eThekwini Municipality Umhlanga Stormwater Pier Submission for the Annual Branch Awards for Excellence in Civil Engineering and the Annual National Awards for the Most Outstanding Civil Engineering Achievement May 2007 Submission for the Annual Branch Awards for Excellence in Civil Engineering and the Annual National Awards for the Most Outstanding Civil Engineering Achievement May 2007 Project contributors Head Engineering: Adrian Peters Overall concept and Project Management: Coastal, Stormwater and Catchment Management Stormwater Design: Coastal, Stormwater and Catchment Management Deputy Head: Randeer Kasserchun Manager Rivers & Coastal: Godfrey Vella Project Manager & Engineers Representative: Dick Martin Structural Design: Structures Department Manager: Peter Fenton Architect: Andre Duvenage Electrical/Lighting Design: Rob Anderson Contractor: ICON/ESOR JV The project has been a particularly pleasurable one for all concerned not just because of technical interest but also because of the excellent team spirit that has prevailed at every stage of the job. Why the pier is the best project for the award From the outset the pier has been planned as a highly functional stormwater structure with strong aesthetic design elements to maintain the high standards of the Umhlanga promenade, as well as to minimize environmental impact on the very visible rock pools that give the area its unique character. inadequate capacity of main stormwater system of Umhlanga Rocks; a series of contracts commissioned to improve the system; two final stage contracts: a) construction of large underground box culvert ending at promenade and b) construction of outfall pier carrying stormwater discharge across the beach as far into the surf zone as possible. Context underground box culvert daylights just above the beach & continues over the beach as pier backbone; pier to extend approximately 85 metres to a deep-water channel for maximum dispersal; sometimes unsightly existing discharge outlet at Grannys Pool to be rerouted to new system; quality of the beach to be greatly improved, maintaining Umhlangas blue flag status. Context The Pier unlike any previously constructed in the region; 12m long spans to permit continuous public access along the beach; deck spans supported by single elliptical section columns founded on rectangular bases excavated and anchored into competent rock; at point of transition from underground culvert > pier, cross-section changes from conventional box to shallower boat hull shape; disguise of true function and visually less obtrusive. very aggressive marine salt-spray environment; special high-density 40Mpa concrete mix used to provide durability and long-term resistance to chloride penetration; all reinforcing galvanised for longest possible life for the structure. Concrete various specialist reports to ensure design suitability; Davies Lynn and Partners: detailed geotechnical investigation for the foundation design; CSIR commissioned to undertake study of wave loading on the columns and wave climate; latter report predicts highest waves to pass approximately 0,5 metres under the structure; confirmed by photographs taken during March 2007 equinox spring tide. Specialist reports aesthetics a very important design element; leading Durban Architect engaged to give 21st century styling; new technology low energy / high output light emitting diodes to be installed for illumination of the deck and superstructure; overhead lighting will be carried on curved fibreglass lighting masts giving a whale-bone theme; extensive use will be made of polymer concrete fittings and the pedestrian surface will be topped with coloured decorative screeds. Aesthetics two previous piers off the Durban beachfront constructed by Esor; both were founded in beach sand and consisted largely of pre-cast elements and little in situ concrete; new challenges of constructing a pier founded on rock; not a single pre-cast element. Falsework intricate architecturally pleasing design of concrete spans a nightmare for form-work designers/manufacturers; form-work designed in house and manufactured by the structural steel company Avellini Brothers according to the architects requirements. Formwork support of concrete structure during erection of the form-work and pouring of the concrete a challenge; temptation to support spans off the beach and underlying rock using conventional staging; elimination of risk of tidal action with box girder system supported off cantilever brackets tied to the columns; correct alternative during the extraordinarily high seas of the first weekend of April when the support-work was battered by giant waves. Box girder system concrete essential to aesthetics and dependant on formwork design for a common texture free from defects; formwork to be rigid and interlaced containing uniform curve of the boat hull shape; joint lines positioned to augment definition of the structure; rigidity put to the test by massive seas in early April to emerge unscathed; team approach: ultimate check prior to 1st pour carried out by architect to ensure final product met with vision. Concrete & aesthetics marine concrete developed by Contest Concrete Technology Services to a particular specification for the project; emphasis on achievement of high compressive strength 40Mpa (cubes crushed at over 50Mpa), low permeability & low percentage of voids; durability tests for oxygen permeability, chloride conductivity and sorptivity in addition to the usual cube tests. Special construction features: Concrete Mix Design concrete pumping most suitable for linear nature of structure extending from land into sea; compact static pump required since not enough working space on promenade for pump-truck and mixer trucks - cost also prohibitive; contractor located SEM concrete placer needing only a good supply of compressed air; after initial learning curve, concrete placement very efficient and tidy. Special construction features: Concrete pumped using SEM pump corrosion and spalling of reinforcing steel in a marine environment a great concern; cost of remedial work easily exceeds the original construction cost of the project; stainless steel derivatives considered but cost excessive so all reinforcing steel was galvanised. Special construction features: Galvanised reinforcment superstructure abuts on caisson 7m x 4m x approx. 5m providing additional torsional stability; caisson sunk to rock at depth of approx. 5 m, filled with compacted sand and capped with 750mm thick top slab; transition section of culvert feeding into outfall structure also fixed into caisson abutment. Special construction features: Caisson blasting not permitted so column bases (3.5m x 3m) excavated down through soft laminated layers of sandstone until competent rock is found; rock formation dips towards the sea so each successive base is founded at a deeper level than the previous one; last base excavation approx. 2 m deep. Special construction features: Excavation access to excavations, bases and columns dependent on tides and unfavourable wind and wave conditions; temporary cofferdam built around last base for more working time during the short low tide periods. Special construction features: Tidal conditions six reinforced concrete columns with bases 3.5m x 3m x 1m deep socketed into competent rock at 12 metre centres; most seaward column well into the tidal zone; stability of substructure units rely on passive rock anchors: 8 no. Y32 dowels raked at 1:4 and fixed 2m into the bedrock; columns elliptical in plan, approx. 2.5m x 1.25m with recessed reveal for mosaic detail. Special construction features: Substructure superstructure is fixed at caisson abutment and free to move on laminated elastomeric bearing pads seated in pairs on top of columns; chosen over mechanical bearings because of the harsh marine exposure; additional durability provided by laminating shims of 3CR12. Special construction features: Bearings side forms specially manufactured to fine tolerances for close-fitting joints and high quality off- shutter finish; after each pour, shutters coated with clear polyacrithane for protection against rust. Special construction features: Falsework a reinforced concrete double-box section comprising twin 2.8m x 1.6m voids to carry stormwater; for low flow, water channelled into one box and drained down the centre of the last column; 6 spans of 12m and 7.5m cantilevered viewing platform; based on bridge deck design methodology with obvious exclusion of internal cross-beams at the supports - a thickened rib cradling the structure. Special construction features: Deck & Superstructure eThekwini piers generally utilitarian, for discharge of stormwater, and for fishermen and surfers; design imperatives for the Umhlanga Pier inevitably more complex and challenging; prominent position at intersection of main entrance to Umhlangas beaches and Umhlanga Boulevard, with new Pearls development and Beverly Hills as backdrops more innovative and holistic design approach was inevitable. Architectural features functional double-box superstructure starting point and inspiration for development of three- dimensional design theme; intention not to be too literal but to have fun using marine and maritime references; at same time necessary to consider use of materials and finishes able to withstand ravages of very corrosive environment as well as theft and vandalism. Architectural features: Design concept elliptical lighting masts in durable glass reinforced polyester with weathered copper finish a subtle reference to skeleton of a large sea mammal; exaggerated vertical scale, tallest masts almost touching to give visitors a sense of enclosure; functional belly has shark-like mouth where stormwater discharges into sea, deck cantilevers some 6m beyond; one can see and hear water whilst standing on a large grating made from pultruded material. Architectural features: Design concept deck pattern also in marine theme: fibre-reinforced pigmented concrete paving and decorative mosaics; other maritime-inspired purpose-made deck elements such as handrail stanchions, manholes, electrical draw boxes, deck-edging components made from polymer-concrete; deck-edging components to have a fish scale finish. Architectural features: Design concept cutting-edge public lighting solutions to provide efficient, effective illumination; lower energy usage reduces levels of fossil fuels burned, reducing levels of air pollutants; research has shown commercial establishments consume 20% to 30% of their energy just for lighting; nearly half is wasted due to inadequate maintenance, obsolete equipment or inefficient use; facilities implementing energy efficient strategies can reduce energy use for lighting by up to 48%. Architectural features: Lighting with support of eThekwini Municipalitys Special Lighting Department, LED was selected. LED (light emitting diode) technology many years old, but in last 3 years achieved outputs high enough for pedestrian, decorative & automotive lighting; on-going research could lead to the output doubling every two years; efficiency of standard lighting systems matched & surpassed - correctly specified and installed LEDs up to 4 times more efficient. Architectural features: Lighting Piers LED lighting solution comprises mast-mounted white deck lighting & decorative blue lighting illuminating Pier belly & beach below; aesthetically pleasing & efficient installation needing no or little maintenance for at least 10 years; following table provides comparison between traditional and LED lighting solutions. Architectural features: Lighting Traditional DesignLED Solution Electrical Load8.1KW3.5KW Lamp Life10,000 burning hours50,000 burning hours DisposalGlass / MercurySilicon / Copper Running CostR11, 000 per yearR4, 800 per year Lamp Life7 years13 years % Electrical Load Transferred to Heat 75%5% The project is characterised by its aesthetic appeal, the high quality concrete finishes being achieved and the construction techniques adopted to keep work off the beach as much as possible. Other features: Excellence, ingenuity & innovation in engineering although tide conditions have proved challenging to say the least, work has never been allowed to slow down because of the effect of unpredictable conditions. Other features: Managerial competence in meeting the objectives of the project, including timeous completion and budget considerations during the project, regular clearing of the sites portion of the beach of foreign debris; a special effort to preserve marine life encountered, especially during excavation of the column bases. Other features: Responses to environmental concerns previously, publics only viewing opportunity was of sea creatures trapped in rock pools at low tide; an unexpected benefit of the Pier providing new views of completely different and constantly changing scenario of fish. Other features: Public interest & benefits, & public relations value, of the project the end.