Placement of Smart Grass reinforcement at test sections Groningen Sea dike

The present report deals with the application of a provisional Smart Grass Reinforcement (SGR) system in 2006 for full scale testing of increased overtopping at the Groningen sea dyke test section near Delfzijl, as envisaged in 2007. The SGR has been placed at two strips of 4 m wide: one primary strip at the basic test site and one at a secondary test strip for additional testing. The placement of the SGR followed the awarding of this system (Report of 10 November 2005) to the consortium of Royal Haskoning and Infram), as the most feasible system for reinforcement of the dyke crest and inner slope of wave overtopped dykes. The activities for the application of the SGR, included pre-engineering, preparations, installation and follow-up. The activities that have been conducted under the responsibility of the consortium of Royal Haskoning and Infram, many other parties contributed as well: subconsultants FlevoGreenSupport and Queens Grass, Huesker (Germany), four students of the Technical College Leeuwarden. Moreover the ComCoast project organization (RWS/CUR and partners Water Board Hunze and Aas, Province of Groningen and Municipality of Delfzijl) were actively involved. The main part of the present report lays down in brief the preparatory activities (Chapter 2), the installation activities (Chapter 3) and the follow-up treatment (Chapter 4). In Chapter 5 conclusions are drawn and recommendations made. Details can be found in the appendices attached to this report: Appendix A: Photographs of situation of the SGR during the inspection visits; Appendix B: Reconnaissance of placement method and type of geosystem; Appendix C: Typical results of grass cover analysis for fertilization (follow-up treatment). The provisional application of the SGR for obtaining a representative test site in 2007 has probably been successful, in spite of many difficulties that had to be overcome. This can be seen from the photographs in Appendix A and Chapter 3. To date, a positive outcome is not sure yet, as there is still doubt on the degree of intertwinement of the grass roots with the geosystem. Hence, further checking of the monitoring strips, next to the test sections, shortly before testing in Mach 2007, will be required to ascertain the required functionality of the SGR. Looking back, the application of the Big Roll method has appeared as not really feasible: elaboration of a smart system for placement, such as indicated earlier by the consortium, should have aimed at from the beginning. A firm statement can be made here that the Big Roll method cannot be made feasible for large-scale application of SGR and further research is needed unconditionally for smart installation techniques of SGR, in combination with a suitable reinforcement system. As regards the unique character of the tests, we certainly hope for a positive outcome of the adequacy of the provisional SGR and for positive test results. Hence, awaiting the outcome of the check on the SGR adequacy shortly before the beginning of the tests next year, full-fledge preparations for the tests, are being continued.