In particular, the project hopes to increase the understanding of the extent to which copper runoff from architectural copper ends up in water sources.
Recently, the University of Connecticut issued the project's first report detailing some of the project's tentative results. Most importantly, the data indicate that as the rain runoff travels through the storm system's conveyance structures, the copper is chemically bound to organic matter and various anions. This, along with dilution, causes the copper to become largely inactive, or not "bio-available."
What is copper bio-availability? For most organisms to live, it is necessary for them to have access to a certain amount of copper. Too much copper, however, is toxic to some organisms.
Copper bio-availability refers to the extent that copper in food or water is actually available to an organism. Copper often bonds with other elements and the copper in resulting compounds sometimes becomes unavailable. When this happens the copper is said to be not bio-available. When an organism is able to absorb the copper it finds in food or water, the copper is bio-available.
Some levels exceed guidelinesMany major rivers in Connecticut, which is a densely populated, highly industrial state, have copper levels that exceed Connecticut's Copper Water Quality criteria. The Connecticut DEP is very interested in understanding the sources and effects of the copper on aquatic life.
Studies completed by the Connecticut DEP have shown that elevated copper concentrations from wastewater treatment plants due to the corrosion of household plumbing materials, do not pose a significant threat to aquatic life.
Copper effluent from wastewater treatment plants is strongly bound to organics and inorganics present in the wastewater, which minimizes copper's role in aquatic toxicity.
The Connecticut DEP has turned its attention to other possible sources of copper, in particular runoff from copper roofing and gutters. In order to assist the DEP, the copper industry, through the International Copper Association and the Copper Development Association, has provided funding and technical assistance to the project.
Project objectivesSome of the objectives of the runoff project included the following:
- Track copper in storm water runoff from its sources to the receiving stream and determine the contribution from copper use in architectural applications;
- Develop a mathematical model to simulate the movement and final fate of copper from the time rain falls on a copper roof to the time it reaches the receiving stream; and
- Determine the contribution of various sources of copper to any observed toxicity.
The project is located at the University of Connecticut campus. Only one building on campus contains a large amount of copper architectural material. This building has 11,921 sq. ft. of copper roofing, as well as copper gutters, and decorative flashing.
Currently, 2,583 sq. ft. of the roof is being closely monitored and sampled to determine the copper flux directly off the roof. The campus watershed also contains parking lots, atmospheric deposition collectors, a weir (a small dam which controls water flow), and an air particle filtering station. It also has a well-understood storm water system.
Fifteen rainfall events are sampled each year of the study. During these 15 events, water samples are taken automatically at each of a number of sampling points. This study is designed to show what happens to dissolved copper concentrations and storm water toxicity at each at each point along the storm water system, from the beginning at the copper roof to the end at the system's outlet.
Water samples from a sampling station on a grassy area in a dormitory quadrangle known as "North Campus" show very little copper. Apparently the tiny amount detected comes from wet and dry atmospheric deposition.
Testing at this station shows no toxicity. On the other hand, storm water collected from the campus police station parking area shows a higher copper level that displays toxicity. The extensive copper roof of a large laboratory building sampled at the bottom of a leader in a ground floor laboratory, sheds higher copper levels. As expected, water samples taken from this station display toxicity.
The important finding is that a few hundred yards away, at the outlet of the storm water system, there is absolutely no copper toxicity. In the short distance from the roof through the piping to the outlet, the copper is chemically bound to organic matter and various anions. This mechanism combined with dilution, renders the copper totally inactive - or not bio-available.
(Reprinted with permission from the Copper Development Association.)