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Project Designers Chris Sonne & Chris Hale (Bioform Landscapes)
Civil & Environmental Services, LLC is proud to be the design engineer selected for the Greening of Virginia's Capitol Project. This project consists of multiple and diverse sustainable site design elements to be constructed on and around the grounds of the State Capitol in Richmond, Virginia.
The primary goals of this project are to implement a variety of innovative storm water management approaches in a high-profile urban environment. To accomplish these goals, we are working closely with Bioform Landscape and Environmental Design, the Dept. of Conservation and Recreation, Dept. of General Services, and the City of Richmond through an integrated design process.
Project funding is provided under a National Fish and Wildlife Foundation (NFWF) grant.
This project has been selected as one of the four Sustainable Sites Initiative (SITES) Pilot Project located in Virginia. The SITES program is a points-based site certification program that supports sustainable design and construction of site-based projects (parks, campuses, etc.). More information on this program may be found at www.sustainablesites.org/pilot
There is a project website for Greening Virginia's Capitol that contains additional information about the project and those involved with it - www.greenvacapitol.org
The design elements utilized on this project are described below.
PHASE I - POROUS BRICK PAVERS
The existing brick steps and walkway to the east of the Capitol building have been replaced with porous brick pavers, and a new porous brick paver walkway has been constructed to improve pedestrian movement through the site. Based upon the system design and existing soils conditions, these new porous walkways will capture and infiltrate all the rainfall from a 10 year storm. By reducing the amount of stormwater runoff from the site, the total pollutants from the site is also reduced.
Photos of the construction phases from beginning through completion are shown below.
PHASE II - BELL TOWER RAIN GARDENS
Three rain gardens have been constructed around the existing Bell Tower building on the Capitol grounds. Due to poor soils, two of these can not achieve adequate infiltration, and are provided with an underdrain system. The flows from this underdrain will be diverted to a rainwater harvesting system (Phase IV). The third rain garden is located on soils with excellent infiltration capacities, and did not require an underdrain.
A unique feature of this site is the existence of a small spring (which is currently diverted to the City of Richmond sewer system). This spring is diverted into an area of the rain garden that will be planted with wetland vegetation. After passing through the planting soils, the spring flow enters the underdrain system.
Vegetation for the rain gardens consists of native Virginia plants selected to thrive in the specific conditions (very wet, but drought tolerant).
Photos of the Bell Tower rain gardens before, during and after construction are shown below.
PHASE III - BUS LOOP BIORETENTION PLANTERS
The Bus Loop (Capitol Street) is a limited access road and parking area located adjacent to the Capitol grounds (to the North). Storm water in this area was previously routed to two existing curb inlets. Under this phase, seven bioretention planters were installed to intercept storm water runoff and provide treatment and volume reduction (approximately 750,000 gallons per year). A large infiltration gallery is incorporated under the planters to maximize the amount of rainwater to be captured and infiltrated. Under heavy rain conditions, excess runoff will flow to the existing storm water system.
Each planter captures storm water from the gutter. When the depth of water in the planter reaches about 6 inches, the water backs up and prevents additional water from entering. Excess storm water flows past the full planter to the next planter. Whatever storm water is not captured by these planters flows to the existing City storm water inlets.
Photos of the Bus Loop planter site before, during, and after construction are shown below.
PHASE IV - RAIN WATER HARVESTING SYSTEM
A rainwater harvesting system will be implemented to capture a combination of surface runoff and underdrain flow from the rain gardens (including a small amount of spring water flow). This system will consist of four parallel cyclonic pretreatment filters, 10,000 gallon underground tank, submersible multi-stage turbine pump (with variable speed drive), filters and controls. Provisions are included to add UV disinfection to the system in the future, if deemed necessary.
Harvested rainwater will be used to supply the existing ornamental fountain, as well as three existing irrigation zones in the area. The existing irrigation supply system will automatically supply back-up water in the event there is not enough harvested water. Meters to measure the amounts of recycled and back-up water through this system will be provided to document the system's effectiveness.
This system is currently scheduled for installing in the spring of 2012.
PHASE V - 9TH STREET BIORETENTION PLANTERS
Multiple bioretention planters will be constructed along the section of 9th Street that is adjacent to the Capitol Grounds (between Bank Street and the vehicle entrance).
This installation includes a mix of planters with and without infiltration capabilities. Trees have been incorporated into two of the planters, and native shrubs, perennials, and grasses will be used in all planters. The planter structures are constructed adjacent to the existing curb, taking up half of the existing ~13' wide sidewalks. They capture runoff from the existing curbline, diverting it into the bioretention area. Excess runoff discharges back to the existing gutter and storm water system. Due to the slope of this street (~6.5%), weirs are integrated into the planters at approximately 10' spacings to control the flow and encourage maximum infiltration over the planting medium. These weirs have been constructed from existing 6" wide granite curbing.
The first two of these planters have been completed. Four additional planters will be installed in spring of 2012. Photos of the first two planters are shown below (before, during, and after construction).