As you know, water quality in upper Mineral Creek has greatly improved because of remediation projects near the top of the basin – eight by ARSG, three by Sunnyside Gold Corp/Gold King Mine Corp, and one by the Forest Service. We were planning to ask WQCC to add an aquatic life classification to the creek above Burro Bridge. The fish and macroinvertebrate data clearly show that such a designation is appropriate.
Unfortunately, when an aquatic life classification is added to a stream segment, numeric standards are required for toxic substances such as lead, copper, cadmium, and zinc. (Iron, aluminum, and manganese are not included on the toxic substance list.) Our plan was to use ambient conditions for the numeric standards to protect current water quality. There are several mines upstream of upper Mineral Creek on the list of 48 Bonita Peak Mining District Superfund sites. It’s unknown if more remediation work might be done at those sites, further improving water quality in the future.
The problem is that we don’t have enough data to specify what ambient water quality currently is. EPA took a number of samples over a couple of days in June and a couple of days in late Sept. last year. ARSG took a sample in early Oct. in 2015. The fall samples show pretty good water quality, only zinc and cadmium are little above Table Value Standards (TVS) which are protective of 95% of aquatic life. The June samples are quite high for zinc, cadmium, copper, lead and aluminum. This is the opposite of what we see in Mineral Creek by Silverton where water quality is best in June during runoff and worse in fall and winter.
So we have decided to pull our Mineral Creek proposal until we can collect more water quality data throughout the year to better characterize ambient conditions.
We are still proposing to change the cadmium standard on a number of segments to the new EPA cadmium criteria. Download our proposal here