The City of Lancaster continues to implement its progressive 2011 Green Infrastructure Plan – essentially an early roadmap intended to guide stormwater management improvements and environmental initiatives which result in more livable, sustainable neighborhoods. Such neighborhoods extend from the original four square-mile city core to the farthest boundaries with suburban municipalities. Regardless of neighborhood location, a common goal throughout Lancaster City is to reduce nutrient discharges within its Chesapeake Bay watershed. After identifying Shelley Road, a flood-prone street in the City’s southeast annex, as a key green infrastructure focus, the City partnered with RGS Associates to create a stormwater solution which demonstrates Best Management Practices and meets critical nutrient reduction goals.
Shelley Road’s persistent flooding had overwhelmed this street’s aging storm drain infrastructure, led to pressurized flow, and eroded its discharge channel to an unnamed Conestoga River tributary. In addition to addressing these technical challenges, the City and RGS focused upon thoughtful green infrastructure integration to enhance both regional water quality and local neighborhood aesthetics.
This successfully implemented design incorporates micro bio-retention areas, permeable pavers within on-street parking spaces, an underground storage reservoir, and a regenerative step pool conveyance system. Combined, these recent site improvements provide peak stormwater rate attenuation, volume control, water pollutantremoval, and low-energy, non-erosive conveyance to the unnamed tributary.
As with many retrofit projects, the incorporation of Shelley Road’s green infrastructure improvements proved to be challenging, given constrained work areas within the existing street right-of-way and an adjoining storm easement containing conventional piping sandwiched between two residential properties. Private property disturbance and potential loss of on-street parking spaces were of great concern to local residents, but the design team carefully listened to their concerns expressed during several public meetings, and then effectively balanced these concerns with the City’s stormwater goals.
In addition, this low-lying public street has a large, unmanaged, upland drainage area comprised of existing homes, driveways, and lawns. Aging conventional infrastructure lacked the ability to effectively collect and convey stormwater runoff from these areas to the local river tributary in a stable manner. Its existing discharge point was located more than six feet higher than this tributary which, combined with the high runoff velocities, lead to an extremely eroded drainage channel and frequent sedimentation of the waterway. Stormwater runoff capture, conveyance, treatment, and discharge were identified as key components to this project’s technical design.
To successfully address these challenges, RGS incorporated a series of Best Management Practices. Newly vegetated bio-retention areas, permeable pavers with an on-street parking lane, and an underground storage reservoir now capture upland runoff and provide the added benefits of water quality treatment and volume control. Likewise, the regenerative conveyance system incorporates a series of stepped bio-retention plunge pools and stone riffles which reduce the energy of the stormwater discharge to a non-erosive condition as it enters the Conestoga River tributary. Collectively, these stormwater solutions provide both aesthetic and functional outcomes to a complex engineering challenge.