barre Port Grimaud
       10 years after the creation of the 1st tranche of PG1, the first problems appeared on the sheet piles...

barre Port Grimaud


       Why sheet piling instead of concrete quays?

       The PORT GRIMAUD company was new in its conception. The choice was made among several who favoured concrete… At the beginning of this enormous construction site, the promotion (thus Mr Spoerry) had enormous expenses to set up the general infrastructure: quays, dredging, streets, squares and buildings and houses. The right choices had to be made in terms of the solidity of the building materials and the prices, which had to be as low as possible. Iron was therefore preferred to concrete for the construction of the quays...
       When problems arose on the quays, the architect was criticised for having chosen this solution. But all the studies made for the repair or change of the sheet piles concluded that the architect had made the right choice…

barre Port Grimaud

The expertise :

       From the 1st to the 28th of April 1977, Jean Izard , an expert consultant engineer from Fréjus, carried out an expertise, requested by the Cabinet d’Architecture, with the mission of verifying the disorders noted and affecting the quays and the roadway of the 1st section of the lake city (i.e. 10 years after its construction). It was necessary to know if they were due to a "disturbance in the design of the works", to a "poor execution in relation to the rules of Art and the contracts" or to a "normal wear and tear due to the age of the works".

       These disorders appeared at the end of 1973, with scouring of the dyked sand with or without collapse of the pavement for the quays and a deterioration of the pavement for the streets…

       The first difficulties were identified on Quai de la Tartane (subsidence behind the coping) and Quai de la Giraglia (scouring - i.e. digging, erosion - of the stone coping).

       The expert report states that "the disorders observed consist essentially of scouring immediately behind the sheet piling curtain, between the surface of the earth and a coastline close to +0.25, i.e. the level of the sheet piling (upper level of the sheet piling)". These disorders are said to be due to "the suction of the sand by the tides, the stirring up of the water by the propellers of the boats in variable proportions according to the frequentation of the quays by the users and the exposure of these quays themselves. Pour que ce phénomène d’aspiration puisse se produire, il faut qu’il existe un passage à travers le rideau qui normalement sont étanches ».
       The expert leans towards the logical hypothesis of a vacuum between the sheet piles and the prefabricated part placed on top.

       In its general conclusions, it states that "generally speaking, it cannot be said that the disorders observed are the result of a design error:
- For the quay walls, these disorders would not have occurred if the contact between the sheet piling and the underside of the precast element had been good.
- For the tracks, the requirements adopted were normal.
       As far as implementation is concerned, we can say:
- For the quay walls, that more care should have been taken with the above-mentioned contact.
- the quayside disorders have been repaired and a systematic survey of the remaining untreated portions is to be planned in order to carry out the necessary repairs. "
       The discussions were long, animated and contradictory…

barre Port Grimaud

Cathodic protection :

       "The cathodic protection was not installed at the beginning because, at the beginning of Port Grimaud, there was very little electricity in the canals, the boats had their batteries disconnected out of season and the same for the fridges in the houses. Now PG is a real electric battery which produces "stray currents" which must be cancelled out by installing anodes on the sheet piles. You have to understand that these sheet piles are made of 4.7 mm thick steel..." (Jean Claude BONNET)

       On September 14, 1981, Mr. Giraud, CEO of BTM (which was involved in the construction of Port Grimaud), wrote to the company Spada, holder of the wharf contracts, that "the sheet piling wharves of Port Grimaud should be cathodically protected".

       A report by the company Der NosqueVERITAS (DNV) (world leader in cathodic protection and in conformity assessment and certification) of December 1, 1982, concluded that: "Cathodic protection proves to be the solution that must be envisaged to stop the corrosion phenomena encountered.
       The report added: "If an extension of the existing quays is to be considered in sheet piles, these will have to be cathodically protected from corosion by appropriate means".

       A study of October 1983 by the Central Technical Service of the Maritime Ports finally recognised that sheet piling was the best solution for the protection of the quays, compared to concrete, but with a cathodic protection of the whole.

       In 1985, the problem was still not solved...

barre Port Grimaud

François SPOERRY in the crisis :

       Some owners accused the promoters (i.e. Mr SPOERRY) of not having respected the correct thickness of the sheet piles, ironically referring to them as " pallets ".…
       In the minutes of the ASP1 Accounts Committee for the April 1985 General Meeting it was stated: "These large metal sections, on which all our wharves rest, have not stood the combined test of time and sea water. The examination, a complete inventory of the quays, carried out in December 1984, clearly shows the risks of collapse of whole sections in the years to come. Whether it is a question of preserving the value of our "home-grown heritage" or even of our responsibility towards third parties, we must act… together".

       François Spoerry addressed the PG1 Council on 17 October 1989 :
       « The deterioration of the sheet piles is a phenomenon that surprised all of us technicians, who had underestimated the oxygenation of the water by the very dense boat traffic, which is much higher than in any other existing port. The cathodic protection was only installed after 23 years, but the maintenance of this device during this period would have cost a considerable amount of money which should, logically, be taken out of the cost of the operation.. »

       He also took advantage of this intervention to recall some of the "gifts" made to the nascent Port Grimaud co-ownership in order to ensure its income! :

       « Finally, I would like justice to be done on the very important point of the resources of the car parks and moorings which I voluntarily left to the Syndicate Association, instead of acting like the other promoters, by reserving these important revenues for their company. I think that in view of the above, any person of good faith should admit that PORT GRIMAUD was, from the point of view of promotion, an exemplary operation, not only by the considerable capital gains that each unit generated, but also by the extent of the infrastructure made available to the community: common house, church, caretaker's lodgings, water tank, etc.… »

barre Port Grimaud

Repairs and checks :

       The Syndical Council of the ASP with its President Dr Bréhant had the choice :
- either clean everything, plug the holes and fit anodes
- or start a campaign of concreting the quays, knowing that the second solution will eventually be compulsory.

       After many meetings, the first solution was chosen. It was a huge job. When everything was in place, regular checks were planned.

       In fact, an attempt was made to concrete the quays on a small length, in front of the Harbour Master's Office, but this solution "brought forward" the limit of the quay on the canal to the detriment of the length of the moorings: In fact, concreting was tantamount to losing 1m of mooring! Hence the logical preference for installing anodes...

       Unfortunately the company in charge of these controls and which had installed the first anodes at the beginning of the 80's, went bankrupt and the Council asked, after deliberation and a call for tender which took place in Marseille, to entrust these controls to Jean Claude Bonnet whose son, Laurent had just restarted the maritime works branch.
       Very quickly it was realised that the previous checks were wrong and that after new, more serious checks, it was practically all the anodes that had to be renewed which was done in five years...

barre Port Grimaud

Jean Claude Bonnet says :

       "the first checks were more or less carried out seriously. So when a first set of anodes had to be renewed in 1998-2000, we were chosen to proceed with the installation of 600 anodes (following the controls of the company that had carried out the first job).
       When the first anodes were installed, we quickly realised that the control did not hold up and that next to the anodes that needed to be changed, which were certainly worn out, the neighbouring ones were in worse condition and no one was asked to replace them!
       Mr Martres was informed of the anomaly and asked us to carry out a more serious study. It was found that almost all the anodes were good to change quickly.
       The DNV drew up a new installation plan taking into account the anomalies found. In view of this scabrous episode, Martres asked me how I felt about the matter. I told him that in the long run the platforms would have to be concreted anyway.

       But a few years later, after a change in the Trade Union Council, Jean Claude Bonnet was "sacked" and the ASP called in a new company to monitor and replace the anodes...

barre Port Grimaud

Legal action :

       The ASP of PG1, in disagreement with the Promotion de la cité Lacustre (i.e. Mr SPOERRY), took the case to court insisting that the houses were in danger of collapsing, because of these disorders on the quays.

       The trial was long.

       In the meantime, Mr SPOERRY left us on 11 January 1999, his wife refused the inheritance but his son Bernard accepted it, with the outstanding debts and the lawsuit like a sword of Damocles over his head...

       The court ruled against the co-ownership because the experts, appointed by Bernard Spoerry, affirmed that the problem of the quays could not affect the solidity of the houses...

  THE WORK of François SPOERRY...

© Yves Lhermitte 2022   Reproduction prohibited without permission...