TITLE: Title
Tom’s Creek Neighborhood Walk-About Update
PURPOSE: The purpose of this agenda item is for the Board of Aldermen to receive a report from staff on the recent walking tour and visits with property owners in the Plantation Acres neighborhood
body
DEPARTMENT: Planning, Public Works
CONTACT INFORMATION: J.D. Freeman - 919-918-7427- jfreeman@townofcarrboro.org <mailto:jfreeman@townofcarrboro.org>; Patricia McGuire-- 919-918-7327 - pmcguire@townofcarrboro.org <mailto:pmcguire@townofcarrboro.org>
INFORMATION: In response to the significant rain event on August 2, 2016, members of Town staff and the Board of Alderman participated in a walking tour of affected properties on Saturday, August 27, 2016. Twenty-eight properties were included in the tour, the Aldermen and staff divided into four groups and each group visited seven properties. The list of properties, neighborhood map, and interview form used to collect information from each property owner is included as Attachment B. A summary of information compiled from the interviews, including those carried out in 2013, is provided as Attachment C. A presentation with photos and other information provided will be made at the meeting Tuesday night.
Stormwater management in Town is an ongoing focus of attention and activity. The Town has been actively evaluating the stormwater conditions and concerns in the Tom’s Creek area this year: a hydrologic study of the area was presented on May 17, neighbors were invited to submit flooding information, which has been incorporated into a dataset and map, active monitoring and clearing of the major street culverts in anticipation of rain events occurred, and the August 27 walk was held to visit the properties directly and find out more about specific experiences. A copy of the hydrologic study and minutes of the Board of Aldermen meeting are included as Attachments C and D. The August 27 interviews provided information about factors to consider in assessing the existing situation and follow-up actions. Unless indicated otherwise, a brief summary of actions and results to date is provided below this list.
• Assessment of functionality of Lloyd Square neighborhood stormwater management system.
• Assessment of the stormwater in the vicinity of an elevated sewer pipe on Quail Roost Drive and functioning of the system installed in relation to paving and sidewalks on this street and James Street. A letter from Sungate Design Group providing this information is in preparation and will be distributed when it is available.
• Condition/need for replacement of a culvert that allows driving access to the Duke Energy overhead powerlines in an easement near Rainbow Drive. Staff has been working to communicate with Duke Energy representatives about this situation.
• Proposed stormwater management system for Lloyd Farm and how it will affect existing properties and flooding conditions. An evaluation of this is underway and information will be provided at the continued public hearing on the conditional rezoning on October 5.
During the neighborhood walk on August 27, several property owners commented on the stormwater system for the Lloyd Square Architecturally Integrated Subdivision. Comments noted that the pond was not working properly, that most of the homes were not allowed to connect to the pond, and that the engineering was incorrect. Photos and videos of Tom’s Creek downstream of the pond were shared with Board members and staff and property owners commented on the number of times storm events in the current year had resulted in flooding conditions. Following the walk, staff investigated the current condition of the pond, and the process by which it had been approved to verify its intended functioning. The Lloyd Square stormwater management system is designed to address the stormwater impacts of the construction of 15 dwelling units on a previously undeveloped 5.98 acre wooded parcel. For design purposes the site has been divided into two portions separated by a drainage swale, consistent with the pre-development topography and drainage to two separate unnamed tributaries of Tom’s Creek. The larger northern section contains 3.41 acres and drains to a new dry detention basin which provides detention up to and including the 25 year storm event to below pre-construction runoff levels for the entire site. The new stormwater associated with the impervious surfaces from eleven of the subdivision’s approved 15 lots drain to the dry detention basin. The smaller southern section contains 2.57 acres and drains to an existing unnamed tributary. Due to the oversizing of the detention basin, the first inch of rain resulting from the impervious surfaces associated with the remaining five lots passes through bioretention areas for water quality treatment, but is not required to be detained for the purposes of managing the peak discharge of stormwater from the site.
To satisfy the water quality provisions of the LUO in place at the time of permitting, five individual bio-retention cells have been designed to be located throughout the site; these, in combination, treat the stormwater runoff from all of the developed lots. To date, three of these bioretention cells have been installed and are functioning (two of these have been certified). Of the remaining two cells, one is currently under construction, and the remaining one should begin construction in the fall. The as-built package for the dry detention basin was approved in July of 2014. At that time, the basin’s condition and construction documents revealed that it had been built according to the specifications and found acceptable. Following the August 27 walk, inspections revealed the outlet riser for the dry detention basin had been altered and was therefore not functioning as designed. In particular a water restricting end-cap had come off and the inlet pipe was not sufficiently capped and protected by fabric and gravel. The effect of these conditions was to allow water to flow through the outlet riser relatively unobstructed, except by the diameter of the 4-inch pipe therein. The discharge from the pond without the cap in place is approximately 5.5 times the amount that is designed to be released. Since this discovery and communication with the homeowners’ association representatives, the orifice cap has been reinstalled; staff monitoring of the pond has revealed that the rate of discharge for the pipe is substantially reduced. The remaining maintenance issues will be addressed separately and directly with the homeowner’s association.
Additional activities are underway. Site conditions reported by property owners are being evaluated to determine whether they appear to involve public property or private property. The Town’s practice is to follow-up in either case, with either the Town Engineer or both Public Works staff and the Town Engineer, by visiting the sites to more clearly understand the conditions. Where public property is involved, the Town will determine what action is needed and a plan for carrying out those actions is made. Where private property is involved, the Town will seek to assist with clarifying the problem and identifying who an owner might consult with to develop and implement corrective actions. The Town will also consider reviewing such proposed actions and facilitating meetings between property owners, as applicable. Staff are actively working towards a proposal for establishment of a framework to manage stormwater, including flooding and water quality mitigation.
FISCAL & STAFF IMPACT: Anticipated follow-up planned in FY 2016-2017 falls within current budgets for Planning and Public Works.
RECOMMENDATION:r Staff recommends that the Board of Aldermen consider the information in this update and discuss the plan for moving forward in this neighborhood and Town-wide in relation to stormwater management. A resolution that provides an opportunity for the Board of Aldermen to specify feedback is provided as Attachment A.