TOWN OF CARRBORO STORMWATER ADVISORY COMMISSION

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TOWN OF CARRBORO STORMWATER ADVISORY COMMISSION AGENDA October 11th, 2018; 6:30 pm Town Hall Room 100 Time Item Presenter 6:30 pm Administrative matters Chair Adjustments to agenda

1 TOWN OF CARRBORO STORMWATER ADVISORY COMMISSION AGENDA October 11th, 2018; 6:30 pm Town Hall Room 100 Time Item Presenter 6:30 pm Administrative matters Chair Adjustments to agenda Approval of 9/13 minutes 6:35 pm Capstone Concept Guest, Staff 7:05 pm Tropical Storm Florence Report Staff 7:25 pm Upcoming Meeting Plans Staff 7:40 pm Announcements and Adjourn Chair

2 TOWN OF CARRBORO STORMWATER ADVISORY COMMISSION SUMMARY Meeting on September 20, 2018, 6:30 pm, Town Hall Basement Meeting Room Commission Members Guests Staff John Cox (vice-chair) Tom Hoban Richard Gurlitz Nil Ghosh Jim Joyce Minali Nigam Sarah Vinas Randy Dodd Robert Dickson Jeanette O Connor (chair) Bill Spang Trish Malarkey Kacy Gordon Daniel Perry Heather Holley Randee Haven O Donnell (BoA) Shauna Hay Michael Paul (absent) Cliff Credle Wayne Hadler Mike Humphrey Jerre Kennedy Carol Lerner Andrew Lerner Meredith Bratcher Marek Kossowski Town Engineer Bill Roark Jeff Kleaveland Marty Roupe Administrative Matters The meeting was called to order at 6:32 pm Sanderway CUP Mr. Kleaveland (Zoning Staff) provided a brief presentation with an orientation to the project. Mr. Gurlitz (Sanderway applicant) provided a presentation describing the development application with focuses on: an area overview; stormwater dynamics in the catchment; the CUP process and the information that is required for stormwater documentation at this stage of design; the LUO stormwater requirements and the project s approach to meeting the requirements (general site planning; Filterras for treating 1 water quality event; underground detention for meeting 1-25 year storm event; level spreader for diffuse flow; post construction maintenance requirements. Mr. Ghosh and Mr. Perry presented on behalf of the owners of the neighboring properties located downhill/downstream of the project. They requested that the Commission represent their finding that the materials submitted do not provide sufficient documentation that the submittal satisfies the Town s Stormwater Engineering Review Checklist. This included analysis of: detention requirements; annual volume control/snap tool/curve number calculations; stormwater control measure design and details (e.g., missing calculations for stormwater routing, Filterra sizing, splitter box for level spreader and level spreader sizing, rip rap velocity dissipator); a storm pipe analysis; ephemeral stream calculations at downstream driveway pipe; portions of lots/impervious surfaces draining to stormwater management system. Neighbors of the project also presented information to supplement information they provided prior to the meeting regarding their concerns about the vulnerability of the adjacent properties due to existing flood impacts that have been occurring, echoing the points offered by Mr. Ghosh and Mr. Perry regarding the need for additional documentation, and highlighting that there is no margin for error in the stormwater design, construction, and post construction operation and maintenance. After hearing the above input from the applicant and neighbors and their representatives, the Commission deliberated and prepared review comments that recommended: a re-review of satisfaction of the CUP level Stormwater Engineering Requirements checklist submittal be performed by the Town; and several CUP conditions (drainage of impervious surfaces; peak flow analysis; undisturbed drainage easement for Lot 7) be considered. Lloyd Property Rezoning The SWAC reviewed the rezoning application and recommended that it be affirmed that condition 15 regarding the 50 and 100 year storm events considers the stormwater runoff from the entire site. Adjourn The meeting was adjourned at 11:45 pm. The next meeting will be on October 11th.

3 Stormwater Management in Carrboro A proposed UNC capstone class for spring 2019 September 20, 2018 Overall goals: Improve outreach and awareness of Carrboro s stormwater management program Provide information to Carrboro residents and businesses on how to reduce and mitigate stormwater runoff Conduct a pilot study of stormwater mitigation for a particular area of Carrboro, e.g., downtown, Dry Gulch watershed, and/or another area Advise the Town on specific additional steps the Town could consider to better reduce or mitigate stormwater runoff Preliminary List of Tasks 1. Design outreach and education campaign to raise awareness about stormwater management and mitigation techniques This could include, events such as, a webinar, workshop or a booth at the Farmer s Market as well as online content, newsletters, etc. 2. Prepare content that could include: Best practices in stormwater management o Identify a set of practices suitable for Carrboro o Provide information on relative costs, payback period, and other practical considerations for homeowners, residents, businesses Fact sheets about stormwater mitigation A brief video of particular mitigation projects or sites in Carrboro 3. Consult with a small set of individual landowners who have expressed an interest in reducing stormwater runoff and impacts through practices such as: Reductions in and disconnection of impervious surfaces (green infrastructure), including permeable pavement Rainwater harvesting/reuse Stream buffer restoration Rain gardens Landscaping improvements that increase infiltration, improve soil quality, reduce erosion, and reduce runoff 4. Meet with the Town s Stormwater Advisory Commission to get feedback on the project and to keep it apprised of the Capstone team s work

4 5. Conduct a pilot study on stormwater mitigation Select a particular area or community in Carrboro Meet with residents or business owners Develop strategies for mitigating stormwater based both on available best practices and on interest from stakeholders Estimate the reduction in stormwater runoff and improved environmental quality

5 Tropical Storm Florence in Carrboro In the days leading up to the arrival of Hurricane Florence, the Town provided multiple announcements to help residents prepare for the storm, and preventative maintenance was performed to make sure storm drains were free of obstructions. On Thursday evening, September 13 th, the Town opened an Emergency Operations Center. On Friday, Hurricane Florence made landfall near Wilmington, and then slowed down, turned to the south, then west, then north, resulting in four days of rain Carrboro. The first 3 ½ days saw steady but moderate (1-2 per day) rain compared to what was being received to the east and south. However, the rain gauge at the (recently closed) Horace Williams airport reported about 5 inches on Sunday night/monday morning, including about 3 inches between 5 and 8 am. The saturated soils had no capacity to absorb the rain, resulting in overtopping of some storm drains, and flood conditions for local creeks. The following points and attached pictures offer a brief and preliminary synopsis of selected impacts. 1) The Public Works facility on Smith Level Road next to Morgan Creek experienced the most extensive flooding in recent memory (see attached photos). Specific impacts included: a flood elevation that exceeded the recent flood event elevations; some damage to structures (outbuildings) and equipment; significant stream bank erosion (see photo); and disruption of operations during the storm due to the closure of the driveway and flooding of the yard. 2) Residences along Toms Creek in Plantation Acres have a history of flooding, and experienced it again during Florence- several homes have reported flood impacts. Toms Creek overtopped West Main Street. 3) The property at 103 Phipps Street contains an underground home heating oil tank; a significant amount of the fuel was displaced by water during the storm. The fuel oil ran off across the yard, with some continuing down a roadside ditch, and some crossing the street and into the other roadside ditch as well as the yard at 100 Phipps Street (see attached photos). This situation is regulated by the State Department of Environmental Quality, Division of Waste Management, Underground Storage Tank Section. The homeowner at 100 Phipps Street has entered into a contract with Terraquest to provide remediation (removing contaminated soil), which is occurring the week of October 1 st. Town staff have provided booms and mats to contain any additional oil running off until the remediation is complete, and are also pursuing outreach to encourage residents that may have home heating oil tanks to properly eliminate the risk future spills. More information is available at 4) Some local roads had enough water early Monday morning to require temporary rerouting of traffic. 5) Public Works staff have been repairing erosion around some culverts and storm drains and providing general post storm maintenance.

6 Corner of Phipps and Lorraine looking down Lorraine (100 Phipps Street)

8 Streambank Erosion at Public Works-Public Works fence at top of bank

9 Public Works Driveway Entrance Near Cresting of Flood Waters (mid morning)

TOWN OF CARRBORO STORMWATER ADVISORY COMMISSION

TOWN OF CARRBORO STORMWATER ADVISORY COMMISSION AGENDA November 8th, 2018; 6:30 pm Town Hall Room 100 Time Item Presenter 6:30 pm Administrative matters Chair Adjustments to agenda Approval of 9/20 minutes