Conservation

Nutrient levels in Jordan Lake

March 2006

The OCG Program Meeting on January 11 presented two speakers who addressed the problem of excess nutrients in Jordan Lake and the measures planned to reduce them. The first speaker, Ed Holland, Planning Director for OWASA (Orange Water and Sewer Board), talked about the Jordan Lake Management plan and the actions that OWASA has taken in the past and will be taking in the future to improve water quality. The talk included a general description of the watershed and a discussion of the management plan developed to reduce nutrients loads, especially nitrogen and phosphorous.

The starting place for a plan to reduce pollution is an understanding of its sources, and Holland presented graphs showing sources of non-point pollution (not coming from a specific place such as a water treatment plant). According to Tetra Tech, the company that has provided many models of Jordan Lake’s nutrients for the Division of Environment and Natural Resources, 68% of the nitrogen and 84% of the phosphorus come from nonpoint sources. Of the nonpoint source nitrogen, 36% is from agriculture, 29% from residences, 9% from commercial and industrial sources, and 19% from forests. Of the nonpoint sources of phosphorus, 51% comes from agriculture, 12% from residences, 6% from commercial and industrial sources, and15% from forests. Holland also presented Tetra Tech’s projection of the effects of specific reductions in nitrogen and phosphorus.

OWASA, which has concerns about the future based on projected growth, has plans to reduce point source nutrient concentrations, including the construction of expanded treatment facilities.

According to the second speaker, Alan E. Rimers, who is on the Stormwater Advisory Board, one of the important ways to reduce the unwanted substances draining into the lake (toxics as well as nutrients) is to slow and reduce runoff from impervious surfaces. Among the ways to do so are riparian buffers for streams, swales by the sides of roads that can collect runoff and allow it to be absorbed by the soil, constructed wetlands, sand filters, and green roofs. Chapel Hill has ordinances in place for construction of some of these structures but faces challenges in this area because it is already over 85% developed.

Discussion followed in response to questions from the audience on the difference between political boundaries and topography and the natural flow of water in a watershed, sources of residential nutrients, and other matters.

— Report by Judith Ferster and May Becker

January 2006

In response to the impairment of the Jordan Lake, in January the state Environmental Management Commission will circulate a draft of new rules to control nutrients that will affect both Orange and Chatham Counties. With a series of meetings focused on the lake, the OCG will help members prepare to respond to the draft in public hearings before the new rules are finalized and implemented. One of those meetings will be a joint meeting of the OCG and the Carolina Meadows Birdwatchers at Carolina Meadows on Sunday March 12 at 7:30. The main speaker will be Professor Norman Budnitz of Duke University, speaking on the birds of Jordan Lake.

—Report by Judith Ferster

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