Lancaster’s Green Infrastructure Plan provides a strategy to manage stormwater runoff with techniques that are cost-effective and responsible.
(2011) Prepared by CH2M Hill for The City of Lancaster, PA. The City of Lancaster is one of about 770 cities nationwide with a combined sewer system (EPA). Combined sewer systems collect and transport both domestic sewage (wastewater from plumbing in buildings) and rainwater that flows from downspouts, streets, sidewalks, parking lots and other impervious surfaces common in urban areas. Eighty-five percent of the time, the City’s Advanced Wastewater Treatment Facility is able to manage and clean the volume of wastewater flowing through this combined system. However, during intense rainstorms and other wet weather events, the system becomes overwhelmed. Each year, this causes about 1 billion gallons of untreated wastewater (mixed sewage and stormwater) to overflow into the Conestoga River. These events are referred to as combined sewer overflows (CSOs) or simply “overflows”.
A summary of the results from the Green Infrastructure Benefit Calculator for both the 5-year and the long-term implementation periods is included in Table 5-11. Given the inputs and assumptions discussed, the green calculator estimates that long-term implementation of green infrastructure can reduce the average annual stormwater runoff in the study area by over 1 billion gallons per year, total suspended solids by 1,457,000 pounds per year, phosphorus by nearly 30,000 lb./yr., and nitrogen by over 60,000 lb./yr. The total capital/implementation cost of this program in 2010 dollars is estimated to be $141 million, although the marginal/increased cost of incorporating green infrastructure as a part of other projects is estimated to be only $77 million. Perhaps most importantly, the estimated cumulative total cost per gallon CSO reduction ($0.18/gal) is quite competitive with the preliminary cost of a large storage tank in the North basin ($0.23/gal). Furthermore, the estimated cumulative marginal cost for green infrastructure, $0.10/gallon, is significantly less than that preliminary cost for gray infrastructure.
The report includes several high profile green infrastructure projects at public sites.