Transnational knowledge exchange on SUDS case study: permeable pavement

Transcription

1 Transnational knowledge exchange on SUDS case study: permeable pavement Boogaard F.C. *+***, Blanksby J.**, Ven F.*, Chris Jefferies*** * Delft university of Technology. Department of Sanitary Engineering, Faculty of Civil Engineering and Geosciences, Delft University of Technology, P.O. Box 5048, NL-2600 GA, Delft, the Netherlands ** Pennine Water Group, Department of Civil and Structural Engineering, University of Sheffield, UK *** Tauw bv, Zekeringstraat 43 g, 1014 BV AMSTERDAM, the Netherlands **** Urban Water Technology Centre, University of Abertay Dundee DD1 1HG corresponding author: Floris.Boogaard@tauw.nl, f.c.boogaard@tudelft.nl KEYWORDS: Transnational knowledge exchange, innovative SUDS, stormwater quality, maintenance, design, monitoring, permeable pavement ABSTRACT Transnational knowledge exchange is an essential part of raising awareness of the performance of SUDS in different circumstances or countries. Although the concepts of sustainable urban drainage systems (SUDS) are widely understood, little attention has been given to how to optimize these systems to improve the hydraulic benefits and removal efficiency of SUDS to achieve water quality and quantity standards or other aspirations. Under the flag of the project Skills Integration and New Technologies (SKINT) UK, Norway, Germany and the Netherlands, experiences in SUDS are being exchanged by international activities such as workshops, fieldtrips, job rotation etc. Examples of well constructed SUDS are quite easy to find, but failing SUDS can be more beneficial in illustrating the consequences of poor design and construction of SUDS. Examples of the impact of poor design and workmanship on the performance of SUDS include: reduction of the infiltration or storage capacity, reduction of the discharge capacity and pollution of soil and groundwater. This is illustrated by an on site monitoring programme and a review of case studies in the Netherlands where permeable pavement was clogged immediately after construction due to bad design or construction. In general the infiltration rate of these infiltration facilities can be high after (adequate) construction. In other cases, the infiltration capacity deteriorated over the years and in some cases has become little different than that of regular pavement. Common failures in the design, construction and maintenance of SUDS were gathered from several international locations and translated to the following recommendations. INTRODUCTION Transnational knowledge exchange plays an important role in spreading information about and implementing SUDS around the world, but structured transnational exchange is currently underutilized in this respect. This is recognized in the project Skills Integration and New Technologies (SKINT) which emphasizes the need for speaking a multi disciplinary language to integrate the worlds of spatial planning, urban design and water management. SKINT is encouraging the implementation of innovative technical and sustainable solutions around the North Sea Region which have already proved to be successful. It is also encouraging their adaptation for application in circumstances different to those for which they were originally conceived Several SUDS were tested for their hydraulic behavior and removal rate as. These included infiltration trenches and basins, (slow) sand filters, soakaways, ponds, swales, stormwater wetlands and bioretention, filter strips, sedimentation basins, (lamella) filters and permeable pavements. International knowledge exchange in the laboratory of TU Delft as illustrated in the adjacent picture has taken place to show several municipalities and water boards how SUDS function. Several organizations were interviewed to determine their lack of knowledge. One of the topics was which criteria do you use to determine the selection of SUDS, the most common criteria were: 1. removal efficiency,

2 2. cost (building and maintenance), 3. required space, 4. experience maintenance 5. esthetical 6. robustness 7. life cycle analyses 8. sustainability International case studies Examples of well constructed SUDS are quite easy to find, but failing SUDS can be more beneficial in illustrating the consequences of not designing and constructing SUDS properly. Examples of the impact of poor design and workmanship on the performance of SUDS include: reduction of the infiltration or storage capacity, reduction of the discharge capacity and pollution of soil and groundwater. Examples: SUDS: lamella filter (Netherlands), sedimentation basin (Netherlands), swale (Scotland), pervious pavement (Scotland). TUD 2011 Reviewing SUDS from different projects in Europe showed that the uncertainties in design can have a large effect on the performance of the systems. Lack of knowledge about the functions and maintenance of SUDS leads to diminished performance which can result in flooding or pollution of the environment. Examples: International educational SUDS: sediment load in stormwater basin, insufficient hydraulic capacity of swale, clogging of a infiltration system and bad construction of inflow. TUD 2011 In several countries as the UK, Germany, Norway and the Netherlands, experiences in SUDS are being exchanged. These are described in this paper and particular attention is given to permeable pavement. It s a widely used system in Europe and America, but little on site monitoring data has been published and there has been minimal exchange of experiences and recommendations to increase the lifespan of these facilities under specific circumstances. An on site monitoring programme was carried out following a review of case studies in the Netherlands where the permeable pavement was clogged right after construction due to bad design or construction. Permeable Pavement Pervious pavements can be defined as porous pavements or permeable pavements based on the surface type. Porous pavements can be constructed with pervious paver materials where water can infiltrate through the entire surface area. Examples of porous pavements are grass surface pavements, gravel surface pavements and porous (asphalt) pavements.

3 Permeable pavements In the Netherlands as in other countries it can be a popular SUD to implement because it uses limited space in dense urban areas. Most architects or urban planners are not aware of the risks of clogging of the permeable stones or whole facility. Under specific circumstances, lack of maintenance the infiltration capacity can reduce to the level of regular pavement in months or years. In most cases the cost of these systems are twice as much of that of regular pavement. In some designs gullies are not mot included in order to reduce cost, butr in most cases when clogging occurs this will lead to local flooding. Methodology of research The literature review resulted in experiments around the world mainly in the laboratory or on site experimental set ups (see picture of an experiment by the University of Abertay). Most of the results had high infiltration rates, higher than what is determined on site. Since specific factors are hard to simulate (eg clogging due to atmospheric deposition and leaves) the main focus of this research was on insitu monitoring. The main tool for the on site experiments was the double ring infiltrometer. The infiltrometer is a device used to measure the rate of water infiltration into soil or other porous media. Commonly used infiltrometers are single ring or double ring infiltrometer, and also disc permeameter.. Since the double ring infiltrometer is the most used method around the world from a cost effective point of view it is used for this research to be able to compare international results. Double ring infiltrometer requires two rings: an inner and outer ring. The purpose is to create a one dimensional flow of water from the inner ring. If water is flowing in one-dimension at steady state condition, the infiltration rate is approximately equal to the hydraulic conductivity. A second, larger ring is placed around it with the same waterlevel to prevent horizontal flow of water from the first ring. Water is supplied with falling head or steady state condition, and a data logger records the infiltration rate from the inner ring into the pavement over a given time period. Infiltrometer Double ring device (left), introduction permeable pavement with international projectgroup SKINT at HHNK (water authority in North of Holland, Heerhugowaard) After a literature review, on site measurements were carried out on 10 locations around the Netherlands. At these locations the infiltration rate was measured on 3 different surface categories: driving lane, centre of the road and parking lot. In interviews with manufacturers and municipalities it was stated that the infiltration rate on the driving

4 lane was bigger because suspended solids would be pushed out of the permeable pavement because of the pressure of tyres leading to less clogging. Results In the next table the results from the literary review and on site monitoring are given. The determined infiltration rates from permeable pavement can be very low (6 mm/h) or very high (higher than mm/h) in different locations. At the locations different rates where identified for the 3 different categories identified above. No specific relation was been found to suggest that the infiltration rate of the driving lane is in general higher than at a parking lot. The speed of cars (mostly km/h) can be too low to have the effect of unclogging the facility by tire pressure which is believed to occur on permeable asphalt roads. Indication of infiltration rate in time (most permeable pavement should have infiltration rates of >1000 mm/d just after construction according to manufacturers) TUD 2011

5 Table of results from different locations (most after 1 or 2 years of construction) TUD 2011 Experiment Location Type of pavement Method used Values (mm/h) Different types of Infiltrometer, visual inspection Several locations (7) pavement after rain 0-15 Note Complaints municipalities from NL.Lelystad (Ven) conventional pavement Infiltrometer 9 ~352 On site NL.Utrecht (boogaard, Rijsdijk) Different permeable pavements Infiltrometer 100~10,000 On site Germany, TU Kaiserslautern different locations Permeable (total 4 types) Articifial rainfall & Infiltrometer 36~670 On site Permeable & Porous USA, different locations Pavement Infiltrometer** 29~40,000 On different sites NL Urk Permeable Pavement Infiltrometer 83~209 On site NL Edam Permeable Pavement Infiltrometer 1019~3081 On site NL Heerhugowaard Permeable Pavement Infiltrometer 2372~9730 On site NL Heiloo Permeable Pavement Infiltrometer 1210~1454 On site NL Helden Permeable Pavement Infiltrometer 47~1120 On site NL Meijel Permeable Pavement Infiltrometer 83~1703 On site NL Rotterdam Permeable Pavement Infiltrometer 32~245 On site NL Scherpenzeel Permeable Pavement Infiltrometer 184~848 On site NL Schoonhoven Permeable Pavement Infiltrometer 155~4417 On site NL Sliedrecht Permeable Pavement Infiltrometer 277~1537 On site NL Spijkenisse Permeable Pavement Infiltrometer 83~342 On site NL Stamproy Permeable Pavement Infiltrometer 104~1076 On site NL Warmenhuizen Permeable Pavement Infiltrometer 227~5292 On site NL Werkendam Permeable Pavement Infiltrometer 76~666 On site Discussion The example of permeable pavements illustrates the difficulties that practitioners have in accessing information on the performance of SUDS. Information on performance and in particular, long term performance is limited and there is a clear need to pool data. It is possible that the lack of long term data is a direct result of the way that research projects are realised. This is not a criticism of the quality of the research methodology, but a reflection on the way that projects are funded and how this leads to the cessation of monitoring after a limited period of time. One way to overcome this situation is for owners and managers of SUDS to take ownership of the problem and by working together carry out long term monitoring and pool this information to build up a an effective knowledge base. Conclusion and recommendations An investigation of the functionality of permeable pavements is essential to demonstrate their contribution to the urban water balance (local water infiltration can decrease the chance of flooding by storage and reduce loads on the drainage systems and WWTP). General conclusions can be drawn following a review of a wide range of products and different circumstances in which permeable pavements have been constructed. In some cases in the Netherlands e permeable pavements were clogged immediately after construction due to bad design and construction. In those cases, the results of testing have been excluded, but the problem has been noted. It can be observed from the on site experimental results that the permeable pavement in the first years after construction have infiltration capacities to infiltrate storm water in excess of requirements. However, the rates where lower than expected from manufactures. In general the infiltration rate of these infiltration facilities is lower after some years of use and in some cases is little different than that of regular pavement. Common failures in the design, construction and maintenance of SUDS are gathered from several international locations and translated to the following recommendations. Some of these guidelines are:

6 1. Minimise impermeable areas in the design phase; 2. Permeable pavement and the storage underneath should be accessible at all times for maintenance; 3. Proper design and use of SUDS needs adequate communication between the developers, spatial planners, consultants, architects, engineers and inhabitants 4. Workmanship not only affects the serviceable life of SUDS, it affects their basic hydraulic performance 5. Filters can be required to prevent inflow of course particles into the system from connected roofs 6. Detailed documentation of storm water quality measurements and the performance of SUDS can contribute to the enhancements of database and guidebooks 7. Provide controls to regulate and adjust the system after construction when possible 8. Provide a maintenance guidebook 9. A structured, means of monitoring (frequently inspecting the system) and sharing knowledge will beneficial to the SUDS community. This could be informed by monitoring carried out during the commissioning of SUDS measures prior to adoption of SUDS by municipalities. More detailed research is advised in order to collect representative data on permeable pavement. The focus should be on permeable pavements that are in use more than 2 years. We hope that owners and managers of SUDS take ownership of the problem and by working together carry out long term monitoring and pool this information to build up a an effective knowledge base. 1 REFERENCES Boogaard, F Rombout, J. Kluck, J. en Wentink, R Storm water treatment facilities. STOWA (In Dutch) Boogaard F.C., Blanksby J, de Jong J., Van de Ven, F.H.M, Optimizing and implementation of innovative SUDS by transnational knowledge exchange, guidelines for the design & construction and operation, NOVATECH 2010 Boogaard F.C., Van de Ven, F.H.M, Palsma B, New guidelines regarding the design, operation and maintenance of SUDS in the Netherlands, ICUD 11th, 2008 Boogaard/ Guangcheng Study on the infiltration capacity of permeable pavement TUD, Davies J.W., Pratt C.J. and Scott M.A., Laboratory study of permeable pavement systems to support hydraulic modelling. 9th International Conference on Urban Storm Drainage, Portland, pp13, Sep 2002, citied by Zhang, Dierkes, C., 2008 Pollution retention capability and maintenance of permeable pavements. Jefferies C, Mullaney J, The performance of block paving with and without geotextile in the sub base enny SUDSnet Conference 11/12 May 2011 Ven, F. & Dam, F., Infiltration in the pavement..lelystad Rijsdijk M, Boogaard F, NL Utrecht On sit monitoring permeable pavement