The Durham City Council has approved another step to building a low dam and new water pump on the Eno River to pump directly into Teer Quarry. This would be the first active pump on the Eno in memory.
Buried under the Durham City Council’s discussions of the coronavirus during their virtual council meetings and work sessions was an item pertaining to the reclassification of a segment of the Eno as a water supply. The City Council approved it without discussion at the April 9 and April 20 meetings.
According to documents filed with the council, the new water pump is proposed for the northwest tip of the quarry and just south of the Eno Trace neighborhood.
“A new water supply intake, located on the Eno River, is necessary to use Teer Quarry as a water supply source,” stated a report by the Durham Department of Water Management.
Actually, Teer Quarry, located at 5090 Denfield Rd., is already a water supply for Durham, but only for emergency use. Lake Michie and Little River are Durham’s primary water supplies.
When asked how much the quarry has been used, Sydney Miller, water resources planning manager with Durham City, said it has just been used once. That was toward the end of the 2007 drought. But as soon as Durham moved to use the quarry by February 2008, the drought let up, making the emergency pump set up unnecessary.
Miller said the proposed new water pump on the Eno would be a “weir,” which is a low dam built across a river.
“The way we intend to make use of Eno River is we would essentially skim water from the river, taking between 10 to 20 percent of the flow, when the flow is high,” he said. “When the river is flooding, we’ll skim some of the water to put into the quarry. So based on historic records, on average, that only occurs 12 days of the year, that we would withdraw water from the river.”
The median flow that city water managers are using to determine when the Eno is flowing “high,” is 49 cubic feet per second.
However, according to the U.S. Geological Survey, the Eno’s median flow for May 9, since 1962, is 56 cubic feet per second.
Durham also has an existing water pump on the Eno, downstream of the proposed weir and new pump, that’s not in use and for emergency only.
“The general concept is… there are some advantages to building some new intake at the Eno River,” Miller said. “If we can do it upstream of the current location, it puts it much closer to the quarry and it puts it at a higher elevation.”
“It allows us to bore a tunnel from the river to the quarry. We would build a weir which would prevent any water from the river flowing into the quarry unless it was flowing high. And we would put in pumps and put in valves. When the river is flowing high, it would allow it to actually flow by gravity into the quarry. And so what this means… is that it would take no power to fill over half of the quarry from the river. When it’s not taking power, it’s much more environmentally sustainable.”
When asked what the need for the project was since Teer Quarry was not even used for the 2007 drought, and has been collecting rainwater during years of record high amounts of rainfall, Miller said, “We will (need it), but we don’t know when.”
“We need to be able to fill the quarry if we’re going to use the quarry. We can use it now,” he said. “Eventually, there will be no water going into the quarry. So we need to be able to put water into the quarry.”
According to the National Centers for Environmental Information, North Carolina’s statewide average annual precipitation was low in 2007, at 34.74 inches. 2018 was the wettest year on record, with 68.4 inches. The state’s wettest consecutive five-year period was 2014-2018, when there was an average of 55.1 inches of rainfall per year. The driest five-year period was 1930–1934, with 44.4 inches.
When asked about the cost of the proposed project, and the capacity of the weir and pump, Miller said they did not know. But to city water managers, the goal is to fill Teer Quarry.
Miller said they did not know how much water is in the quarry currently.
“We want to fill it,” he said.
Miller said Jordan Lake will also be used as a water supply for Durham in the future.
Durham would still need to get approval for the reclassification of the Eno from Orange County, one of the municipalities affected by this change, in order to move ahead with the project.
The Eno River Association did not immediately return a request for comment.
The Durham City Council had already discussed this project at its work session on March 5, 2020, live and in-person. During that work session I answered questions posed by the City Council.
The weir we propose to build would be parallel to the Eno River along the shore. We do not want to dam the Eno River.
The median annual daily flow of the Eno River at the US Geological Survey (USGS) stream gage located at US 15-501 near Durham (USGS 02085070 ENO RIVER NEAR DURHAM, NC) is 47 cfs (cubic feet per second). The flow varies from day to day. On May 9th, had we been operating our proposed intake, we would have withdrawn about 0.9-1.8 cfs of the flow.