Redevelopment of Inverness Harbour is a vital first phase of Inverness Harbour Trust's plans for the waterfront. Over the course of a year 6.5ha of land has been reclaimed to extend the port and marina's existing facilities.
This work will pave the way for the Trust's eventual goal of creating the first Scottish five anchor-rated harbour under the gold anchor award scheme which rates the quality of a harbour's facilities.
This £8.5M investment in the waterfront has already attracted significant commercial interest, and the new 150 berth marina will be surrounded by a mixture of office and commercial premises, including restaurants and potentially a large chain hotel.
The first phase of the development started in July 2007 and is on course to finish in June, a month later than originally planned. Given the constraints of working within a busy port whilst limited to six hour bursts of activity because of the unpredictable tides, a one month delay is far less than might have been anticipated.
Ecological constraints were top of the agenda when work got underway. The harbour is at the mouth of the river Ness where it meets the Beauly Firth, and there is a large and well-known bottle-nosed dolphin community in these waters.
A rock armour revetment was installed around the marina once it had begun to take shape. This was put in early in the programme to reduce noise emissions caused by construction work. Experts from Aberdeen University were contracted to monitor the level of emissions.
Morrison Construction site manager Mark McLeman explains: "One of the first things we did was to put down rock armour around the whole marina to limit the noise during works. Because of the Bottle-nosed Dolphin community in the area, we were limited as to when we could put in the sheet piling."
He continues: "Everyone working on the project took the wildlife in the area into consideration at all times. Whenever we were tipping waste material on one of the local tip sites, if a dolphin showed up we had to wait for 20 minutes or so until it disappeared before proceeding."
Extensive reclamation work was needed to provide space for the new harbour and for future expansion of the port.
The existing foreshore had to be extended by in-filling the original 20 berth marina to which it was adjacent. Material suitable for infill was found under a 2.5m thick layer of silt in the river Ness while it was being dredged to provide clearer navigation channels for port traffic.
"The River Ness is dredged once every 10 years anyway, so it was just some minor widening work we did this time. It was a very useful source of good quality (infill) material for us," explains McLeman.
Two land-based excavators were used along with dredging vessels to remove 28,000m3 of silt, one of which is the largest long-reach excavator in the country, capable of removing 110 tonnes of material at a time.
Limited availability of landfill sites in the area meant that marine works subcontractor Land & Water Services, transported the silt to a nearby designated spoil site 35m up the river Ness.
The local dolphin population was not the only factor to impose time constraints on foundation work.
Construction of the marina wall required three concrete pours, two of which were using underwater concrete which had to be poured using a team of four divers (see diagram).
Around 1.2m of the 5.7m tall marina wall is below water level and so a four man dive team was required to place shuttering.
"Your four man team consists of the diver, a standby diver in case he needs an extra pair of hands and, for safety reasons, a tender and a supervisor," says Morrison Construction project manager Ian Johnson.
"It took us about three weeks to do 15 base pours with the underwater concrete, and we need to do 80 by the end. We've typically been getting about six hours to do these during neap tides (when the tide is at its lowest level), but the working team has to be very flexible as the tide dictates the schedule."
Construction of a 200m long sheet piled wall to form a new quay required more than 200 18m long piles. These were driven 7m below ground. Forming the quay required 120,000t of rock fill.
Inverness port currently handles vessels of sizes up to 4,000t, harbouring three at any one time. Most of the traffic at the port usually carries pallet-sized bulk materials such as timber from Eastern Europe, but Inverness is also a major distribution centre for imported oil to the north of Scotland, so there are some berths for tankers.
Once phase one is complete, additional facilities will be constructed to support the port's growth.