FLEET AVENUE GREEN STREET USES VACANT LOT FOR CSO REDUCTION Thomas M. Evans, AECOM Cleveland, Ohio INTRODUCTION As part of the Northeast Ohio Regional Sewer District s (Sewer District) Green Infrastructure (GI) program, the District is required to capture wet weather flows to reduce the volume of Combined Sewer Overflow (CSO) in a typical year in response to their USEPA Consent Decree requirements. The Fleet Avenue project is the first GI project to be installed within the Sewer District s combined sewer area to meet the requirements of the consent decree. PROJECT GOALS The City of Cleveland and the Sewer District jointly sponsored major improvements along Fleet Avenue from Independence Avenue (I-77) to Broadway Avenue in the historic Slavic Village neighborhood of Cleveland. The City of Cleveland developed the project with the goal of replacing aging infrastructure and constructing Cleveland s first complete and green street. The goal of the overall project was to create a Complete and Green street, which would transform the corridor, generate economic development, while incorporating an innovative Green Infrastructure system that would support a sizeable and measureable reduction in annual CSO. Green Infrastructure Target Areas
GREEN INFRASTRUCTURE PLANNING The GI project area is located along Fleet Avenue, a historic urban corridor within the City of Cleveland. Fleet Avenue is the central commercial corridor in the Slavic Village neighborhood. Currently commercial activity is low, and vacancies are high in the Fleet Avenue corridor. Public investments in streetscape projects have traditionally help attract new private investment, and redevelopment, in neighborhood commercial corridors in Cleveland. Project area map The initial GI design concept along the Fleet Avenue corridor proposed to install a series of linear bioretention areas within curb bump-outs to capture and infiltrate wet weather flows. The design challenges encountered in this scenario were: Constructing a new GI measure within dense urban environment with limited ROW The number and elevation of existing utilities within the right-of-way The typical roadway section limited the flexibility of the GI measure Increased GI maintenance costs due to physical separation In response to these project challenges, the design of the GI control measure evolved throughout the project from multiple small-scale bioretention areas within the right-of-way to a separate storm sewer collection system with a central GI control measure located outside the right-ofway, utilizing vacant city lots abutting the corridor. Several vacant lot locations, each held in the county land bank program were evaluated. Ultimately the vacant lot which captured most runoff at the lowest cost was selected. SOILS Geotechnical investigations confirmed the presence of subsurface sandy soils within 6 feet of the surface in the project area. This sand layer was approximately 20 feet in depth. These high permeability soils presented ideal conditions for maximizing storm water
infiltration. Infiltration rates were modeled using conservative values. The infiltration basin was located where sandy soils where within 6 of the surface. DRAINAGE AREA In order to remove storm runoff from the existing combined sewer system, a new separate storm sewer was designed. This separate storm sewer system was 1500 long and now collects 15 acres of runoff and has capacity to collect a 19.4-acre drainage area including future rooftop storm sewer connections. Drainage area plan BASIN DESIGN The final GI control measure utilized a 1/3 acre vacant lot as the site for an engineered infiltration basin. Design goals were to receive storm sewer discharges into a rock bed constructed on top of the existing sandy soils. A forebay traps debris from the storm sewer. Rock bed provides void storage for underground storage of storm water. The basin only very rarely would have any open water storage which could present safety issues. Later in the design process a network of storage pipes within the rock bed was added to further increase storage capacity and further decrease the frequency of open water events. Slopes surrounding the basin are designed as stepped walls with landscaping for improved safety. Buffer plantings and a decorative fence will deter the public from entering the basin. HYDRAULIC MODELING Modeling indicates that open water in the basin may only occur from design events greater than the 10 year design storms. The basin can contain a 25 year storm, storms in excess of that will over flow back into the combined sewer.
Pipe Network Stone and Walls AESTHETICS Aesthetic design goals were to create a micro park with a sitting area located at the street corner, providing a green space in a neighborhood lacking in open space. Landscape design used a formal European garden look. The Sewer District designed interpretive signage which explains storm water functions to the public.
Raised Planters Surface Design Typical Cross Section
CONSTRUCTION Construction of the rehabilitated street took 32 months; construction of the GI basin took 10 months. Basin excavation confirmed the presence of sandy subsoils. Construction work was constrained by the proximity of neighboring structures. Preconstruction photos were taken to carefully document preconstruction conditions. Basin under construction
PROJECT COSTS Total projects costs were $8.7 million for reconstruction and streetscape construction of 3600 LF of street, and rehabilitation of 1600 LF of street. Green Infrastructure projects were $1.7 million including engineering, property acquisition, and construction costs. This cost translates to $0.36 per gallon of stormwater reduction. Completed project MAINTENANCE A significant factor in design was minimizing long term maintenance. Maintenance requirements for one centralized basin dozens versus numerous distributed roadside bioswales are significantly lower. The Sewer District, who is responsible for maintenance, chose the larger basin, as easier to maintain. The Sewer District has subsequently contracted for a maintenance program to maintain their portfolio of GI measures. MONITORING The Sewer District is monitoring the performance of the GI control measure with level sensors, flow monitors, and rain gages. The goal of the monitoring is to determine the actual functionality of the GI control measure. A monitoring program has been contracted by the Sewer District, and is now underway. PROJECT BENEFITS The separated storm sewer network will collect runoff predominantly from the right-of-way. The infiltration basin will combine an extensive engineered subsurface pipe system in order to increase storage and provide infiltration with a vegetated park like surface to provide aesthetic, open-space, and water quality benefits for the surrounding community. The GI System will provide an approximate annual CSO reduction of 0.8 million gallons (MG) and capture 4.7 MG of annual storm water runoff.
GREEN INFRASTRUCTURE COBENEFITS In addition to CSO reduction the project provides multiple other benefits: Plants provide storm water interception and evapotranspiration Plants remove nutrients and increase suspended solids sequestration Neighborhood beautification Neighborhood amenity Economic stimulus and community redeveloment Public Education