-contractor worried about existing wave-wall base
WITH Guyana geographically located below sea level, much emphasis has always been placed on the protection of its 430 km of coastland from the constant threat of sea level rise.
This protection is by way of a number of sea defence structures amounting to 340km in length, which, during the early years, were primarily designed to cater for overtopping.
But over the years, serious erosion at a number of areas of the earthen embankments which serve to allow the water to drain has caused existing wave wall designs to be substituted with the construction of a rock armour, commonly called rip-rap, sea defence structure.
The rip-rap structure is designed to last over a 30-year period and takes into account expected sea level rise, as well as adequate settlement of the structure which rests on a weak soil foundation.
Under the ongoing 9th EDF Sea Defence Programme, the reconstruction of 1.5km and rehabilitation of approximately 18km of sea defences is being undertaken by the local firm, B. K. International.
The $13,6M project is divided into Lots 1 & 2, and comprise a total of 34 sites with a deadline date of October 2011.
The contractor has reported an 31 per cent overall completion to date, media operatives were informed at a briefing Thursday chaired by Public Relations Consultant, Mr. Christopher `Kit’ Nascimento, at which Acting Project Manager, Dr Clifton Inniss and Mr Dayalgee Persaud, Admin Manager of B.K. International were also present.
Lot 1 consists of works at Springlands, Corentyne; and at Clonbrook, East Coast Demerara, for the demolition of the existing sea wall and the construction of 182.5m and 1,370m respectively of rip-rap and earthen embankment.
The work at Springlands is completed, and only 30 per cent remains to be done at Clonbrook.
Under Lot 2, the project sites are at Kitty, here in the city; at Montrose, Vryheid’s Lust, Better Hope, Melanie Damishana, La Bonne Intention, and Chateau Margot, all villages on the East Coast of Demerara; at Zeelandia, Wakenaam, and at Zeelugt, West Coast Demerara; Greenwich Park, on the East Bank Essequibo; and on the Essequibo Coast at Johanna Cecilia, Lima and Aurora.
At Kitty, work entailed placing 4,500m of three-inch-sized boulders between the Celina Restaurant, in the vicinity of the Kitty Pump Station and Pegasus Hotel, and this has been completed, while at Montrose, Vryheid’s Lust and Better Hope, work is 26% completed.
At Melanie Damishana, 27 per cent of the work — which comprises of constructing 300m of a new seawall of mass concrete, the repair of 600m of cracks and joints and the placement of 1,100 cubic metres of boulders along the toe, as well as construction of earthen embankment — has been completed.
At La Bonne Intention, 375m of new seawall of mass concrete is yet to be completed, while at Chateau Margot, 225m of new seawall of mass concrete is being constructed. At both sites, five per cent of the work has been finished.
Meanwhile, at Zeelandia, Wakenaam where 21 metres of rip-rap was to have been done, that work too has been completed, and at Zeelugt, there is 10 per cent completion of the construction of 553 m of new seawall, and 553m of new apron of reinforced concrete, along with the repair of cracks and joints measuring 1,175m, and the construction of an earthen embankment.
At Greenwich Park, the construction of 100m each of new seawall of mass concrete, new apron of reinforced concrete; the repair of 100m of cracks and joints, and the construction of 375m of rip-rap and earthen embankment is also underway, with three per cent of the works completed.
At Johanna Cecilia, where 50% completion has been achieved, work comprises the construction of 100m of reinforced concrete coping beam, the repair of 110m of cracks, and the construction of 320m of rip-rap and earthen embankment.
At Lima, where 400m of rip-rap and earthen embankment and a bridge are to be constructed, five per cent of that work is complete, while at Aurora, the contractor has finished the construction of 41 metres of rip-rap and earthen embankment.
In addition to updating reporters on the progress of the project, B.K. International on Thursday reiterated its concern about some aspects of it, whereby the sea defence is to be of a wave-wall design.
The company, which has its own quarrying operations and a cement plant, is not averse to constructing the wave wall, but as Nascimento pointed out, given its experience in these matters, their primary concern is about the stability of the existing base on which the new structure lies.
According to Nascimento, B.K. International has a preference for rip-rap, which has a 30-year lifespan, taking into account the projected sea level rise over the period at reference. Additionally, rip-rap has the propensity of catering for the adequate settlement of the structure, since Guyana has a weak soil type which makes the embankment subject to a lot of settlement.
The rock armour or rip-rap type of defence, Nascimento said, has the ability to cause wave energy to dissipate better and therefore precludes the need for a very high sea defence as would be required with a concrete structure.
Rip-rap, it is said, is cheaper to construct, and (except for the geo-filter fabric, which is imported)utilizes local materials. In addition, in some areas where rip-rap designs exist, mangroves — known as a first line of defence from the sea, and of which there is an avid regeneration campaign – have begun to re-grow.
Both Nascimento and Dr Inniss noted that the contractor has provided extensive evidence since March of this year to its client, the Ministry of Finance, to back up its concerns and show where wave walls have failed.
It was pointed out that the new structure of mass concrete will see a further five feet added to the existing height of the sea defence, which is about four feet at present.
With this new structure, height may very well pose a problem to some aged residents who may want to perform their traditional religious rites, and could also obscure the view of the sea of nearby residents.
The company has, however, received some reprieve with regard to its concerns, as a decision has been taken that instead of constructing the sea defences at Montrose/Vryheid’s Lust/ and Better Hope using the originally-planned wave wall design, it will now be constructed using the rip-rap design.
The client has also expressed a willingness to review the designs at nine other sites, reporters were told.
On Thursday too, media operatives were taken to Stewartville, on the West Coast Demerara, for a first- hand view of a rip-rap design completed by the contractor, which merges with an existing wave wall.
Persaud noted that “as a responsible contractor,” B.K. International has raised its concern with the client, but is obligated to proceed with the project as per its design and specification.
The work at Stewartville involved the construction of 551 metres of rip-rap wall at a cost of $221M with finances provide by the Government of Guyana under the emergency sea defence project.
The work on the seawall at Stewartville was as a result of flooding in early January this year from huge waves which overtopped the seawall and swamped yards and homes, resulting in furniture having to be removed and stacked on higher ground.
-contractor worried about existing wave-wall base