monthly). They also receive water quality reports directly from Metropolitan Water District and monitor flows 24/7 thru their Escondido Operations Center.
- USEPA is containing and treating ongoing drainage from the mine site. USEPA also is conducting ongoing monitoring, both through water quality sampling and visual observations, and continuing to coordinate with all affected parties, including water users. Water quality data reports and updated response activity information is published on-line at epaosc.org/GoldKingMine.
- Metropolitan will continue to regularly monitor its source water supplies for metals and other potentially harmful constituents. We also are coordinating with our upstream Colorado River partners to assess any impacts of this event.