Wednesday, March 20, 2013

Where Can all the Water Go?

As municipalities and professionals attempt to envision new and innovative approaches to stormwater management, BSG has taken a leading role in searching for novel applications and effective solutions.

Many cities in the northeast corridor,  such as Philadelphia, are confronted  with the challenge of older sewer systems, which combine sanitary and storm sewage in the same piping.  While this was deemed an efficient system in previous eras, the federal EPA has begun to regulate and fine the discharges from these system into waterways like the Delaware River.  In response, an ever growing field of green stormwater management has developed, and BSG has been on the forefront of the investigation and conceptual design of new systems that can separate stormwater from sanitary flows.

The basic premise of most of these green designs is an attempt to remove a portion of the stormwater flow prior to it entering the CSO (Combined Sewer Operating) system.  This can be done in a number of ways, from diverting the flow into raingarden areas and what are referred to as Bioswales, to the development of stone storage trenches which capture and, based upon the soil conditions, either infiltrate or store and slow release the first 1” of rainfall.  This involves calculations of volumes based upon drainage areas and the development of strategies for the mitigation of green acres.

Birdsall has been instrumental in looking at alternative design strategies, such as porous paving, and the use of open space in the management  process. We have also created a design for a Curb Infiltration Unit (CIU) which can be placed flush with a curb and can divert water to feed adjacent shade trees and plantings.  This system provides a more direct means of infiltration and has shown to be of benefit to the nearby plantings.  These units can also be linked with other storage  methods to provide a larger infiltration system.

Many of these ideas have been developed as pilot projects and are now being implemented on a city wide basis.  BSG is working to remain in the forefront of these efforts and to consistently move the bar for creative stormwater management ideas that have practical applications.

Thursday, January 31, 2013

Andy on Sandy: Under the Boardwalk

From the time my mother would let me, I spent my high school and college summers (80’s and 90’s) working at the Coin Castle on the Seaside Heights boardwalk, and surfing Casino Pier.  In spite of that experience, I went on to secure advanced degrees in marine engineering and a career in coastal infrastructure.  I even married a bartender from Sawmill.  This is an unmitigated “Seaside Trifecta.”
With that experience in hand, Sandy-impacted boardwalks are a matter of great interest to me.  We are designing their reconstruction in the BSG offices, and cajoling FEMA to pay for their replacement.  Another of my comrades, Dennis Giuliano, has similar interests (he’s more of a Lavallette trifecta wannabe), and we set out to take a look at the Monmouth and Ocean County boardwalks to see what worked (and didn’t work), and why.  You can link to our report by clicking here.

Suffice to say, the key is not letting waves get “under the boardwalk.”  As we all know, nothing good happens under there.  In the case of waves, they tend to impact the girders, stringers, decks, etc. and rip them to pieces.  The only time “under the boardwalk” works is if the deck is so high that the waves can simply pass underneath and go on their way toward destruction of houses and roads (not exactly a good outcome either).

What we do know is that preventing waves from getting to the boardwalks (big beaches, dunes, seawalls, revetments) works.  Alternatively, causing waves to rise up and over the boardwalk using the same types of structures worked too.  The thought that we can just rebuild the structures “stronger” is unrealistic.  For the same reason that offshore oil structures and well-designed recreational piers are so high (e.g. Atlantic City, NJ; Huntington Beach, CA ) it is clear that getting boardwalks out of harms way is the preferred solution – not simply reinforcing the structure to withstand the awesome power of wave impact.

The bottom line here is cost.  There is a premium associated with protecting boardwalks and other coastal structures from harm.  As I’ve inventoried the damage over the last several months, it is very clear that coastal structure survival is less about engineering than it is about the foresight of owners to see that this was coming and protect their investments.  Investment in resiliency is the number one consideration that we will face as we reoccupy and rebuild.  It is not always a certainty that resiliency is the right solution.  Sometimes cost considerations render a structure “sacrificial,” and we’d rather abandon or reconstruct after a storm.  Sometimes, financial considerations give us no choice but to take our chances that Sandy Part II doesn’t arrive in our planning horizon.  I like to help people make those decisions in an informed way --- that’s my job.