Ottawa River Watershed Sediment Control Demonstration Project
Ottawa River Coalition
Basin Program Funds:
There is excessive sediment coming from the urban areas in the Ottawa River watershed. There is a need in the 372 square mile watershed for a sound and highly visible demonstration and study site of well designed and functional sediment basin located in an urban setting.
Siltation in the Ottawa River is identified as the leading cause of organic enrichment and low dissolved oxygen levels in water runoff. The river segment adjacent to the proposed demonstration site for this project is currently in non-attainment for the warm water habitat use designation.
To date, the Ottawa River Coalition has only found one detention/retention/sediment basin in the entire watershed that appears to be functioning properly. The vast majority of such basins are merely serving as an extension of the channel. Most have outlets and inlets designed to the maximum allowable size, therefore short-circuiting the process. The size, shape and depth are often dictated by the marginal space made available and outlets are commonly oversized and placed too low. Maintenance practices generally involve mowing the monoculture plant system much too low. Despite their recognition of accelerated runoff and downstream flooding issues, our drainage professionals have yet to truly embrace the necessary and practical function of a sediment basin. Local engineers, contractors and agency personnel keep abreast of current stormwater technology through publications, conferences, web sites, and vendor communications, but they have yet to make the connection with water quality. A long term demonstration training sight would enhance the training of local contractors and improve the water quality effectiveness of retention sediment basins in the watershed.
The location of this 37 acre demonstration site is in the Lima, Ohio city limits on land owned and operated by the Lima City School District. The site is the new Lima Senior High School complex immediately adjacent to the Ottawa River. This project modified a poorly engineered detention basin on the 37 acre site to function as a sediment basin by increasing the bottom or treatment area, raising the outlet, and establishing a diverse planting of wetland plants for the purpose of reducing the volume of sediment leaving the basin. This included monitoring the effect of sediment reduction by collecting and analyzing water discharge samples from three storm events.
A deflective separation stormwater treatment unit (in-line manhole type) was installed to intercept runoff from approx. a .6 acre area of parking lot. This included evaluating and quantifying the materials removed from the continuous deflective separation stormwater treatment unit during cleaning events. Five island catchment areas were modified by installing french drains and raising the outlet height or lowering the catchment depth as a means of capturing the first flush from parking lots, providing for detention, and enhancing infiltration. A field day event was conducted four hours in length, showcasing this stormwater treatment and sediment removal demonstration and study site, targeting contracting, development, and agency people involved in the design, regulation/permit/approval, and installation processes.
Construction on the modified basin was completed by April, 2004 and included: installation of a concrete flume between basin inlet and outlet and subsurface drainage in the bottom perimeter of basin; completion of excavation (raising outlet) and shaping in basin bottom; installation of rock chute or deflector at the basin inlet and importing Lima Soil product as topsoil enhancement; and preparation of the seed bed, plantings and installation of erosion control fabric in places to protect critical areas. Analysis indicates, from inlet to outlet, sediment loads are reduced by 65%. Chemical Oxygen Demand is reduced by as much as 50%. As watershed continues to stabilize, post-construction, sediment loads are expected to decline. The basin is effectively conveying, trapping and holding runoff events. The high school is utilizing the area as a land lab. Since the fall 2004, students (over 250 volunteer hours) have conducted maintenance and exploration activities and installed birdhouses. The school has cooperated with a hands-off approach in regard to mowing and other landscape management.
A Stormceptor STC 450i unit was installed as an inline device to remove total suspended solids and free oil from stormwater runoff. It also serves as secondary treatment to one of the parking area islands. In late spring 2005, the City removed 600 pounds of accumulated sediment and water deposited since its Fall 2003 installation. No laboratory analysis was made, as the objective was to prepare for quarterly analysis in a more stable, post-construction environment.
Five parking lot "islands" were modified to function as filters. Concrete curbs were reduced so that water could sheet drain in. Excavation created a dish effect. Catch basins were connected with perforated tile, set into a beds of stone. The stone columns were wrapped in landscape fabric. Final excavation and shaping of the areas left the catch basin tops exposed to allow first flush or small runoff events to reside and filter. In the absence of curbs, Presto Geoblock porous pavement material was installed to provide vehicle load support.
On 10/15/04 approx. 58 people attended the project field day. It rained all day, limiting plans to place different project partners out at the specific practices and speak with circulating attendees. Instead the slide presentation was expanded to more thoroughly cover the different practices. The school provided use of their auditorium for the presentation, which was repeated 4 times. Displays were set up for attendees and school student class members displayed project boards explaining student work on the project.
Contact: Ms. Beth Seibert, 419-223-0040 ex107