ICPI Foundation Programs
UC Davis recently provided load and rutting data in advance of their report and recommended design guidelines due in the fall. Over five months, the 96 ft long PICP test track with three different subbase thicknesses received wheel load repetitions over three subgrade soil moisture conditions: dry (natural/dry season), wet (subbase and base completely filled with water), and a drained soil (after saturation). The rutting results relate well to base thicknesses provided on page 31 in the 2011 ICPI PICP manual when loads are applied on the soil subgrade in an unsaturated state. Test results with the base/subbase full of water have approximately double the rutting compared to loads applied on sections over the subgrade in an unsaturated state. This was not unexpected.
The challenge for UC Davis when developing subbase thickness design charts is allowing for some rutting based on some degree of saturation (depending on the regional climate) and include its extent throughout the year in structural design. They will provide three subbase thickness design tables: one for parking lots, another for alleys and a third for streets since they receive distinctly different loads. In addition, UC Davis will provide (non-verified/theoretical) design charts using pervious concrete placed under the open-graded aggregates and directly over weak subgrades since they developed models for this under a previous Caltrans contract. We expect a final report with design charts this fall.
PICP test track with heavy vehicle simulator (HVS) with tires for load testing at UC Davis
How the industry can use this: The deliverables will be used in the emerging ASCE PICP national guideline for PICP design, construction and maintenance, as well as in ICPI publications. Pervious concrete and porous asphalt are undergoing full scale load testing by the Minnesota Department of Transportation. Having validated load tests for PICP puts the industry on equal technical footing with competitive systems.
As an aside, in 2012 UCPRC released a doctoral dissertation research report examining the heat dynamics and radiation response of permeable pavements tested at their facility in Davis. PICP received high marks with the highest albedo.
This final report has been submitted and received by the Program Committee as well as the ICPI Technical Committee. The report favorably positions ICP as complying with the roughness criteria using the Pathway Measurement Tool or PathMeT developed as part of this contract. This tool was presented at the 2013 ICPI Technical Committee Summer Meeting in Pittsburgh. Sidewalks roughness criteria for wheelchair users was developed by the University for the U.S. Access Board and these criteria will be noted in the upcoming ADA design guidelines (rulemaking) for the public right-of-way expected later this year. Smoothness criteria will not be included in proposed regulations but will likely appear as non-mandatory guidelines. Official design criterial will very likely happen in a few years according to Access Board staff. The Foundaion and BIA funded the development of cutting edge technology to measure sidewalk smoothness.
The University presented their findings at a U.S. Access Board meeting on September 8, 2014 in Washington, DC with ICPI and BIA staff in attendance. The Access Board was particularly amazed that segmental pavements did comply with roughness criteria using PathMeT. Dr. Pearlman from the University emphasized the need for maintenance in order to keep sidewalks surfaces smooth and comfortable for wheelchair users regardless of the paving materials.
Two other important sideline activities: (1) An ASTM standard for PathMeT is being balloted and (2) PathMeT is being spun off into a private company for developing this sidewalk smoothness assessment tool commercially. This is underway by a few graduating students who anticipate demand increasing for this measurement technology once the ASTM standard is approved and when the ADA design guidelines for the public right-of-way are published. PathMeT is being used to assess the condition of 80 miles of sidewalks in the District of Columbia. Members may want to consider having their products tested in situ using PathMeT as chamfer sizes and joint widths influence results.
The PathMeT device for measuring sidewalk smoothness
How the industry can use this: ICPI/BIA participation helped facilitate a positive outcome and possibly prevents loss of market share. Development of smoothness/vibration standards favorable to segmental pavements could better position the industry over the long term, ultimately selling more pavers. UP is seeking investors to purchase and commercialize PathMeT for use in sidewalk pavement management systems typical to those used by municipalities.
UHNSC has posted their final report on two years of monitoring a 13,500 sf PICP site called Hood House Drive in the university campus center. The 54-page report can be downloaded HERE. The site includes a one page fact sheet on PICP. Also, a two-page project summary on pages 16 and 17 in the UNH Stormwater Center 2012 Biennial Report can be found HERE.
The 13,500 sf (1,350 m2) Hood House Drive and parking lot in Durham, NH, reduced runoff volume and pollutant mass removals some 95 percent. Monitoring water infiltrating from about half of the PICP area included pollutants such as sediments, zinc, petroleum hydrocarbons, and nutrients (i.e., phosphorous and nitrogen forms). Built over moderate infiltration soils, the pavement saw significant volume reductions such that no single rain event generated more than 5 gal (20 L) of discharge for underdrains in the base. Additionally, the study confirmed that open-graded bases and soil subgrades do not heave from winter freezing and thawing.
|Hood House Drive PICP
University of New Hampshire
Key findings from the report:
• Volume reduction and pollutant mass removal exceeds 95% for all contaminants measured including sediments, metals, petroleum hydrocarbons, and nutrients (i.e., total and ortho-phosphorous, total nitrogen and various nitrogen forms).
• Surface infiltration rates declined 69% over 21 months yet retained greater than 1,000 in/hr. vacuuming the surface provided modest increase in the surface infiltration rates. Minimal maintenance was performed during the period of monitoring. The surface was plowed and deicing materials were used as any other pavement. A PICP advantage over pervious concrete and porous asphalt is brining of deicing materials on each paver surface to help reduce ice buildup.
• Thermal analyses were conducted in the summer comparing four pavement surfaces at three different times. PICP surface temperatures were observed to be lower than that for porous asphalt, pervious concrete, and standard asphalt.
• Outreach activities were conducted during 2011 and 2012. Three permeable pavement design workshops were performed for approximately 120 attendees. The training included a field visit to Hood House Drive and other porous pavement installations throughout the UNH campus. Participants learned key design principles necessary to successfully design, evaluate, specify, and install permeable pavements for stormwater management.
This project’s success is due to the Foundation and ICPI jointly funding the $110,704 research contract, plus $48,000 in contributions from ICPI members, the Northeast Concrete Masonry Association, and the Northeastern Cement Shippers Association for materials and construction of the PICP test area. UNHSC is viewed by state and municipal stormwater agencies as a major provider of unbiased design and performance information.
Over the past several years, UNHSC conducted several monitoring studies on pervious concrete and porous asphalt. This PICP study rounds out their research on permeable pavements and suggests PICP as favored for northern climates with porous asphalt. The PICP installation is in a highly visible location adjacent to Main Street and across from the university president’s house. The PICP has been and will continue to be visited by many stormwater officials and engineers that frequent UNH for seminars.
How the industry can use this: Having done extensive research on pervious concrete and porous asphalt, UNH Stormwater Center is considered a key source of information and research on permeable pavements. The PICP research report appears on the UNHSC website. Moreover, ICPI members can use the report to address user questions on PICP cold climate performance. As an additional benefit, an early May 2014 seminar at UNH attended by 100 persons featured this project which was tested for surface infiltration. This is the fourth seminar where the project has been part of the program. Such programs are important influencers of state and local stormwater agencies and designers.
TRCA continues monitoring a parking lot near Toronto with conventional asphalt, pervious concrete and two types of PICP. Initiated in late 2012, the monitoring program provided important insights into the changes in function and treatment capacity of permeable pavements over time. Key findings include the following:
Surface infiltration rates on all three permeable pavements continued to decline after cleaning in 2012, and are now at their lowest levels. Although all pavements continue to infiltrate reasonably well, vacuum maintenance of the PICPs will be required in the next year if they are to continue to function effectively. They have been in service for several years, so cleaning is not unexpected.
The permeable pavements reduce runoff volumes by roughly the same amount as during the first phase of the study, indicating that the native soils below the pavements have retained their capacity to infiltrate and the geotextile below the subbase is not inhibiting the movement of water.
The permeable pavement effluent has lower concentrations of most pollutants relative to that from impervious asphalt runoff. Elevated levels of pH, phosphate and potassium observed in pervious concrete effluent during the first phase of the study have stabilized and trend downwards.
Effluent from underdrains placed above and below a layer of native soil show similar concentrations of pollutants and little change over time. At this site, there was no evidence to suggest that road salts have caused metals adsorbed to the soil to mobilize and the exit as has been suggested by other researchers.
Elevation surveys showed that the permeable pavement surfaces have been relatively stable over time with no obvious signs of heaving, settling or rutting.
The monitoring program is scheduled to continue until December 2014, which would add another year to the data provided in their interim report. Staff recommends the monitoring be continued in a reduced form beyond 2014 to characterize maintenance methods. TRCA may be providing proposals to the Foundation for consideration at the 2015 annual meeting for subject-specific research such as deicer use and outcomes and/or surface cleaning and maintenance trials. This work may be done on a new 10,000 sf PICP street built as part of a sustainable housing development on TRCA property near the current site.
How the industry can use this: Stormwater agencies often request information on pollutant and runoff volume reduction in clay soils and in cold climates. The deliverables from this study provide a significant performance data on these factors. Such information is useful in the PICP education and sales process of designers, stormwater agencies and users.
After a technical hiccup late last year that required NCSU staff finding a new parking lot site, NCSU has monitored rainfall and runoff from 16 rain events from 0.5 inches to 3.5 inches. Infiltration into the subgrade soil averaged 0.036 inches/hour, typical to “Type D” soil, i.e., very slow draining. Storm events less than 0.5 inch have seen an average volume reduction of about 85% through storage and infiltration and with surpluses exiting via a 6 inch raised outlet. The average reduction for storms greater than 0.5 inch is about 65% based on preliminary data. This is excellent considering the clay soil type.
Water quality results are completed for 8 of the 16 storms. In general, all pollutants except for nitrate/nitrite are being considerably reduced. Median total suspended solids concentrations are being reduced from 824 mg/L (control/influent) to 16 mg/L (effluent), a 98% removal efficiency which is superb. Median total nitrogen is being reduced from 2.91 mg/L to 1.21 mg/L, a 58% removal efficiency, and total phosphorus is being reduced from 0.42 mg/L to 0.04 mg/L, a 90% removal efficiency. While total Kjeldhal nitrogen and nitrate/nitrites have been reduced by 89% and 52%, respectively, the median nitrate/nitrite level is increasing from 0.11 mg/L to 0.65 mg/L. This is likely due to the nitrification of nitrate/nitrite which has been observed in several other permeable pavement studies. The researchers need to calculate how much of the pollutant reductions (or additions) is from infiltration into the soil subgrade compared to chemical processes within the effluent outflowing from the underdrain. We expect to receive a report with these answers late in 2014 or early 2015.
How the industry can use this: Deliverables will help address questions from stormwater agencies on nutrient reduction on low infiltration soils, specifically nutrient reductions (nitrogen and phosphorous). Many stormwater agencies regulate nutrients to protect the recreational uses of lakes and streams. Pending favorable results, the report could help demonstrate PICP as a significant tool toward this goal.
|PICP test area in Durham, NC|
The Landscape Architecture Foundation Receives Grant to Develop Educator Tools for Teaching Landscape Performance
Last fall, LAF issued grants and received deliverables this spring from five universities who assessed teaching landscape performance in various university landscape architecture classes and design studios. An additional five universities will compete for five $2,500 grants each in early 2015. The epiphany from the first set of five deliverables was discovering a range of models to measure and describe the performance of ICP as well as PICP.
As a task outside this project, these models need to be articulated to ICPI members via educational tools such as webinars (continuing education presentations) so they in turn can present them to landscape architects. The grant deliverables surprisingly point to possibly developing another education tool for sales by ICPI members. Such an effort would include evaluating the applicability of each model/tool and providing case studies that apply each tool to demonstrate the performance of segmental pavements. LAF is not in a position to do this for ICPIF. Such an effort could support practicing design professionals with better assessment of benefits and rationale for investment in them by project owners.
The LAF website Resources for Educators includes some deliverables from the ICPIF grant. This site offers sample teaching materials for integrating landscape performance into landscape architecture course offerings, including studios, seminar and lecture courses. Materials include syllabi, reading lists, and sample student assignments, as well as faculty reflections on their pedagogical approaches and experiences teaching landscape performance. ICP and PICP receive analysis in most of the deliverables which are about landscape classes learning how to measure/model the performance of a landscape design. The models noted are also listed on the LAF website “Benefits Toolkit” at https://lafoundation.org/research/landscape-performanceseries/toolkit/?b.... Besides the Benefits Toolkit, the Fast Fact library on the LAFoundation.org site summarizes modeled environments by presenting crisply stated conclusions on the measured performance of various modeled landscape systems.
How the industry can use this: This project hold potential to impact educators in developing learning tools for teaching landscape architecture students how to measure performance of landscape designs in general and of segmental concrete pavements in particular. Performance measurement is being demanded by clients of landscape architects and the profession is counting on the universities to train students in such measurement.
Professor John Kevern has completed testing with the different joint widths and jointing stones sizes at various slopes. All tests were run in triplicate with a high level of repeatability. Surface infiltration tests were run before and after to make sure nothing changed during hydraulic testing. The students composing the first rough version of a spreadsheet program for use in designing PICP. Students are also evaluating if orientation of the joints to the flow makes a difference in intake rates. The big item left to do is testing the surface with sediment. Staff met with Professor Kevern on Tuesday, September 9, 2014 to discuss various approaches as well as see the testing equipment in action. A final report is expected in spring 2015.
How the industry can use this: PICP designers have asked about the inlet capacity of PICP, a question that enters into design especially when there is run-on entering PICP from adjacent impervious surfaces and roofs. How much run-on can PICP take before generating runoff? How much run-on can PICP take when in a clogged state before generating runoff? Answering these questions can provide more reliable designs that balance the ratio of impervious to PICP area. In addition, assessing horizontal run-on as a function of vertical infiltration will be a helpful tool for deciding when surface cleaning is required. This information will be included in ICPI publications and in the emerging ASCE PICP national design guideline.
A final draft of the PCR for segmental concrete paving products was reviewed by the ASTM technical advisory group which includes Kevin Earley, Brad Cobbledick, Mike Telischak and David Smith as well representatives from the concrete masonry industry, NCMA staff Nick Lang, Wayne Trusty (an independent consultant working for ASTM), Martha VanGeem, PE (consultant to the ICPI Foundation), and ASTM staff Chris Surak. The draft is very similar to the concrete masonry PCR developed by the same technical advisory group. The draft will be sent to public review by ASTM for from 8/29 through 9/17/14, then to third party review. “Third party” means three independent reviewers which includes a representative from PE International and from two other companies, all experts in ISO standards the specify requirements for PCRs, LCAs and EPDs. Comments from the public review and the third party review will be assessed by the technical advisory group and changes made to the PCR accordingly. This assessment should happen in October which means a target completion date in November 2014. The PCR document is owned by ASTM and will be sold by them.
ASTM C15 committee is currently balloting a concrete paving slab standard. When approved by ASTM and assigned a number (CXXXX), this standard will be included in the attached PCR. The PCR provides guidelines for manufacturers in conducting life cycle analyses (LCA) at their plants and from the LCA data, guidelines for environmental product declarations.
The ICPI Technical Committee received a $15,000 proposal from Ms. VanGeem to develop guidelines for paver manufacturers explaining how to conduct a life cycle assessment. The proposal also includes an Excel template for manufacturers to develop environmental product declarations. This appears to be a logical next step. NCMA plans on developing a similar tool for their members through Ms. VanGeem.
How the industry can use this: PCRs lay the conceptual ground work for paver manufacturers and ICPI in conducting life cycle analyses (LCAs) of paving products. These are required for ICPI and member manufacturers in developing and issuing environmental product declarations or EPDs. Now popularized by LEED v4, comparison of EPDs of various products will become another basis for paving product selection by design professionals, their clients and public agencies.