The Etna Green Infrastructure Master Plan Project
The project uses innovative site screening techniques developed by Landbase Systems to conceptually locate and size green infrastructure (GI), referred to as Best Management Practices (BMPs). The screening started not with availability of sites but identification and prioritization of high yield inlets via the Etna GIS where GI could be most advantageously sited.
The Etna Borough GIS model was used in tandem with available soils, slope, and other land use/cover data to characterize the individual catchment areas contributing to the Etna combined sewer system. Each of the catchments was associated with a combined sewer overflow.
The calibrated SWMM Etna sewer system model is used to evaluate the impacts of GI BMPs on the volume and rate of flow during the so-
The Borough has already began construction on several of the projects identified in the Plan. This is Phase I of the Green Streetscape Project, completed in August of this year. This project will remove over 500,000 gallons of stormwater from the combined sewer system.
Phase I
- Acreage Managed: 0.598
- Impervious Acreage Managed: 0.470
- GSI Management Strategy: Filter/Infiltrate/Remove
- Runoff Managed: 0.64 MG/yr (640,000 gal/yr)
Cost: $475,000 including engineering (Actual to date)
The first phase involved reconstruction of the east side of Butler Street between Bridge and Freeport Streets as well as the reconstruction of the north side of Freeport Street between Butler Street and Union Alley. This phase involved th installation of 12 street trees, 2300 cubic feet of underground storage that would promote infiltration, 3900 square feet of pervious pavers, downspout disconnection and restatement to new conveyances and related work. Storm water management is essential to water quality in our streams, creeks and rivers. It can also have a dramatic effect on drinking water quality as it reduces pollutants in ground water. As rain water travels over paved surfaces it picks up grit and debris including salt and other pollutants and deposits them into the combined system or into the ground. Collecting this rain water at is source helps to eliminate this from happening.
The project entailed other improvements and traffic calming/safety features: 562 feet of realigned curbing to create bump-
Phase II
- Acreage Managed: 0.65
- Impervious Acreage Managed: 0.425
- GSI Management Strategy: Filter/Infiltrate/Remove
- Runoff Managed: 0.50 MG/yr (500,000 gal/yr)
The Freeport Street Rain Park is designed to manage runoff from the sidewalk and roofs along Freeport Street representing a total tributary area of approximately 9300 square feet. Of this total area approximately 7300 square feet is impervious surface. The rain park itself is approximately 1900 square feet in area with perennial plantings. It uses a high rate proprietary infiltration media to treat and retain entrained solids in collected/conveyed runoff in advance of storage. The facility has 842 cubic feet of subsurface storage and is designed to infiltrate the runoff from a 1.25 inches rainfall event over a 72 hour period. The facility has an overflow pipe that directs excessive RO volume to a nearby catch basin on the corner of Cherry Alley and Freeport Street.
The Love Street Facility is designed to manage runoff from the sidewalk and roofs along Butler Street and Praeger Street conveyed by new piping systems as well as roof runoff from adjacent buildings and other contributing areas tributary to the street such as yards and gravel parking areas. The facility has a total tributary area of approximately 20,900 square feet. The Love Street facility is designed to infiltrate 1629 cubic feet of collected runoff stored in modular storm water storage units (MSSUs) installed under 1800 feet of pervious pavers. In order to install the facility it was necessary to re-
By its nature, the Green Streetscape creates a strong linkage between transportation considerations and the Etna urban context. The Phase 2 of the project therefore includes other improvements and traffic calming/safety features: 554 feet of realigned curbing to create bump-
The project removes runoff from roof, sidewalk and other impervious areas from the combined sewer system and routes it through new conveyances for subsurface storage and infiltration. Based on the completed project, the Phase 2 project will manage runoff from a 0.65 acre area of which 0.425 acres is impervious. This translates into an estimated average of 0.5 MG of runoff managed annually.
- Acreage Managed: 0.829
- Impervious Acreage Managed: 0.638
- GSI Management Strategy: FIRm
- Runoff Managed: 1.08 MG/yr (1,081,204 gal/yr)
Cost: $701,100 including engineering
Streetscape Phase III captured contributory drainage areas are approximately 45,643 square feet (1.05 acres). The proposed improvements included the installation of 490 linear feet of 12” decorative trench drain within the exposed aggregate concrete sidewalks which conveys the sidewalk run-off and the roof run-off from some of the buildings along Butler Street and directs the run-off to one of the two proposed underground infiltration tanks located on Walnut Street and High Street. Also, seven tree pits with grates were also installed in series with the trench drains to allow for addition infiltration along the streetscape. In addition, new landscape bump-out areas were created and the existing impervious areas were removed and converted into planted landscaped bump-out areas. Lastly, three catch basins with FABCO water quality filters were installed along the intersections of Walnut Street/Butler Street and High Street/Butler Street that now direct the street run-off to the infiltration tanks and no longer discharge directly into the combined system.
Tank 1 on Walnut Street has the capacity to retain/infiltrate approximately 9,672 gallons. It also has the capacity to capture and manage approximately 293,924 gallons annually (removal from the combined system).
Tank 2 on High Street has the capacity to retain/infiltrate approximately 21,750 gallons. It also has the capacity to capture and manage approximately 787,280 gallons annually (removal from the combined system).
Therefore, both systems have the combined capacity to retain/infiltrate approximately 31,422 gallons and manage approximately 1.08 MG annually (removal from the combined system).
The Etna Borough School Street Parking Lot Green Infrastructure Project
Freeport Street Rain Park
The Freeport Street Rain Park is designed to manage runoff from the sidewalk and roofs along Freeport Street representing a total tributary area of approximately 9300 square feet. Of this total area approximately 7300 square feet is impervious surface. The rain park itself is approximately 1900 square feet in area with perennial plantings. It uses a high rate proprietary infiltration media to treat and retain entrained solids in collected/conveyed runoff in advance of storage. The facility has 842 cubic feet of subsurface storage and is designed to infiltrate the runoff from a 1.25 inches rainfall event over a 72 hour period. The facility has an overflow pipe that directs excessive RO volume to a nearby catch basin on the corner of Cherry Alley and Freeport Street.
ECO Park Rain Garden
For several years, the corner lot at the intersection of Wilson St. and Grant Ave. sat vacant and abandoned. However, when the Borough of Etna came into recent ownership of the property, we teamed up to transform the site into a beautiful, green parklet for all in our community to enjoy. Etna Borough Public Works removed asphalt from the rear of the site and brought in compost to start soil remediation. To aid in storm water management, a 900 square foot rain garden with 250 square foot drainage swale (1/3 of the total site) was installed. We were also able to plant four large trees with the assistance of Tree Pittsburgh and community members. And just before temperatures dropped, volunteers came together to construct a shadow box fence and rain garden barrier to enhance and protect the site.
