CRITERIA

Recommended Criteria for Booker Creek Watershed Studies

               Booker Creek Watershed Alliance, August 8, 2014

The Booker Creek Watershed Alliance joins concerned Town staff in advocating for a watershed-wide and comprehensive approach to riparian and stormwater management. It is the only effective method to address the damaging effects of stormwater runoff so clearly evident, and continuing. Inadequate piecemeal, and reactive site – specific stormwater management, though necessary and well-intentioned, has resulted in episodic damage to businesses, residences, and waterways throughout the Town. Especially in anticipation of continued development pressures in the watershed, we must upgrade our efforts and strategies to protect our remaining resources.

The Alliance stakeholders support and recommend the development of a watershed plan that will:

  • Measure, or estimate, major sources of excessive stormwater discharge and erosion/sediment load into the watershed for current conditions and likely future build-out scenarios.
  • Catalog properties, structures, and natural resources presently degraded or threatened by current and future flooding, erosion and sediment deposition.
  • Catalog local, state and federal resources available to address stormwater problems in the watershed.
  • Identify specific solutions, including policies, practices and projects, to address present and potential future flooding, erosion, sedimentation, water quality, and other stormwater problems in the Booker Creek Watershed.

 

Our recommendations include:

  1. Determine stream flow volumes. Measure stream flows in all major tributaries in the Booker Creek Watershed.

Comment: It is important to measure watershed flows at key locations above lakes and major structures, near the headwaters, at sub-watershed outlets, as well as at points in between where large amounts of water enter into streams.

  1. Determine sediment loads. Identify sources of overland and streambank sediment loads and erosion into Booker Creek and tributaries. Measure or estimate sediment transport at locations including: a representative site in the headwaters, Lake Ellen inlets, riparian banks between Lake Ellen and Eastwood Lake, and at the confluence of Bolin and Booker Creeks.

Comment: It would be important to characterize sources and estimate sediment loads for each sub-watershed, including assessments of stream stability where appropriate.

  1. Catalog existing stormwater structures. Identify all existing stormwater detention and treatment structures within the watershed. Assess each structure for functionality. In addition, review maintenance history, identify responsible parties/owners, and determine maintenance needs for an on-going program.
  1. Assess water quality.

(a) Identify pollution sources and list key pollutants to the watershed.

(b) Consider how Jordan Lake buffer rules may eventually require control for phosphorus and nitrogen for existing development.

(c) Investigate the status of the remediation of UNC superfund and landfill sites and their impact on ground water, and toxicology.

Comment: Note the 2003 Little Creek Watershed study that showed elevated levels of abnormal aquatic organisms below Lake Ellen.

  1. Calculate future flood conditions. Form a partnership with FEMA and the State to develop future conditions flood-plain maps. Study projected increases in impervious surfaces by using existing planning data which includes anticipated future development.

Comment: Mapping based on updated data for future conditions will yield essential information about various development scenarios, flood plain changes, altered stream discharge, additional stream buffers, or measures needed to prevent roadway flooding which can cause accidents and damage to property. (See simple tool: the EPA SW modeling site, http://www2.epa.gov/water-research/storm-water-management-model-swmm.) Raleigh, Greensboro, and Mecklenburg County, all successfully use future conditions flood plain mapping to manage development.

  1. Improve water storage. Provide recommendations to reduce frequency of flooding and peak flows of water going into creeks and lakes so they have a chance to maintain and restore themselves.

Comment: Recommend potential sites for storage and a maintenance budget in order to address flooding hazards and to protect property owners downstream, including areas that have suffered some of the greatest damage.

  1. Evaluate and recommend regulations.

Given changing climate conditions bringing many more large storms, review Town regulations and make recommendations for how to accommodate them with an eye to designing standards that address Chapel Hill’s specific local conditions.

Comments:

(a) An evaluation may show that our stormwater volume standard should be much higher than our local two-year frequency, 24-hour storm-duration event.

(b) Review and consider recommending changes of the standard that stipulates the rate of runoff not exceed the pre-development runoff from the 1, 2, and 25 year 24-hour duration storm events and evaluate how this standard is enforced.

(c) Consider a policy whereby new development keeps most runoff on-site via swales, rain gardens, and catching stormwater in cisterns for landscape watering use. (Some periodic high flows are ecologically desirable.)

(d) Recommend how to prepare for the Jordan Lake standards for existing development to be effective in a few years.

(e) Consider reinstituting single lot erosion control requirements. (These were eliminated in 2012 by the Town Council and replaced with performance standards.)

  1. Ensure that the watershed study encompasses a study of stream channel conditions over time, including stream stability assessments. 

Comment: This information will yield the most accurate information about where to build new stormwater facilities. This 2014 watershed study results should provide a baseline that is revisited periodically, say every 5 years.

  1. Monitoring. To ensure an effective stormwater program, we recommend a monitoring program for stream flow, pollutants, sediment, and macro invertebrates.

Comment: This monitoring would establish a sound estimate of baseline water quality and stream channel condition for use in future studies. We need to continually monitor the effectiveness of our control and preventive measures.

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