Environment, Coasts, Oceans, & Infrastructure

A number of consultants and academic researchers who have been developing solutions to technical questions regarding the use of permeable pavement are wondering why they are not being used more often.  The reasons we hear about from cities are a.  too expensive, b. too risky, c. can't be maintained, d. the current regulations and specifications still require me to put in a conventional stormwater system which makes permeable pavements too expensive.  It seems to us that most of the technical questions have been answered in the past 10 years, everyone is updating their design guides, and ASCE is putting out guidance.  Is the slow implementation because of lack of information?  Risk-averse, no-reward for innovation decision-making environment?  Or are there still technical gaps that need to be solved and if so what are they?

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John Harvey P.E., M.ASCE
Professor
University Of California
Davis CA
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John:
We have observed the biggest reason in the Houston area is that it takes 8-20 weeks longer to permit when you try something that the local reviewers have never seen before.  And these weeks are not passive waiting weeks, they devour the energy of the design team in meetings, additional submittals, more meetings, all without a guarantee of approval.  I have seen project where it doubles both the design budget and approval time.  Houston and Harris County are getting much better at this as more consultants push the envelope, more things meet the criteria of "having been seen before."   The only concern that I can have with this criteria, is you better hope that the previous time your concept was seen before, that the design consultant dotted all their i's and crossed all their t's otherwise, there could be a lot of baggage attached to your approval.

Green building, LID, or LEED are all relatively newly refound.  We can't expect modern engineers to do things that worked for the Pharoh's in Egypt's golden age without a little administrative burden.   Hopefully that burden is temporary.

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Dwayne Culp Ph.D., P.E., P.Eng, M.ASCE
Culp Engineering, LLC
Richmond TX
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Lack of Code updates would be my guess.  I know in our area, stormwater codes have not been updated since the early 1990s, this many of the proven LID techniques for stormwater management are not "allowed", at least without a variance.  Until local codes/specifications are updated, it's "more difficult" to get new techniques implemented (more hoops to jump through to get a variance).


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Kevin White P.E., M.ASCE
PROFESSOR
University of South Alabama
Mobile AL
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I perceive slow implementation to be related to the balance between regulations, cost, and familiarity.  If there are no regulatory requirements or very clear cost savings that prompt its use, then engineers, developers, and municipalities/DOTs are not incentivized to innovate, as you mentioned.  Also, I think generally municipalities are more cautious to experiment, unless the feds or DOTs have already clearly signed off and used certain pavements.  Municipalities also have crews trained in certain kinds of maintenance and changing gears on the O&M side is costly/difficult.  In Texas, we have heard of fairly significant installation issues for permeable concrete related to achieving uniformity, perhaps that speaks to contractor familiarity/experience.  I think it also comes down to "why change?" and if the water quality, safety/visibility (wet tire spray), or other benefits are not perceived to be greater than the costs and difficulties, then inertia will continue.

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Saul Nuccitelli P.E., CFM, M.ASCE
City of Austin, Watershed Protection Department
Austin TX
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Washington state (and specifically the Seattle area) has been a big proponent of implementing LID technology including permeable pavement. However, smaller public agencies have been resistant to LID for all of the reasons you listed. Maintenance is a huge issue for smaller public agencies that often don't have the money and staff to maintain such facilities. We also run into geotechnical problems--soil permeability can be highly variable in our area due to glacial influences, and therefore LID facilities can't be implemented without an underdrain, or at all. It is not a problem with code restrictions. Washington state has again been a leader in requiring the use of LID technologies. Since 2012, our stormwater code has required prioritizing LID before other technologies, and public agencies usually have to justify why they can't be implemented. In most cases, cost is not a valid justification.

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Christina Curtis A.M.ASCE
Snohomish County
Everett WA
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In Portland, OR, there is a bit of inter-bureau conflict over pervious pavements. The Bureau of Environmental Services would like to see wide adoption for the obvious stormwater benefits. The Bureau of Transportation doesn't want an increased maintenance burden. The Water Bureau doesn't want to risk contamination of water distribution located under such pavement.

The few existing pervious pavement projects in Portland have performed well thus far.

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Tel Jensen
Woodland WA
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Original Message:
Sent: 05-17-2017 11:00
From: Christina Curtis
Subject: Permeable Pavement

Washington state (and specifically the Seattle area) has been a big proponent of implementing LID technology including permeable pavement. However, smaller public agencies have been resistant to LID for all of the reasons you listed. Maintenance is a huge issue for smaller public agencies that often don't have the money and staff to maintain such facilities. We also run into geotechnical problems--soil permeability can be highly variable in our area due to glacial influences, and therefore LID facilities can't be implemented without an underdrain, or at all. It is not a problem with code restrictions. Washington state has again been a leader in requiring the use of LID technologies. Since 2012, our stormwater code has required prioritizing LID before other technologies, and public agencies usually have to justify why they can't be implemented. In most cases, cost is not a valid justification.

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Christina Curtis A.M.ASCE
Snohomish County
Everett WA
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There are strong incentives for permeable pavements (and other LID practices) in the Chesapeake Bay watershed, but we have seen real challenges in assuring the training, competency, and expertise in each of the different communities of practice (from design and review, through construction and inspection) that EACH have to make the right decisions to deliver reliable results.   This has proven particularly challenging in public sector projects balancing experienced contractors and suppliers with low-bid procurement requirements.   One wants to write specifications and bid documents that are specific and restrictive enough to screen out the inexperienced vendors, while providing enough flexibility so that the skilled expert contractors you want have the flexibility to deliver superior work, adapting to site-specific constraints.  

Working with our DOT on a 1.77 ac. pervious park and ride (designed with sufficient capacity to capture and infiltrate the 100 year storm!) we developed training for the state inspectors on the project, who had no previous experience with pervious concrete.   Very tough to put an inspector in the position of rejecting a load of concrete if they have no prior experience with the material - especially if the specifications do not have adequate acceptance testing.


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Stuart Schwartz A.M.ASCE
Sr. Research Scientist
University of Maryland Baltimore County
Baltimore MD
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We have mostly expansive clay in our area and go to great lengths to keep water out of the subgrade.  Wet subgrades have significantly lower bearing capacity.  Permeable pavements have been allowed in parking areas where the soil is suitable and parking is restricted to automobiles.  Special pavement is required for truck paths and fire equipment routes.   I was wondering, "How are spills of toxic materials handled on permeable pavement?"

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James Anderson P.E., M.ASCE
Principal, Anderson Consulting
North Richland Hills TX
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Multiple years-long studies show that permeable pavement has the capability to remove high percentages of heavy metals including dissolved lead (89-98%), dissolved cadmium (74-98%), dissolved copper (89-96%), and dissolved zinc (72-98%). The same studies also found removal of a majority of concentrations PAHs (100%) and mineral oil (97.6%). If you're interested in reading these studies they are: Dierkes et al., 2002 (Germany); Pratt, Newman and Bond, 1999 (Coventry University, England); Clausen and Gilbert, 2003 (Connecticut); and Brattebo and Booth, 2003 (University of Washington). Most of these studies were done on parking lots, anywhere from commercial parking lots, permeable pavers and driveways. However, toxic or hazardous waste spills will usually require removal of the pavement and subgrade to the depth of the spill. The Washington State stormwater manual has criteria that make sites with known contamination, or even within a defined distance away from such areas, including landfills and septic systems, infeasible for permeable pavements unless the contamination is removed within a certain area. Roads with higher traffic volumes, including truck traffic volumes, also usually make permeable pavements infeasible.

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Christina Curtis A.M.ASCE
Snohomish County
Everett WA
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Original Message:
Sent: 05-18-2017 17:02
From: James Anderson
Subject: Permeable Pavement

We have mostly expansive clay in our area and go to great lengths to keep water out of the subgrade.  Wet subgrades have significantly lower bearing capacity.  Permeable pavements have been allowed in parking areas where the soil is suitable and parking is restricted to automobiles.  Special pavement is required for truck paths and fire equipment routes.   I was wondering, "How are spills of toxic materials handled on permeable pavement?"

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James Anderson P.E., M.ASCE
Principal, Anderson Consulting
North Richland Hills TX
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Hello I am from India. Yes the number of research works and number of trials have been made on the permeable concrete. Many Indian young researchers found out to be the solution in the large parking areas and the solution for stagnant water on road sides. 
I hope to see the permeable pavements in the commercial gardens soon.

Will update you when any project got implemented in Surat City.

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Ahmed Abubakar Jariwala BCE, S.M.ASCE
Engineer
Surat
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