Philadelphia Green Infrastructure Video

7 09 2010

I recently came across this video covering Philadelphia’s Green Infrastructure Efforts. It was created by GreenTreks, an award-winning Philadelphia-based non profit communications organization dedicated to educating people about the interconnectedness of environmental, societal, economic, and individual health. For more information and links to other resources on Philadelphia’s triple bottom line green infrastructure strategy  see our past post  Triple Bottom Line of Green Infrastructure.

Brian Phelps





Metro Green Infrastructure Master Plan Now On-line

1 09 2010

Metropolitan Nashville-Davidson County’s Green Infrastructure Master Plan is now available on Metro Water Services’ website. The plan was prepared by amec, Hawkins Partners, Urban Blueprint, and the Low Impact Development Center. The plan includes the following:

  • Green Infrastructure Practice – Overview of Green Infrastructure and descriptions of various practices.
  • Technical Analysis of Green Infrastructure – Analysis of the CSS area with respect to green roofs, three kinds of infiltration practices, tree planting, and rainfall harvesting (cisterns and rain barrels) and its potential impacts on the CSS.
  • Green Infrastructure Projects – Brief overview of the preliminary design concepts for six projects.
  • Green Infrastructure Incentives and Financing – Summary of various potentially applicable incentive practices that have been applied in other cities to encourage the use of Green Infrastructure.

Click here to download the entire plan in PDF format





Deaderick Street Discussed at StormCon 2010

20 08 2010

Kim Hawkins, a principal with our office, recently spoke at this years StormCon in San Antonio, TX. She and Jim Snyder P.E., who at the time of the design and construction of the street was with Metro Nashville Public Works and who is now with Metro Nashville Water Services , spoke about the process of bring Nashville’s 1st Green Street to fruition. The following is the abstract about the presentation.

ABSTRACT: DEADERICK STREET – TENNESSEE’S 1ST GREEN STREET

Nashville, TN

Nashville Metro Public Works, Client

Hawkins Partners, Inc worked with the Office of the Mayor and Metro Public Works to transform a historically and civically significant corridor in the downtown area which serves as a physical connector between the city/county courthouse and the state legislative arm of government. Prior to the renovations, the street had become most widely known as the central transfer point for the Metro bus system. In the fall of 2008 the bus system’s hub was relocated one block north to the ambitious Music City Central, presenting an opportunity to re-envision the street itself.

Deaderick Street sits within the Kerrigan Basin, one of Nashville’s Combined Storm Sewer (CSS) basins, that has historically been subject to overflows., it is Nashville’s first implementation of LID features in the public right-of-way, the first green street in Tennessee and one of the first green street applications in the southeast. The renovations to the street primarily focused on addressing stormwater issues and urban trees.  Pervious surface within the right of way was increased by 700% through the use of rain gardens, pervious concrete and .bioswales were implemented in pedestrian bulbs at the intersections.  The site design worked within the context of the existing street and the existing storm drainage system, retrofitting existing storm drains to serve as overflow only. Rain gardens and bioswales were designed with engineered soils to allow infiltration and planted with plants, including many natives, that are adaptable to the extremes of wet and dry conditions. Based on Nashville’s historical rainfall patterns, infiltration rates and variable design factors, it is estimated that over 1.2 million gallons will be removed from the CSO system on an annual basis through this three block urban street..

In addition to the stormwater aspects of Deaderick, a number of other sustainable features were incorporated into the street, including LED lighting, recycled steel site furniture, crushed concrete as base aggregate material, fly ash for concrete and solar powered parking meters.





Density as a Best Management Practice (BMP)

4 06 2010

High Point Neighborhood mentioned in Ped Shed Post
photo credit: sitephocus.com

The Ped Shed, a blog focused on walkable urban design and sustainable placemaking by Laurence “L.J.” Aurbach, recently had a post about density as a best management practice (BMP). The post provides a good outline of the evolution of the stormwater regulatory environment. The main point of the post is that well intentioned stormwater regulations make it difficult to build dense walkable environments that ultimately exacerbate stormwater management issues.

The author states:

“But the universal and inflexible application of BMPs and LID can have significantly negative consequences on the quality of urban places and the health of watersheds. LID purports to encourage smart growth and urban redevelopment, but as a rule this support is nominal, little more than lip service. In general practice, LID puts urban density at a competitive disadvantage.”

He cites three studies, two by the EPA (Protecting Water Resources with Higher-Density Development, Using Smart Growth Techniques as Stormwater Best Management Practices) and one by Jacob and Lopez (Is Denser Greener? An evaluation of higher density development as an urban stormwater quality best management practice.) All of them provide compelling data as to the benefits of density with regard to stormwater run-off and pollutant loads, and are well worth reading.

I agree with him that when developing an urban vs suburban site, more expensive stormwater BMPs are typically utilized (i.e. underground detention, green roofs) to meet stormwater regulations.

However, site area, property costs, and market dynamics are a large factor in determining appropriate BMPs and cost effective solutions. If you can build significantly more square footage due to a better market environment and/or need to maximize your investment in land cost (which often reflects the market potential and property entitlements) then the cost of best management practices that maximize these potentials can be offset.

The examples of offsite mitigation are very intriguing. I wholeheartly agree that opportunities for this on properties in close proximity to the development is an effective way to mitigate stormwater impacts while spreading (and hopefuly lowering) the cost across multiple properties. In regard to infill developement, this can be very difficult in practices but not impossible. Public space can be designed to accommodate the needs of neighboring properties. Using green roofs, pervious pavements, and other BMPs on surrounding properties can greatly reduce the volume of runoff being diverted to these offsite areas and therefore their size  can be diminished to a point that can be integrated better into urban environments.

-Brian Phelps





BLUE is the New Green

16 04 2010

I think I may have heard the term “blue roof” before last Saturday, but I must not have paid attention.  I was fascinated as I read New York City’s NYC Stormwater Sustainability Report 2008. It included a full description of a blue roof as an LID measure.   I checked out  few other leads to find this LID technique also being explored in Washington state and a recent article in EDC Magazine discussing it as well.

Bottom line:  a blue roof detains water on the roof of a structure in order to reduce the stormwater impacts.  The detention is done through a  flow restriction device around the roof drain which slowly releases the water or, in the Washington modeling, all of the rainwater on the rooftop is collected and stored.  The roof-harvested water can used to fill a water cistern for irrigation, a site infiltration system like a bioswale or rain garden or discharged slowly to the storm system.

The blue roof is best suited to a large flat roof in more urban areas with limited availability of ground level detention.  There are also designs which provide wide “gutters” near the perimeter of the roof to concentrate the water roof load where it can be supported structurally.  If the primary goal is stormwater reduction, then a blue roof can achieve that goal at considerably less cost than a vegetated green roof.  The estimates I found ranged from $1/s.f. to $4/s.f. for a blue roof while estimates for an extensive green roof might be $18-25/s.f.   Blue roofs also don’t have the same maintenance costs of green roof either – they basically require the same maintenance as a conventional roof..

Of course, the blue roof doesn’t provide the multi-benefit that green roofs do (such as energy use reduction, habitat, aesthetic, life cycle roof cost), but 2008 modeling conducted by Douglas Beyerlein, PE, Clear Creek Solutions in Mill Creek Washington does show the blue roof slightly outperforming the green roof for stormwater reduction.

-Kim Hawkins





Eco-roofs in Portland: Creating Habitat [VIDEO]

2 04 2010

Screenshot of KGW News Story

I came across this news segment from KGW News in Portland regarding the City’s eco-roof initiative and the recent visit by Dusty Gedge, president of the European Federation of Green-roof Associations. In addition to many of the other benefits of green roofs, the city is also promoting the creation of eco-roofs to establish habitat for dry riverbed species in particularly the diverse species of birds that migrate through the city. I couldn’t embed the video but here is a link to it and the transcript.  Tom Liptan, an Environmental Specialist with Portland’s Bureau of Environmental Services, summed it up well by saying.

“The benefit of an eco-roof is that it provides habitat for various species that are losing that kind of habitat in most urban environments around the world.”

-Brian Phelps






Zoning and Pervious Pavement

19 03 2010

This month, the topic of APA’s Planning Advisory Service’s column, “You Asked, We Answered”, is how zoning codes across the country are handling pervious pavement for parking and sidewalks. The links to the various zoning codes were very useful. The following are excerpts from some of the more interesting ones.

ASHEVILLE, NC

“Porous paving blocks and pervious paving materials are permitted and encouraged as material for parking lots. The use of grass as a parking lot surface is permitted for overflow and intermittent parking. Pervious paving systems are required for parking spaces which exceed the maximum number of spaces required by subsection 7-11-2(c). The use of grass or other vegetation as a parking surface is permitted only for parking spaces which are provided in excess of the maximum number of parking spaces required by subsection 7-11-2(c) or used for intermittent or overflow parking. Parking lots associated with arenas, sporting facilities, amphitheaters, fairgrounds, and religious institutions may, however, use grass or other vegetation for the entire parking lot.”

DOUGLAS COUNTY, MN

Impervious Surface Replacement. Existing properties exceeding the standards for impervious surface coverage present a distinct management challenge from that of newly developed properties and there is a need to establish clear and consistent guidelines for how re-development of these lots may occur.

1. The applicant removes existing impervious surfaces at a ratio of one and one-half (1.5) square feet removed for every one (1) square foot added and restores these areas to a permeable surface…

…a. Permeable pavement systems are encouraged in the management of sites currently over the impervious surface limit and shall be credited as twenty-five (25) percent pervious for these sites when installed according to the requirements of

Section V.L.4.a.(2.)(d.)iii. Applicants are encouraged to replace existing impervious surfaces with natural vegetation at the 1.5 to 1 ratio listed above, however, permeable pavement systems may also be used. In these cases they are to replace existing impervious surfaces at a ratio of at least four (4) square feet converted for every one (1) square foot of new impervious surface being added;

2. The applicant removes existing impervious surfaces at a 1:1 ratio and restores those areas to a permeable surface and in addition, submits a comprehensive stormwater management plan that emphasized infiltration and onsite retention of stormwater for at least the two year 24-hour storm event through a combination of methods including buffer strips, swales, rainwater gardens, permeable pavement systems and other low impact development methods. The stormwater management plan must be designed by a registered engineer or landscape architect and installed as designed by a qualified professional.

a. Permeable pavement systems may be considered as 100% pervious when submitted as part of a stormwater management plan consistent with this section…

FT. WAYNE, IN

If construction techniques such as pervious pavement, block and concrete modular pavers, and grid pavers are used for off-street parking surfaces, each space provided as a result may serve in lieu of two (2) required off-street parking spaces, up to a maximum of 10% of the number of required spaces…

…Paving and drainage. All land which is placed in use for off-street parking and all driveways serving parking, delivery, and loading areas, shall be paved with asphalt, concrete, or other approved all-weather hard surface, including construction techniques such as pervious pavement; block, concrete, and similar modular pavers, and grid pavers; and shall be drained with materials and in a manner which meets the current minimum standards and specifications for parking areas adopted by the Board.

-Brian Phelps