Planners get lessons on stormwater management
The Morgan County Planning Commission heard and viewed slide presentations from Region 9 Chesapeake Bay Coordinator Matthew Pennington and from Arro Consulting Engineer Richard Parks on voluntary best management practices for stormwater management.
The best management practices are recommended by West Virginia’s Chesapeake Bay Watershed Implementation Plan, or WIP, and are now voluntary, but are scheduled to be mandated in 2015.
The Planning Commission is in the process of determining how the county’s stormwater management ordinance should be modified to bring it into compliance with the WIP.
The county received a $10,000 Chesapeake Bay Regulatory and Accountability grant to study how the Bay initiative will affect the stormwater management ordinance and has commissioned Parks to generate a report detailing how the ordinance may be modified to bring it into compliance.
The presentations took place at the June 26 commission meeting and were part of the education planners need in order to understand the issues involved.
Quantifying runoff
The first presentation given by Pennington was titled Stormwater Management 101.
It detailed how stormwater runoff can be quantified using a spreadsheet, graph and calculations based on weather conditions, the square feet of an area, type of soil or surface and the travel time to the lowest point where discharge into the watershed occurs.
The Chesapeake Bay requirement is to capture the first 1 inch of stormwater runoff during what is defined as a two year storm dropping approximately 2.75 inches of rain.
Depending on the permeability of the area of soil or area of surface such as a roof or parking lot, numbers can be determined and assigned to calculate the amount of water that infiltrates the ground or surface and the amount of water that runs off.
From those figures, the amount of runoff that needs to be captured by stormwater ponds or other water retention devices and structures can be calculated.
If this all sounds a bit cerebral, it is. The purpose is to give engineers designing new developments tools to determine what stormwater management practices need to be implemented in order to be in compliance with the WIP.
Cost of compliance
Parks followed Pennington’s presentation with his own detailing how recent examples of development projects could be modified to bring them into compliance, and at what cost.
His first example was a shopping center with 80 percent impervious surfaces.
Some ways he said to capture rainwater were the use of underground retention structures, fire retention ponds, islands of green space with grass and shrubs to caption water and filter out nutrients and porous pavement for infiltration into the ground.
Other examples were projects with more land available for green space where retention basins with vegetation can be constructed in low lying areas to create what are called bioswales.
Bioswales are swales with specific vegetation planted designed to soak up water and nutrients from runoff.
Although Parks said he will not have the report completed until sometime in August, preliminary findings are that developers should focus on environmental site design early on in the design process and the design should minimize impervious surfaces and use infiltration wherever possible.
Parks estimates the extra cost to developers to implement both quality and quantity control of stormwater runoff on a project could run anywhere from zero to 20% of the cost of the project.
He cautioned if a developer doesn’t implement good stormwater management practices, the cost to retro-fit after 2015 will be even higher.
