Stormwater Library

resources for stormwater professionals

Archive for municipalities

Stormwater Factoid: City of Philadelphia

The City of Philadelphia owns and maintains over 90,000 trapped inlet catch basins.  Over 13,000 tons of debris are cleaned from the inlets on an annual basis.  The City spends over $46 million each year on operation & maintenance of stormwater BMPs.

Source: Leading Stormwater Management Programs in Pennsylvania


Developing a Stormwater Credit System for Using Trees

The following four municipalities have developed a stormwater credit system for developers who incorporate trees into their stormwater plans:

The issue of quantifying reduction rates can be a difficult one due to the different capacities of tree species. For more information on use of trees as a stormwater BMP, please refer to the recent study on Trees and Structural Soils by the Department of Urban Forestry at Virginia Tech University. Developers and design professionals can also refer to the Green Values Calculator, which allows you to create hypothetical designs using trees and other green interventions and quantifies the results in terms of costs savings and reduction in stormwater discharge.

Over the next several weeks, I will be presenting a series on how the municipalities of Pine Lake, Sacramento, Portland, and Indianapolis each went about changing the local building code to include stormwater credits for trees.

Local Stormwater Management Practices

A research study conducted by James Scholl of Malcom Pirnie and presented at the WEFTEC 2007 conference looked at the myriad of local stormwater management programs across the country – focusing on major differences in organizational structures, funding sources, and the impetus for their development. Some interesting conclusions from the report include:

  • Historically, flooding has been the impetus for creating a local or regional stormwater program.
  • Currently, compliance issues and water quality protection are the forces behind creating new programs or modifying existing ones.
  • Using an existing public works to house the program is the most common approach to organizational structure.
  • Funding for new infrastructure projects is the biggest challenge, even with an existing revenue structure from fees.
  • Recent trends point to municipalities coordinating with other local agencies and authorities to manage stormwater programs. A good example of this kind of model is discussed in a previous post.

Impact of Street Sweeping Programs on Pollutant Reduction

A research study conducted by the Center for Watershed Protection was released in September 2008 detailing findings and recommendations of a 3-year study on street sweeping and storm drain cleanout programs. The study, which was conducted in phases (literature review, program surveys, and field monitoring), cites the difficulty of the research endeavor due to factors such as street sweeping technology, frequency, and operating conditions. Results of the study focus on recommendations such as:

  • targeting critical areas and times of years for sweeping/cleanout.
  • implementing programs that redirect/treat stormwater before it reaches discharge system.
  • expanding programs to maximize the reduction of leaf litter and prevent it from entering the storm drain.
  • conducting additional research that focuses on evaluting current sampling techniques and developing alternative techniques.

The report can be read in its entirety for free here.

A new regulatory approach

A recent study by the National Research Council suggests the framework for regulating stormwater discharge is inappropriately based on principles applied to sewage and industrial waste.  The focus over the years has been on the chemical pollutants rather than on discharge volume.  Urban and suburban planning has dramatically increased these volumes and taxed watersheds, bringing more water and pollutants into our surface waters.

The study discusses a new permitting approach that puts responsibility in the hands of the municipalities.  Recommendations are made regarding surfacing of roads and parking, as well as for systems to detain and treat stormwater. 

A copy of the study can be  purchased online here, where it can also be read for free.