Statement to Carrboro Aldermen about stormwater ordinances

June 26, 2012

Dear Mayor and Members of the Board of Aldermen:

Friends of Bolin Creek is very pleased Carrboro is considering storm water ordinance changes on June 26th that will further protect Bolin and Morgan Creeks and their tributaries. We support the Town in proceeding with the Local Stormwater Program required under the Jordan New Development Stormwater Rule to reduce nitrogen and phosphorus from stormwater runoff.

Likewise, we congratulate and support the Town in taking a good first step to address a crucial stream protection component of stormwater management with the proposed Stormwater Volume Control Ordinance. At a February Symposium ,”Can We Heal Our Local Waterways?”, local watershed professionals identified volume controls as a needed part of local stormwater ordinances. All those presentation are available online at our website

There is good evidence that volume controls are necessary and effective at protecting streams. Controlling peak flow and pollutants are not enough. The amount of impervious surface dramatically increases with development in a watershed. This results in greater volumes of stormwater entering streams which impact water quality and leads to “Urban Stream Syndrome.” Commercial development increases this effect. If we ignore the total volume of stormwater in our storm water management plans, we are left with a loss of biological integrity, low stream flows between storms and depleted groundwater stores.

This stormwater volume ordinance addresses a problematic gap. We do not currently control the total volume of stormwater runoff entering our streams. Currently, we have an ordinance that addresses peak flows, and with adoption of the Jordan Lake rules, we will also have an ordinance to reduce nutrient pollution. However, because the Jordan Lake rules allow developers to make payments in lieu of compliance, they will often not protect our local streams as originally intended. In this instance, the proposed volume control ordinance will provide further protection of our streams.

We must recognize that the perfect is the enemy of the good. From our discussions, we unanimously came to this conclusion: This ordinance is a first good step and we urge the Board to approve the regulations as written. Many projects coming forward for possible future approval can be improved by this ordinance.

In light of the many good questions that have been raised about this ordinance, as well as the tremendous local resources on the subject, we further recommend that the Board establish an action item to revisit all stormwater ordinances in one year. As a part of this review, we ask that local experts meet with your Environmental Affairs Board in an open process to evaluate the effectiveness of the current ordinances, address concerns, and discuss potential improvements.

The time to act is now. Despite the imperfections of this ordinance, it is moving in the right direction. This ordinance will promote a healthier environment for our town, including better stewardship of Bolin Creek.

Friends of Bolin Creek

Note:  Friends of Bolin Creek has asked members of our Technical Committee, Michael Paul, Rob Crook, Dickson Phillips and Betsy Kempter to review the proposed ordinances. They make the following observations, some of which are similar to the comments made by your Planning Board.

  • The means of measuring runoff (presumably Jordan Lake accounting tool) and means of reduction (presumably state accepted BMPs listed by Jordan Lake accounting tool) are not specified by the ordinance. Likewise, the percentage should be stated as it will be used: 50% increase (from current site pre-project values) on land that has been previously developed, up to 200% (from current site pre-project values) for undeveloped land. Otherwise, this will provide disincentive for appropriate action.
  • While piedmont soils, and those of Carrboro in particular, can present a challenge for infiltration and runoff reduction, they certainly are better than pavement, and with skilled management have both good infiltrative capacity and soil nutrient retention capacity. While these volume levels are a good first step, we need to work for greater reductions in line with the best in the nation to protect our environment and exemplify Carrboro’s progressive ideal.
  • In addition to the state approved BMP list, demonstrable methods for reducing runoff and improving infiltration should be allowable and credited by the ordinance if scientific evidence of success of these methods can be provided. Given the lack of total success with current state methods, this would encourage developers to consider more creative and proactive solutions to runoff.
  • The Jordan Lake tool may be the best currently available tool to use in approximating runoff, but it does not take into account local soil variability or topography of the land, both of which profoundly affect runoff and the means by which it can be remedied. It will be worth exploring or developing other methods for improved future use.
  • The use of a percent rather than reference to specific flows assumes channels respond linearly with size – and this is not the case. It varies with size. So, 200% of runoff for a small stream with a relatively large drainage represents a very different flow shift than in a large stream with a small drainage area.
  • A stronger statement would include that Carrboro seeks to adhere to a LID strategy in new development that will include the use of bioretention, rain gardens, rain barrels, cisterns, detention basins, curb cutouts, treating water close to the source (i.e. get rainwater into the ground as quickly as possible), disconnect downspouts and begin stormwater management planning early in the site planning phase. LID is cheaper than conventional stormwater conveyance systems (

Signed Friends of Bolin Creek

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