At Hartigan we recognise that each project is different and requires an individual approach. The object and emphasis on every project is to engineer a solution which achieves the clients brief while being cost effective. Our clients benefit from our comprehensive services. We take the projects from initial concept through design, detailing, to completion. With our dedicated personal service and high level of engineering skill
s, along with access to specialist consultants ensure that our clients’ desires are achieved and regularly exceeded.
For 35 years our dedicated employees have been offering a unique skill-set combining an understanding of traditional building techniques and materials, with access to state-of-the-art technology. We engage high calibre, highly qualified personnel; invest in training and maintain up-to-date computer systems to aid design, modelling, drafting and communications.
We have a broad client base with clients from both the private and public sector. We have participated in some of the largest and most prestigious projects on the island, public buildings, utility providers, infrastructure, social housing, schools, sports facilities, commercial developments, welfare, hospitality, and private residences. We also provide a personal and professional service to smaller domestic projects undertaking new build, extensions, remedial works, modifications and works to historic structures. Whatever the project, whatever the size; we have the team who can deliver with professionalism and integrity to bring your vision to fruition.
We strive to provide a high level of quality and efficiency and have completed an extensive quality assurance programme in which we developed an ISO9001 system which was certified by the British Assessment Bureau (BAB) in early 2019. This assessment shows that we meet all of the requirements of the ISO9001 system. Due to the certification provided by BAB we are able to show the UKAS crown as a further example of the quality system.
We also take our business and client security seriously and have obtained certification for a Cyber Essential approved company. This certification shows that our systems are extremely robust in relation to cyber security. As part of the preparation for this and for the continual accreditation all Hartigan staff undergo regular cyber security training provided by a third party.
This extensive project entails construction of a new secondary school for the Island, replacing the existing facility on a green field site. The development comprises the main secondary school building, a sports centre, external all weather multiuse sports pitches, and associated infrastructure including services and car-parking.
The project was designed using the latest design and building modelling technology, aiming to deliver the project as a BIM Level 2. The structure of the building was modelled 3-dimensionally and coordinated with the building fabric, finishes and building services. This method allows potential clashes to be identified during the design phase of the project, minimising the risk of expensive changes during construction.
Hartigan’s involvement in the project began during the pre-planning feasibility phase at the end of 2014, through to completion in time for the new school term to begin in September 2020.
Our Civil and Structural Engineering Team advised on the need for intrusive geotechnical site investigation, prepared phase 2 contamination desk studies for planning purposes, conducted flood risk assessments on the site, and provided full structural engineering design services.
The building is of steel frame construction, with composite concrete floor slabs and steel beams. This form of construction was selected to provide maximum clear spans, allowing flexibility in arrangements of internal walls depending on future needs, and a relatively light-weight structure.
Challenges to the project included initial planning refusal, a difficult compulsory purchase process and budgetary constraints. These required the Design and Construction Team to work closely together to value engineer the design within the Client’s budget without compromising quality, and against an ever-looming completion date of Summer 2020.
Hartigan’s Structural and Civil Engineering team are proud to have met the challenge head on and delivered construction information for primary sub-structure and super-structure to allow the steel frame of the building to be complete 2 months ahead of programme.
The owners of Sundowner decided to enhance their property by extending the existing balcony and giving it a modern appearance by adding a free-standing glazed balustrading. The design called for a cantilevered balcony deck above parking hardstanding and frameless glazing; Hartigan cooperated closely with the Contractor to establish the most time and cost-effective engineering solutions.
The existing balcony is supported by two load-bearing walls and a reinforced concrete beam with an upstand, which led to its demolition as the level of the new balcony was to be the same as the existing one.
Trial hole inspection verified that the foundations are suitable for the new steel frame, no signs of structural defects or distress.
The primary steel structure are two beams ‘running’ across the balcony, both existing and new extension, connected to the existing external wall of the property. Acting as a secondary frame, the beams around the balcony perimeter are connected to the existing load-bearing walls.
Contemporary design, good workmanship and efficient teamwork resulted in successful delivery of this project.
Fort William is one of a series of defensive fortifications that was constructed during the 18th century to protect against French invasion. It was converted into a private residence during the latter half of the 20th century.
The current owners decided to create a modern two-storey extension to the east, incorporating a spacious lounge, kitchen and dining area enclosed in a glass walled building designed to give the appearance of floating above the walls of the listed fortress.
Hartigan’s scope of works included design and detailing of the steel frame structure, supporting the glass panels. The frame needed to be sufficiently stiff to prevent movement to the glass without detracting from the aesthetic of the building.
The project was challenged by limited access. Transporting the steel frame and glass panels across the existing drawbridge and through the existing gate of the fortress was not easy. Close cooperation between the Architect, Structural Engineer and Contractor led to an exceptional project.
Hartigan were extremely pleased to provide Mechanical and Electrical engineering services on this prestigious project for Jersey Society for Prevention of Cruelty to Animals (JSPCA).
The work was undertaken as part of Jersey Construction Council charitable fund, The Brick Foundation, a charity set up by the local construction industry specialists with the aim of putting something back into the community.
JSPCA’s commitment is to maximise the value and the potential of their St Saviours Road site, for the site to be sustainable for many years into the future. Whilst in no way compromising on the needs of the animals the existing old kennel blocks has been turned into a bespoke Small Animal Centre. This building will clear the way for all the future projects that the JSPCA has in mind in order to achieve these goals. Hartigan are proud to have supported this commitment by the JSPCA.
The Small Animal Centre houses animals such as rabbits, reptiles and kittens. The centre contains purpose-built units to suit the specific needs of each species.
The work required new efficient LED lighting and emergency lighting, small power and distribution, fire detection and alarm system, hot & cold water distribution with sanitaryware, ventilation and user-controlled heating systems.
Belmont Court is a part of larger development which endeavours to transform a discontinued brewery site into much needed housing accommodation. A block of 15 one, two and three-bedroom apartments provides modern living accommodation and contributed to regeneration of the North of St Helier.
Hartigan were appointed as part of the design team to provide the design and detail of the building services.
Hartigan are very conscious of the need to provide systems which are energy efficient and cost-effective. On this project we incorporated in the design:
Also in the design, electronically operated window actuators were provided in a number of apartments to assist people with disability.
Belmont Court is a part of larger development which endeavours to transform a discontinued brewery site into much needed housing accommodation. A block of 15 one, two and three-bedroom apartments provides modern living accommodation and contributed to regeneration of the North of St Helier.
Following demolition of the boiler house, Hartigan were appointed as Consultant Civil and Structural Engineers for the development.
Hartigan’s duties included the procurement of geotechnical and geo-environmental site investigations, the production of interpretative geotechnical reports, below ground drainage design, together with design for the new structure.
The heavily glazed colonnade to the east façade of the building, led to an innovative concrete framed design of the structure.
Challenges faced on site during construction included the presence of a substantial foundation to the existing chimney stack to the boiler house. This required the pile and ground beam sub-structure to be carefully designed to avoid the need to break out this structure.
The former Elizabeth Terminal Restaurant has been completely refurbished, as a joint venture between Ports of Jersey and the Casual Dining Group. The restaurant provides a modern all-day dinery. Hartigan were engaged to provide structural engineering services in relation to all the aspects of the new establishment.
With all projects where we are working in existing building, the first step is to check the suitability of the existing building to accommodate the changes. Beyond this, we carried out detailed design checks on the ground slab and foundation, multi-storey metal studwork, framing to carry plant within the ceiling space, new mezzanine floor, new offices, kitchen and bar facilities.
The work was completed in July 2019.
Chambers pub has been a well-known venue on the Island since its opening in 1994 and Hartigan were pleased to be involved in its refurbishment.
As is the case with buildings of considerable age, numerous alterations had been undertaken over its life, and Hartigan’s engineers faced various challenges in adopting modern design to fit with the constraints of existing structure. Due to the premises still operating during the design stage, the investigation works necessary to assess the suitability of the existing walls and foundations were undertaken once the works commenced. This required the engineers to maintain close connection with the contractor, and to respond quickly to queries or findings on site.
The refurbishment works included various internal alterations, new stage structure, lowering of existing ground floor to the back of the restaurant and night club, new mezzanine structure of steel and timber, new mono-spine steel staircase and new opening in existing large granite wall. Hartigan’s engineers provided structural design and drawings for all those elements. We were also involved in extensive and complex temporary works, providing support of the new frame and existing granite walls.
We are delighted to see that Chambers refurbishment project was successfully completed.
Hartigan were very pleased and excited to provide Civil, Structural, Environmental, Mechanical and Electrical engineering services on this prestigious project. Jacksons are a premier car dealership and the car manufacturers are known world-wide; we knew the standards required were going to be very high. This complex project comprised construction of two new showrooms, a large extension to the existing service centre, refurbishment of the office accommodation and valeting facilities.
Initial stages included assessment of the site and consideration of potential environmental aspects of this type of commercial facility.
The building design called for large open spans with fully glazed façades, and a high parapet to display the signage. This is complex structurally as deflection must be limited to fit with the ridged nature of the glazing, and other factors such as wind load had to be taken into consideration.
Due to different ground conditions across the site and between the buildings, a combination of pad foundations and ground slabs was developed. A steel frame to the service centre was installed as a large span portal frame to fit with the existing building. The showrooms required wide, open, well-lit spaces. Steel frames were used to accommodate substantial glazed side walls, together with Vierendeel girders for the roof to keep the roof below the parapet.
The mechanical and electrical services needed close attention to detail to meet with the manufacture’s requirements. The heating and cooling is provided by air conditioning, and Hartigan’s engineers also designed bespoke lighting system to suit supply the lighting levels required by the individual manufactures.
The owners noticed cracking to the corner of the property and engaged Hartigan to inspect and determine the cause of the defects. A subsequent claim was registered with the insurers for remedial works following building subsidence. Hartigan’s involvement in the project encompassed site investigation, design of remedial solutions and contract administration.
The major difficulty in undertaking remedial underpinning were the site conditions, with large voids under the foundations as well as large boulders. The remedial solution comprised installation of micro piles drilled into the soil and fitting pile caps, ground beam and concrete needles which extended under the wall to support the building. Internally, piles and concrete needles were also installed in the kitchen. Protective screens were provided which allowed the owners to continue using the kitchen and to ensure the working site was kept isolated from the occupied areas.
The piling contractor had to cope with restricted space and installed the piles by way of a rig fixed to an excavator arm, a method they developed from installing rock anchors on embankments. A close cooperation between the main contractor and piling contractor ensured that the project was delivered on time and within the budget.
The project consisted of the redevelopment of an existing derelict school campus site to construct 187 units of residential accommodation divided into 6 apartment blocks.
The redevelopment of the site faced a number of challenges that are common to the Island, including steep topography, varying ground conditions, and close proximity to adjacent properties including Janvrin School. Moreover, the scheme had to be developed around the need to incorporate and preserve the original 19th Century, listed Ladies College building, designed by Adolphus Curry.
Hartigan’s involvement began at initial concept stage mid-2012, and we continued to work with the Client, project Architect and subsequently the design-and-build Contractor to completion early in 2019.
Our structural engineering team, advised on the need for geotechnical site investigations, and provided full structural engineering design services from feasibility through to detailed design. Our civil engineers advised on site drainage, road and hardstanding design, together with temporary rock stabilisation during excavation works.
Our specialist Historic Building Conservation team, provided advice on the conversion, repair and preservation of the retained fabric of the listed building, and assisted the Architect in agreeing the extent of the scheme with the Planning Department.
The new build apartments are of traditional construction, with in-situ reinforced concrete floor slabs supported on load-bearing masonry walls. A landscaped communal podium area forms the ground floor, beneath which semi-basement car-parking and stores are located.
Ground conditions and proposed building finished floor levels varied across the site, giving extremes of foundation solutions. Block 4 requiring an 8-metre excavation through solid rock, and Block 1 requiring piled foundations, some 10 metres in length, through superficial deposits to reach bedrock.
The internal structure of the retained listed building had deteriorated significantly over a number of years as a result of dry and wet rot, and required wholesale replacement of internal floors, and roofs, together with repair to the masonry façades. We worked closely with the design-and-build Contractor to agree a construction methodology that minimised the temporary works required, while allowing the build to meet the Client’s programme in a safe manner.
Following a cliff-face collapse in March 2016 significant works were required to ensure the stability of the slope and to ensure the safety of the residents of Cheval Roc Nursing Home. The north-west wing, which was in a risk of collapse following the land slide had to be demolished and rebuilt.
Hartigan have been involved in the project from the initial stages. After the geotechnical survey we worked with a specialist supplier to provide a suitable netting for the slope, a combination netting was chosen which contained both the structural support and the erosion control. Stabilisation works, carried out by Geomarine, were undertaken to extremely stringent Health & Safety and quality standards. Multiple tests were carried out daily on the grout used for installing soil nails, the nails and piles.
Hartigan were requested to develop a suitable fencing system which would allow access for maintenance around the buildings, but prevent accidental falls. We worked with a specialist to modify an existing temporary system of mesh and posts, to make it suitable as a permanent solution in a marine environment.
The north-west residential building was constructed of structurally insulated panels, which allowed the construction of the building, including roof, within two weeks. Many of the windows were recovered during demolition and reused; this not only saved money for the client but is also beneficial to the environment.
The project was completed on time and budget, to the total satisfaction by the client.
Redevelopment of Bellozanne site comprise construction of sewage treatment plant, which required extensive excavation and stabilisation of the surrounding rocky slopes. During excavation of the base, a substantial section of highly contaminated materials was identified.
Hartigan were requested to establish, oversee and manage appropriate laboratory testing of the material in order to determine if direct disposal was possible. The results indicated that a very high level of hydrocarbons was present in the excavated material, which makes direct disposal impossible. Hartigan’s environmental team developed a remediation strategy that used chemically dosed windrows to reduce the levels of hydrocarbons in the material. The process of repeated dosing and turning of the material reduced the contaminants from several times the disposal limits to within the limits in only a few months. Hartigan undertook final assessment and reported that the material was acceptable for disposal and reuse at the La Collette facility.
Harbour Warehouses are a range of 5 No historic granite buildings dating from 1899. They house Jersey Maritime Museum and workshop, and harbour facilities. The buildings are constructed of thick stone walls, with long-spanning queen post roof trusses and natural slate roofs coverings.
In 2017 Hartigan’s engineers carried out a condition survey of the truss timbers and the roof structure. The survey identified deterioration of the roof coverings, which required extensive repair and replacement works. Hartigan prepared specifications and structural details for re-roofing of all warehouses, including lead lining to cast-iron valley gutters and verge secret gutters.
Hartigan prepared tender and contract documentation and acted as contract administration on behalf of Ports of Jersey.
The project consisted of the replacement of an existing concrete batching plant, with a new state of the art facility at Granite Products’ La Gigoulande Quarry. In addition to the works connected with the new batching plant, Hartigan also designed new substation and laboratory/control room building, new hard-standings and below ground drainage.
The new plant was fabricated in Turkey and the logistics of transport made the time of the delivery and thus project programme critical. The challenges included adjusting the levels of the proposed site to accommodate the pre-fabricated plant equipment and stabilisation of a steep slope and constructing permanent works in close proximity to a vulnerable rock face. The plant operations necessitated the works to be planned to avoid an existing high voltage electricity cable.
The gravity retaining wall was designed to be constructed using large pre-cast concrete units which interlocked in a similar manner to Lego blocks, which allowed flexibility over an uneven ground. The slope was stabilised using a geotextile anti erosion matting, which over time will grow over and give a natural appearance to the slope.
The project was designed to be as environmentally-friendly as possible: the pre-cast interlocking blocks were manufactured on site, and a wedge pit was designed to capture all surface water on the site for re-cycling and re-use in the batching process.
The control of Health and Safety, both on site and in terms of design was paramount, with the plant being subject to stringent quarry safety regulations. Health and Safety was overseen by the Client’s Health and Safety Project Coordinator, with regular audits carried out during the site works.
The project was designed to be as environmentally-friendly as possible: the blocks were effectively formed from “waste” concrete, that was returned to the quarry following concrete pours on construction sites, and a wedge pit was designed to capture all surface water on the site for re-cycling and re-use in the batching process.
Works were completed on time and on budget, allowing the new plant to be commissioned at the end of January 2018, and allowing the Granite Products plant to keep producing the materials for the Construction Industry of the Island.
The proposed works to the pressoir building at Les Cotils Farm comprised conversion of the cider press barn into self-catering holiday accommodation. Originally an agricultural outbuilding in which apples were pressed to make cider, the building had been used for many years as a ground floor workshop with first floor storage. In keeping with the National Trust’s ethos for conservation best practice, structural repairs were undertaken to retain as much historic material as possible, whilst respecting the evolution of the building. where defective material had to be replaced, the repairs utilised materials faithful to the original construction of the building, based on documentary evidence.
At the outset Hartigan undertook a structural survey, comprising measurement and condition survey.
The structure required extensive restoration work, including repairs to floors and roof, modification to staircase and reconstruction of south-facing brick façade on new foundation. Hartigan’s engineers prepared design and drawings for structural works and specifications for structural repairs.
The Snow Hill Car Park project comprised various element of engineering works undertaken between 2015 and 2019. At the outset, Hartigan were employed to undertake a survey of an avalanche canopy above the car parking spaces to the west of the site. The canopy was in a precarious state in places and in need of repair. Hartigan’s engineers undertook a detailed survey of the canopy. During the inspection of the canopy, it was found that also the brick and block supporting columns and the rock face in between them are in in need of remedial works. Hartigan also undertook a risk assessment of the rock outcrops beneath the canopy and this identified several areas that needed stabilisation works.
For all the elements of work Hartigan’s engineers prepared tender documentation including specification for repair/replacement works and necessary technical drawings. Following the appointment of the contractor, Hartigan’s engineers managed the contract and supervised the works.
Hartigan was also requested to assess the risk of collapse of historic granite blocks which make up part of Fort Regent. A series of complex internal and external surveys were carried out, including geometric survey. The challenges involved in the surveying works included limited access, working out of hours and cooperation with multiple stakeholders. The assessment of this identified that whilst the blocks look like there are tipping over, they are currently stable and in good condition.
Hartigan were engaged by Jersey Electricity to assist them in providing a solution to installing a lining to the rock face at the back of the bunded area in which the fuel storage tanks are housed.
Initially a method of shotcreting was the favoured option. Hartigan prepared specifications and sought tenders for this option. Tenders were received as compliant bids. One of the tenderers offered an alternative bid – the use of concrete canvas. Considerable investigation was carried out, Hartigan worked closely with Geomarine, the specialist local contractor, and the manufacturer of the product to ensure it is suitable. The product comprises of a flexible membrane which contains a cementitious mix which hardens on hydration. The product is easy to handle and is suitable for areas where access is difficult.
The works had to be carefully planned as the site was fully operational during the installation of the canvas, and the contractor had to be aware of high voltage cables in the vicinity. The works took place in confined spaces, amongst oil tanks and gas-oil pipes and within the 3.8m high concrete bund wall surrounding the oil tanks. The contractor provided protection to all supply pipes, cables, utilities and services as any damage caused to pipes and tanks could have caused oil to leak from the large oil storage tanks and flood the bunded area.
To our knowledge this was the first case of installing such a system in Jersey and it was delivered in a timely manner and to the Client’s satisfaction.
Some buildings comprising Normans depot had originally been constructed over a backfilled former brick pit. This type of strata may be subject to movement and result of building subsidence, which happened to the warehouse in the timber yard.
After a walkover survey it was determined that further, more intrusive. investigation will be required in order to establish an appropriate method of remedial works. Hartigan have prepared a specification for the investigation and obtained quotations. At this point in time the intrusive investigation is being arranged and are scheduled for summer 2019.
Hartigan were asked to undertake a comprehensive structural assessment of the building before sale. In the first instance, a desk study and visual assessment were carried out, which were followed by a flood risk assessment requested by the client. This process comprised surveying of the site, reviewing various climate change models and evaluating possible flooding risk to the site.
When the structural and floor assessments had been complete, a redundant oil tank was identified on site. This required further investigation and assessment of any risk that the tank posed to the site at present and in the future, in terms of contamination. The position of the tank was in an active car park, between several columns and piles. The process of assessment needed to take this into account and still be located close to the tank to provide appropriate testing locations.
Flood assessment is rarely done and in Jersey and, due to the layout of St Helier, the engineers had to model the risk of flood based on potential various changes in sea level due to climate change. This task was definitely an interesting opportunity to evaluate possible changes to Jersey as a result of raised sea levels.
Southampton Hotel was constructed in 1820’s on reclaimed land adjacent to the St Helier harbour, in an area rich in historic significance, from the harbour and town development in 19th century to liberation at the end of the Second World War. By the early 2000s the condition of the building had deteriorated to the extent that it was no longer a commercially viable property and full redevelopment was decided upon. The redeveloped property now includes a restaurant on the ground floor and offices on upper floors.
The redevelopment included demolition of the dilapidated structure save the façade which was stabilised and incorporated into the new structure, and construction of new building including basement. The project constraints involved working on a confined site of an irregular footprint and tightly enclosed by a busy road to one side and a fully occupied hotel to the other, reclaimed site of varying ground conditions and high water level. The extremely complex project benefited from close cooperation between the client, architects, quantity surveyors, engineers and contractors and therefore various design solutions, the programme and cost implications, could be fully established.
Hartigan’s services included a Standing Building Survey, Level 3 in line with the guidelines by the English Heritage, design of repair strategy for the retained façade, design and supervision of groundworks, engineering design of the new structure, temporary façade restraint, innovative specialist piling to support the existing façade and full design of the Building Services.
The innovative micro-piling design used Cintec anchors to support the façade and Cintec masonry stitches provided means of integrating the façade and the new structure. The completed redevelopment provides modern office space and restaurant facilities, preserving the historic façade and maintaining the building’s character as a landmark property in the historic area of St Helier.
This project was undertaken as an extension of proposed improvements to drainage system at La Collette Boat Park. The initial proposal included for installation of new drains and extensive hardstanding for the placement of dry berthed boats.
Having investigated the existing material in order to determine its suitability for reuse or disposal, Hartigan determined that the material was significantly contaminated. A range of chemicals was identified, derived from the boat maintenance that has taken place on the site for a number of years. Although the client endeavoured to clean the site, the process of excavating of the material and disposing, followed by the installation of a hardstanding, was not feasible.
Hartigan liaised with a specialist supplier to create a system that would provide a contamination barrier to the underlying strata. A system was chosen which uses a biological layer to remedy contamination which, combined with containment barriers, provided a substrate for new hardstanding for the boats. The contaminated material was excavated then placed on top of the specialist membrane to prevent migration of contamination from the site. Further advice by Hartigan’s geotechnical engineers was provided during construction when, following heavy rain falls, problems with compacting excavated materials occurred. After completion in 2018, tests were undertaken on the boat park, which confirmed that there is no settlement beneath the boats and that drainage system is fully operational.
In an initial stage of the project, Hartigan was requested to undertake a detailed survey of reinforced concrete columns to a gantry at La Collette Power Station, and report on their condition. The age of the structure and exposure to elements resulted in significant defects to the concrete and the reinforcement. Following the inspection, Hartigan prepared comprehensive recommendations for repairs and, in some cases, replacement of the columns with steel elements.
Detailed specification and construction drawings were prepared for the works, which took into account numerous constraints and site challenges. Hartigan’s engineers assessed the project’s specific technical requirements as well as the Health & Safety requirements. The constraints included: the site must be operating throughout the works, the gantry is a support for high voltage cables, and there is limited access to one side due to adjacent rock. A detailed phased scheme was devised with comprehensive specification and technical drawings both for the repairs and replacement.
A number of areas on the Island are founded on weathered/broken rocky strata which may be subject to erosion, and rocky roadside banks have to be protected from landslides by appropriate systems. There had been several landslips in Mont Sohier area over the course of the last few years. In 2017 Hartigan were requested to undertake an initial visual assessment to allow conceptual design and costing to be prepared, in order to establish appropriate protection to the face of the bank and the road beneath.
The scope of the project involved determining how much to regrade the crest of the embankment and how to secure appropriate netting to protect the slope from further failure and from further erosion. After these initial stages we were also requested to finalise the design, comprising a combination of dowels and specialist netting. The system was successfully installed by the contractor in 2018.
The Summerland redevelopment, recently renamed Le Clos Curriard, is an extensive housing development for Andium Homes in St Helier, it includes three-bedroom townhouses and blocks of one and two-bedroom flats. Hartigan’s involvement comprises of managing the enabling works which entailed drainage diversions, asbestos removal, demolition of existing buildings and design of a new boundary wall scheme that secured the large party wall. Whilst this work was being carried out, Hartigan undertook the assessment of the the site investigation, design of the surface water attenuation system, design of the substation, drainage systems, as well as the structures themselves. This complex project involves our Structural & Civil team, Building Sciences team and Geotechnical team.
The site is formed on geology with a high water table and this needs to be taken into account in the design process. Information from the intrusive site investigation as well as drain surveys and a geophysics survey identified that a gravity drainage system was not feasible. Therefore, a large attenuation system was designed which collected the surface water from the site and stored in large aquacells before being pumped off site in a rising main to the nearby surface water sewer.
The principle of the design is a reinforced concrete structure of columns and flat slabs, with stair and lift cores providing stability, a podium slab transfers the load to the lower columns, which in turn transfers the load to ground beams and pile caps on to piled foundations. The townhouses, like the main apartment blocks, were designed utilising piled foundations with a reinforced concrete ground slab with a timber framed superstructure. The pile foundation system was selected not only to accommodate the loads of the new structures but also avoid the influence of the load from the new structures on to adjoining properties.
Other structures such as retaining walls and a substation were also designed as part of the project. The enabling works commenced in 2017 and the main phase of construction started in 2019 with an estimated completion in 2021.
Ports of Jersey established that maintenance works were required to the harbour basin in St Helier, comprising of and leveling of the sea bed in several sections of the site. Before this work could commence, a FEPA licence needed to be granted by the Environment Department and this required a process of testing of the sediment that was to be disposed.
In early 2016 Hartigan liaised with the Environment Department and agreed a scope of testing and the limits that could not be exceeded to allow disposal. Hartigan worked with the States of Jersey Department of Infrastructure dive team to obtain the samples required, as the typical sampling techniques, such as tube sampling or bucket sampling could not be utilised due to locations. Instead, dive sampling was used as it enables sampling at specific depths and locations.
Once these were tested the results were compared to the allowable criteria. A course of remediation was then agreed with the Environment Department, which included mixing zones of materials to reduce the overall impact of the disposed material. Hartigan then worked with the dredging contractor and the Ports of Jersey to mark out a series of known datum points for the dredging coordination and to work out the most efficient solution of dredging to allow the required mixing of sediment.