Delivering industry-leading civil engineering solutions for four-and-a-half-decades and counting, Sorensen Civil Engineering has been shortlisted for not one but two 2022 Irish Construction Excellence Awards – a feat which underlines the Cork-headquartered company’s ability to meet, nay exceed, client expectations across a diverse range of project types.
While it is a notable achievement to be shortlisted for one Irish Construction Excellence (ICE) Award, being announced as a finalist in two different categories in the same year represents an outstanding industry endorsement.
For Sorensen Civil Engineering Ltd., it is particularly satisfying due to the diverse nature of the projects involved. As Marina Park Phase 1 and Youghal Eco Boardwalk are distinctly different in brief, scale and scope, together they demonstrate Sorensen’s excellent workmanship and ability to deliver a vast range of project types to the very highest civil engineering standards
Delivered for Cork City Council, Marina Park Phase 1 has been shortlisted in the Civil Engineering Under €10m category while Youghal Eco Boardwalk – for client Cork County Council – is one of four projects in contention for the Leisure or Tourism Under €10m category.
Marina Park Phase 1
Marina Park is a public open space in Cork’s South Docklands and is seen as a key economic driver and catalyst towards the regeneration of this historic area. The park covers some 32 hectares in total and the Marina Park Phase 1 project represented approximately six hectares of this.
The site features several protected structures, including the 1760s Navigation Wall, Páirc Uí Chaoimh stadium and the Atlantic Pond, with ingenuity of design and skill in construction prominent across several key features – most notably the use of polished concrete as a surface finish to some 6,200 square.metres of pedestrianised public realm in addition to the river front walkways and seating areas.
This represents a move away from the more normalised paved finishes, providing a product and finish which is not only cost effective and durable but sustainable as the material was sourced locally (rather than importing paving materials such as brick, slabs or granite). Other highlights of the project include the provision of a specialist jetted water feature and a cover structure for use as a Central Plaza, while the contamination of the existing soil structure required management of some 15,000 cubic metres of contaminated material.
The brief provided to Sorensen required the completion of the first phase of Marina Park, with works including clearing the site, construction of the 6,200 sq m public realm space, two bridge structures and various culverts, construction of the Central Plaza meeting place, and the design and installation of a bespoke jetted water feature, together with extensive planting and landscaping requirements.
The landscape and features were modelled extensively using 3D software and BIM tools to aid in the visualisation of the park during the design process. BIM was indeed fundamental in the approach to the design and construction of Marina Park Phase 1, assisting the way in which all parties on the project could both contribute to project data models and draw information from them, improving many functions, from checking compliance with building regulations, through design, co-ordination, cost estimating, work scheduling, fabrication and construction, through to operations, future maintenance and even decommissioning and demolition.
Commencement of the project coincided with start of the Covid-19 pandemic, resulting in two significant periods of suspension. Despite the obvious difficulties presented, the project was managed through a process of cooperation and partnership and was largely completed on time and within budget, with the adoption of some key value engineering approaches limiting the financial risk to both client and contractor.
Marina Park Phase 1 posed the ultimate challenge of mixing heavy civil engineering works and structures with high-end hard and soft landscaping parkland aesthetic finishes. Management of the excavations and removal of contaminated soils would provide the key challenge for both the environmental and commercial success of the project.
The existing soils on the Marina Park site consisted of both imported made ground and natural soils The made ground was approximately 500mm thick comprising brown and black sandy, gravelly clay. Cork City Council provided a waste classification and excavation plan for the imported materials which indicated the made ground consisted of hazardous and non-hazardous waste. Sorensen tested the soil against the UK Land Quality Management / Chartered Institute of Environmental Health (LQM / CIEH) S4ULs Human Health Risk Assessment to ascertain if material could be incorporated into the permanent works. The limits specified for parkland were used to determine the associated human health risk posed by leaving the imported materials onsite.
Existing ground that met the S4UL quality levels for parkland use was retained in landscaped areas on-site and generally covered with imported Class 2C granular materials. Meanwhile, the made ground that exceeded the S4UL limits was placed beneath the paved areas and overlain by a layer of geotextile, a layer of inert Class 2C granular fill and finally the paved structure. Additionally, a blended mix of existing soils and imported Class C2 material was used as fill under roads and the raft foundation for the new building. The environmental benefit of utilising the existing contaminated soils on-site was enormous and saved the need to remove 15,000m3 off-site.
Placing of concrete to achieve the breath-taking finish to the Central Plaza floor represented another major success of Marina Park Phase 1. The project team carried out extensive research on the best methods of achieving the desirable finish on the exposed aggregate plaza floor. This research included test panels on-site and discussions with concrete specialists on how to achieve a top-class finish.
The challenge was to achieve the required strength in the slab through vibrating whilst retaining the coarse aggregates at the top of the concrete slab in order to achieve the desired exposed aggregate finish following grinding and polishing. The team developed a method of achieving the strength and finish by installing a plastic membrane between the subbase and the concrete slab, thus preventing the loss of moister from the concrete slab mix.
Furthermore, during site trials, they also developed a split slab-pouring sequence. The lower slab (1st 100mm) was poured and vibrated to achieve its desired strength and prevent cracking and the top layer (2nd 100mm) was poured immediately afterwards without vibration, which allowed the coarse aggregate required to achieve the finish to remain at the top of the finished slab level.
Sorensen also achieved outstanding results in terms of achieving and maintaining the programme during a global pandemic. The challenge of constructing a civil/structure/landscape project of this complexity in any twelve-month period is already significant, taking into consideration weather, location (flood plain) and the planting and growing seasons – but the arrival of Covid-19 to Ireland caused two extended industry lockdowns and also resulted in a massive shortage of construction materials. (By its nature and design, Marina Park required the procurement and delivery of material from China, Portugal and the UK.) Careful planning of the procurement of materials was key and Sorensen’s adaptable and proactive approach to the procurement process during the first shutdown was a key factor in the project’s success.
Mark Snow, who was project manager on Marina Park Phase 1, was delighted to see the project shortlisted for an ICE Award: “It’s fantastic. These are prestigious awards and when you look at the other wonderful projects shortlisted in that category, you can see that the competition is strong and it’s an achievement just to make the shortlist. To be considered in that company is humbling. Myself and the project team and the management team at Sorensen are all very proud.
“We knew early on from the level of detail and the level of quality going into the project that it was special. When we picked up the drawings, we knew it was going to be unique. The level of thought and work that went into it was exceptional. Between our management team and site team, we reached very high standards on Marina Park, with a lot of outstanding features included.”
On any civil/structure/landscape project, the finished works above ground are the standards the public will form their critical opinions on and public feedback will determine the success of the project for all involved in its concept and execution. For Marina Park Phase 1, the water feature, polished concrete plaza, elevated timber boardwalk, landscaping, meandering stream and the Central Hall Plaza are all standout features which individually and collectively define this project.
“The public eye won’t fully appreciate the work that went into it above and below the surface, from the landscaping to the concrete works, the water feature and the paving installation, the surfacing works, etc., but everybody involved in the project excelled,” Mark continues, “From the design team [Okra Landscape Architects] and the vision of the client to the capable and confident Sorensen crew, and our competent subcontractors, it was very much a collaborative approach from day one.”
While literally every aspect of Marina Park Phase 1 is exceptional, the project manager is particularly proud of the aforementioned imaginative and striking surface finish in the 6,200 sq. m. public realm space. “The exposed aggregate finish of the concrete plaza forms the centre point of the park,” he reveals. “We had to come up with a methodology to complete the pour in the best manner to facilitate the desired finish, with no cracking in the exposed concrete.
“We carried out extensive research in advance before decided to compete the pour in two layers of 100mm instead of one pour, vibrating the bottom half but not the top one. A lot of work and detail went into pouring that slab. There is only one other area in Ireland – also in Cork, but on a much smaller scale – where that type of slab is used. We managed to achieve a nice uniform finish throughout. In keeping with the project as a whole, this was a massive challenge and also a massive success.”
Youghal Eco Boardwalk
Youghal Eco-Boardwalk Phase 2, meanwhile, comprised the construction of a new ‘Eco Boardwalk’ on the seaward side of the Ballyvergan Dunes. The development entails the erection of a 1.1km stretch of 2,300mm wide elevated composite structural steel / timber decking boardwalk and ancillary works along the beach from the Claycastle car park to the Quality Hotel at Redbarn. Works were carried out in an environmentally-sensitive environment and this sustainable timber designed boardwalk now forms part of the longest seafront boardwalk in Ireland.
All works were carried out in a marine/tidal environment, the design focussed on sustainable materials, products, methodologies yet it had to be suitably robust to withstand constant attack from the adjacent sea. Again, the project was completed during the course of the Covid-19 pandemic, but was nevertheless largely completed on time and within budget, with deliveries negotiated from the UK and West Africa to avoid delaying the project.
The brief required the completion of the 1.1km Eco Boardwalk, including clearing the site, initial SI, installation of six test piles, installation of 1,000 220mm diameter x 7.5m to 9.5m long CHS driven piles, construction of steel substructure, timber decking, timber steps, in-situ RC steps, footpaths, construction of an RC marine slipway, fencing, supply and installation of changing huts and public seating, installation of two bike stands, installation of rock armour and re-profiling of the beach along the boardwalk.
Sorensen collaborated with the design team to carry out a series of test piles to establish the depth to competent rock. Once the test piles were complete, Sorensen carried out Static Tension Tests on the piles to calculate the pile displacement in millimetres under upward loading. Dynamic Tests were also carried out on the trial piles to determine the ultimate bearing capacity of the piles. This process provided the client with great comfort in the suitability of their design.
Sorensen proposed an alternative rare specialist hardwood called Lophira alata (known as Ekki) for the boardwalk decking. This material was sourced in Cameroon and is known locally as ‘Red Ironwood’. Ekki is amongst the hardest and densest timbers in the world. The maintenance requirements for Ekki are significantly lower than alternative hardwoods given its hard-wearing and durability characteristics. Thus, it provides for an exceptionally high-quality and robust finish to the boardwalk.
Sorensen identified the construction of the in-situ RC steps within the tidal zone and below the water table as a challenge. They proposed an alternative bespoke precast unit with a lightweight hollow core design. These precast units were constructed in a casting yard in Youghal, with a hollow centre to provide a suitably light unit that could be lifted into position along the beach. The main contractor then mobilised their 50-tonne CAT tracked excavator to lift the RC steps into position along the beach. Once the precast units were in place, the hollow centre were filled with grout to add the necessary weight.
A severe storm struck the partially-completed boardwalk in November, 2020, washing away a significant quantity of ground from the area in front of it. Subsequently, there was a large vertical drop from the boardwalk edge to the beach below. Sorensen provided the client with a simple solution, regrading the beach with their GPS machine controlled Komatsu D85 dozer, the designer having provided a 3D design of the proposed finished levels of the beach. This solution also provided for a safer boardwalk for the public to use in future.
Securing the site from the public was particularly challenging as it is linear along a very busy public beach. A robust temporary fence was erected along the seaward side of the boardwalk to segregate the public from plant and equipment. This fence was removed and reinstated numerous times during inclement weather events. Meanwhile, all deliveries to and from a nearby compound were completed before 6am every day to avoid construction traffic interfacing with public walkers / joggers etc. at site access points.
The client carried out a safety audit on the partially completed boardwalk. It was decided that given the changing levels in the beach and the presence of rock armour, a new handrail was to be designed and installed in certain sections of the boardwalk for additional safety. Sorensen collaborated with the designer and their local fabrication workshop to design, supply and install a stainless steel handrail that blends in seamlessly with the design of the boardwalk.
Constructing a 70m long x 15m wide RC slipway below MWLS level on a beach was challenging. Sorensen designed and installed a temporary cofferdam that permitted the works to take place in a dry and safe environment. Care was taken during the dewatering operations at the cofferdam to ensure the pumped water was desilted prior to returning it back to the adjacent estuary. The site team liaised and consulted with Inland Fisheries Ireland and National Parks and Wildlife Services during these works.
The biggest success of this project is the quality of the finish to the timber deck work. The specialist carpenter subcontractor enlisted has particular expertise working with hardwoods and the timber work was ongoing on three fronts, namely placing the joist framework, placing the boardwalk deck boards and completing the toe boars and timber steps. The three fronts allowed Sorensen to complete all of the works behind the timber gangs on a ‘finish as you go’ basis.
Sorensen Civil Engineering’s experienced site team collaborated with their local concrete provider to ensure that the concrete could be successfully delivered to fill the core of the precast concrete steps. Obvious challenges included ensuring the concrete mix was suitable for the saline tidal conditions, avoiding the lorry getting stuck in the soft sand and ensuring the tide didn’t affect concrete pours. Vehicular access was only permitted at one end of the project, so all construction vehicles were required to negotiate up to 1.1km of beach terrain around ever-changing tides. The team worked around the clock to ensure lorries could travel on the dense, wet sand at low tide times.
The logistics of handling the 9.5m long CHS piles including taking delivery, storing, delivering to the pile location, lifting the pile plumb into place, driving the pile to a set, cutting the pile and testing the pile were challenging, but the experienced Sorensen team self-performed the piling works using their CAT 328C excavator and new Movax SG60v Vibro Hammer.
They devised a suitable bespoke piling frame and system of delivering sufficient numbers of piles before 6am, working their way through the pairs of piles during the day, ensuring every pile was set before moving to the next one. Additionally, they partnered with a local steel fabrication specialist to supply and install the steel framework that supports the timber boardwalk deck. This steelwork is an integral part of the boardwalk design that ensures the boardwalk is sufficiently robust to withstand storm surges during the winter.
The critical aspect of this element of the works was accurately measuring the as-built pile locations to allow the steel fabrications to commence. The dimension of every steel cross-brace associated with the 1,000 piles was different, yet the coordination between Sorensen and their supply chain ensured it all went together like a jigsaw. Having a local partner located in Youghal de-risked this process. The piles could be surveyed every morning by the fabrication specialist and the Sorensen site engineer, permitting a constant flow of fabrication, galvanising and installation works each day.
An experienced site delivery team worked closely with all stakeholders, including the public, to ensure that works were competed safely and efficiently. Noise and dust monitoring was carried out to ensure all levels stayed below allowable levels for this urban area.
The project was delivered on a very busy beach in a busy tourist town. This was exacerbated by the effects of the public health lockdown, with people just wanting to get out and walk the beach. Subsequently, Sorensen implemented robust mitigation measures to ensure the safety of the general public during the works. A flagman was in position at the entrance to the site to ensure 100% segregation of construction traffic from the public.
As the timing of the in-situ concrete works was dependent on low tides, there were times when concrete pours coincided with peak pedestrian traffic times on the beach. Each occasion was risk assessed during the works; if the weather was fine and crowds were expected then the pour was postponed in the interest of public safety. On other occasions, additional fencing, signage and flagmen were deployed at strategic locations around the site and the pour continued safely.
The project was delivered to the highest standards in safety with no lost time incidents or accidents during the 11,200 completed man hours. Considering the close interface with the public on the adjacent beach during the summer months and the largescale civil engineering operation undertaken, this represented a significant achievement.
The quality of the timber craftsmanship on the finished boardwalk greatly exceeds what was expected by all parties. The joints, cuts and details of the timberwork is exemplary. Sorensen’s management of the 1,000 CHS piles was a major success. The piles are all accurately installed to the required set and within tolerances. A significant challenge at the outset was keeping these huge piles in full control during all stages of installation, i.e. receiving delivery, offloading, storing, reloading, transport into a busy public beach, offloading on a public beach, positioning, pile driving and cutting. This was successfully achieved for 1,000 individual piles, without incident. Furthermore, Sorensen maintained the control over each pile that was necessary to achieve the accuracy of the final pile head position along the boardwalk. This permitted the steel fabricator to maintain consistency in the member sizes of the galvanised steel substructure.
Sourcing an exceptionally talented timber specialist willing to go above and beyond the brief in delivering a high-quality finish on the boardwalk represented a big win on this project. The team’s attention to detail and their tenacity to work through the months of inclement weather on their knees on the boardwalk was admirable. Their dedication resulted in the remarkably high-quality finish we see today.
Youghal Eco Boardwalk enhances the natural heritage of the surrounding scenic area, facilitates easy access for the elderly as well as people with limited mobility, wheelchair users and those with pushchairs. It is part of the wider National Coastal Walking Route and is in line with the government’s National Outdoor Recreation Strategy, bringing huge benefits to the community from both a health and economic perspective.
The buy-in and interest from locals during the course of the works informed project manager Eoghan Deane that Youghal Eco Boardwalk was not only a landmark project but a well-received one: “From the get-go, the public were very interested in finding out when was the boardwalk going to be opened and we realised from the buy-in of locals that this was a project that was really going to benefit the community. People are delighted to have that extra facility in place. There was great feedback from the public during construction and indeed since the project was finished, so it has been very well received and that is rewarding to us.”
While the first Covid-enforced lockdown impacted the programme slightly, Sorensen were generally able to continue working relatively-uninterrupted on the boardwalk. “We were shut down for four weeks early on, but were then allowed to continue on,” Eoghan reflects. “We got dispensation from Cork County Council to allow one crew at a time on site and we had the carpentry crew working away. There was no additional risk involved as it’s a family business and they were all members of one family anyway.”
Touching on some of the challenges presented, Eoghan continues: “From an engineering point of view, positioning the 1,000 CHS piles in line with one another and so that they finish continuously at a certain height was a challenge. The quality of the timber deck finish is second to none. We employed highly-skilled 2nd-fix carpenters, who went above and beyond what was expected in terms of detail and finish. The boards are positioned exactly 3.5mm away from one another, parallel to one another, all level, and each is sanded to make sure there are no sharp edges or sudden turns. The finish features very precise, exactly straight lines down to the last millimetre. Even though we come from a civil engineering background, it is important to us to make sure that everything is perfect to the last detail.
“There are up to 10,000 boards in total and each has eight screws that had to be lined up individually. Everything is uniform and parallel and positioned in the exact right place. Because of the unforgiving toughness of the timber, each screw hole had to be drilled three times – a 1mm pilot hole, then a 3mm pilot hole, followed by a countersunk hole. So there were four operations to install each screw.
“This was a slow and painful process and we incurred a lot of burn-out of equipment. It’s really difficult to fathom just how hard that timber – which is ideal for use in a marine environment – was. We counted that the chippies broke around 1,000 drill bits. Ekki is extremely hard, with no forgiveness in it whatsoever. It’s so strong and dense that it broke €5,000 worth of cutting and drilling equipment!
“As there is farmland to the back of the boardwalk, we had to build a slipway so that the farmer could gain full access to his property, and get his tractor up and across the boardwalk. We came up with a novel structure and design to ensure that there was no risk of the tide washing it away. It was challenging completing this 70 x 50m permanent concrete structure in a tidal zone, where we had a limited four-hour window to pour the concrete during low tide, but we came up with a tailor-made solution which is to everybody’s satisfaction.”
As for seeing Youghal Eco Boardwalk shortlisted as a finalist at this year’s Irish Construction Excellence Awards, Eoghan concludes: “We’re delighted to be part of these awards. This is a community project, which everybody can use and avail of, from children to the elderly. We are very proud to have worked on something which is so valuable to the local community.
“Huge credit has to go to Cork County Council for having the vision to provide this facility and to get the funding and see it through. We’ve worked extensively with Cork County Council down through the years – and also with Cork City Council and Irish Water, to mention a couple of others – and they are an excellent client.”
Established in 1977, Sorensen Civil Engineering Ltd. is a multi-disciplined construction company that has grown and developed over the years to become one of Ireland’s leaders in the sector. The company has a proven track record in delivering projects through every stage from concept, planning, design and budgeting through to construction.
They have completed a vast array of projects down through the decades for a host of clients including local authorities in Cork, Kerry, Clare, Waterford, Limerick, Tipperary and Dublin, the ESB, OPW, IDA Ireland, the HSE, the Department of Education, Transport Infrastructure Ireland, Dairygold, Spar, Centra and Super Valu. Going forward, they are fully committed to working in collaboration with clients and their professional teams to achieve optimal construction solutions and to deliver the best value when doing so.
Sorensen Civil Engineering Ltd.,
Forge Hill Cross,
Kinsale Road,
Cork.
Tel: 021 4968917
Email: [email protected]
Web: sorensen.ie
This article was published in Building Ireland Magazine, September 2022, Vol 8 No 9
Sorensen Civil Engineering Ltd.
