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Wet Weather Initiative

Meeting Minutes

Present: 

• Holly Utrata-Halcomb, Chair
• Chris Calpin, Camp Dresser & McKee
• Gary Van Horn, HC Public Works
• Cory Chadwick, HCDOES
• Nancy Ellwood, MCWC
• Jim Rozelle, FMSM
• Karen Ball, HC Commission (Portune)
• Patrick Karney, MSD
• John Hunter, LWVCA&MCRP
• Robert Jansen, Mill Creek Conservancy District
• Jeff Leedy, HC Public Works
• Dave Sparke, Anderson Twp (HC Twp Rd. Supervisors)
• Sam George, City of Cincinnati SMU/MSD
• Ed Webber, HC Public Works
• Wesley Wimmer, SMU/MSD
• Jason Hammer, HCGHD

PRESENTATION ON STORMWATER MANAGEMENT - Chris Calpin, Camp, Dresser & McKee

Mr. Calpin reviewed a highly successful stormwater management approach adopted by the Dublin, Ohio in response to citizen concerns for the increasing impact of stormwater events on streambank degradation and flooding. City leaders were concerned that anticipated developments in their watershed would cause major stormwater problems.
Mr. Calpin's talk addressed four areas related to the Dublin stormwater management plan:

• Increased frequency of large events
• Increased frequency of overbank flow
• Stormwater pre- and post development calculations
• Appropriate runoff calculation methodology
  -Rational Method

Development increases imperviousness and impacts watershed hydrology and hydraulics and alters the time/runoff volume profile of stormwater. In addition, over the last thirty years the volume of rainfall in 1% probability events has increased by 20 %. Smaller events are not being controlled by retention policies leading to more frequent overbank flooding and stream bank erosion. Measured rainfall volumes are required for accurate modeling of local pre-development runoff for use in designing post-development retention systems. Downstream flooding can be aggravated by the cumulative impacts of retention policies applied throughout the watershed.

The Dublin stormwater program has been effective in addressing these problems. Components of the program were:

• A stormwater master plan based on databased modeling.
• Stormwater funding evaluation
• Administrative policies and stormwater ordinances comprehensively addressing water quality, flood control and aesthetics.
• Evaluation of BMPs and master plan impacts.

Several key features were identified in the Dublin experience.

• Pre-development runoff volumes were based on a calibrated SWMM model. The release rates tended to be lower for small events than those generated by the Graphical Peak Discharge Model and were incorporated into the stormwater ordinance. For example the SWMM runoff predicted for 10% to 100% probability events averaged 0.124 inches vs 2.54 % by the Graphical Model. 4%, 2%, and 1% events tended to be closer by either model.
• Dublin's ordinance dictates allowable post development runoff release rates and the ratio of pre/post development release rates and controls.
• The Dublin approach has helped to control erosion and flooding while promoting attractive aesthetics that have enhanced the value of developed properties. Maintenance responsibilities are shared and spelled out. Cost to developers is minimally increased and more than compensated for by avoidance of post-development complaints from homeowners.

Without the calibrated SWMM model developers were over-predicting pre-development runoff for the smaller storms, thus exacerbating stream bank erosion. SWMM provided built in safety margins for retention. Differences between SWMM and TR55:
 

SWMM

• Impervious area

• Directly connected Imp. Area
 

• Pervious Area

Overall, the difference is in databased calibration vs. tables and the impact of the difference is primarily in increased retention for small rain events.

Dublin continues to refine their program. In the future they plan to better control volume-time release profiles over a critical 10 to 18 hour post event time period for better erosion and flooding control in downstream corridors.


WET WEATHER INITIATIVE LONG RANGE PLANS
The Mission Statement and Goals of the Wet weather Initiative were discussed and revised:

Mission Statement:

"To promote effective management of stormwater in Hamilton County to prevent pollution of streams, rivers and lakes and to reduce flood damage of structures, streambanks and riparian corridors."

Goals:

Planning:
1. Support the development of a plan for countywide stormwater management.
2. Recommend (del. Support) the utilization of environmental and hydrological expertise by the County's Regional Planning Department.
3. Study the impacts of land use practices and promote the protection of riparian areas.

Data Collection:
1. Encourage the development of a readily accessible centralized system for collecting stream quality data.

Education:
1. Develop a system to provide stormwater information to the public: tie into HCSWCD website and link to Public Works Stormwater Division. Put stormwater data and WWI minutes on the website with the most hits and link all the others.
2. Develop a stormwater video for distribution to schools (add and public access television) in the county.
3. (Add a watershed signage goal - to be drafted by signage committee)

Action:
1. Support (insert and provide) the development of (insert accurate models to integrate more) effective County Stormwater Regulations.
2. Support amendment of ORC 6117to permit better enforcement of stormwater regulations.
3. Explore the need for an Environmental Court or Magistrate to handle all environmental cases within the County.
4. (Add a watershed signage action goal)

SELECTION OF A NEW WWI CHAIRPERSON
WWI Chairperson, Holly Utrata-Halcomb, has announced her intent o step down as Chair at the end of the year and has asked the committee to elect a replacement. Dave Sparks pleaded a conflict with new responsibilities and urged support for Jeff Leedy of Hamilton County Public Works as the new Chair of the WWI. Meeting attendees pointed out the primacy of HC Public works in County stormwater management and urged Mr. Leedy to accept. He agreed to review his responsibilities with his management and give an answer at the next meeting.

NEXT MEETING
The next meeting of the WWI committee will be at 9:30 AM at DOES, 250 Wm. Howard Taft, on Thursday, November 29, 2001.

Mr. Caplin’s Power Point Presentation will be posted on the Hamilton County Soil & Water Conservation District Web Site www.hcswcd.org Scroll down to Programs and Services and hit Wet Weather Initiative.