Flooding in France (Ile-de-France and Yonne)

Events

 
In late May 2016, France was widely affected by heavy precipitation. Several days of exceptional rainfall in the areas of Île-de-France, Picardy, Bourgogne and Centre led to swollen rivers and severe flooding. These events caused oil and chemical pollution across extensive geographical areas, in several regions of the country. Three departments which were particularly badly hit called upon Cedre: Seine-et-Marne, Yonne and Essonne.
A wide variety and large number of facilities were affected: oil storage facilities (both new and waste oil), fuel tanks, etc. The pollutants spread across vast areas of flooded land and travelled along many rivers in spate. Natural areas, infrastructures and residential buildings (individual houses and blocks of flats) were contaminated, including underground parts (garages, cellars...). The local authorities and fire brigades – already heavily mobilised to mitigate the damage and risks generated by these exceptional events – also had to handle this "diffuse" pollution issue. 
Cedre was called out and sent agents on site as of 5th and 6th June. Requests came from various parties: the Seine-et-Marne fire brigade, the Evry Prefecture in Essonne and the city council of Charny Orée de Puisaye in Yonne. These missions lasted from a few days to a few weeks. In addition to attending meetings, the agents from Cedre handled many requests for support in the field.

Surveys and situation assessment

 
The first requests were for assistance in assessing the situation. In Yonne, one main source of pollution was identified and flooded cellars with overflowing heating fuel tanks were also reported. Elsewhere many scattered sources were identified and were often difficult to locate. Certain sites or homes were closed off or shut down, others were difficult to access due to the flooding.
The pollution had spread very widely, carried by the flood waters as the water levels rose then fell. Helicopter overflights were conducted to monitor its spread along the watercourses, observe the containment systems deployed (mainly floating booms) and recommend alterations to optimise the set-up. Very soon, these investigations were further supported by surveys conducted on land, or even by boat when the streets were flooded. New recommendations on containment techniques and equipment were issued to support emergency response operations. In particular, they included advice on setting up custom-made barriers and filter systems, as conventional booms were unsuitable for certain sites.
Many individual homes were affected by the oil, meaning that "door-to-door" visits had to be organised to obtain an accurate estimation of the extent of the pollution and to define ad hoc technical recommendations. These surveys were conducted jointly with the city councils and local authority staff, fire brigade personnel and other services.
  

Response in flooded cellars and underground carparks

Another urgently needed action was to pump up the large volumes of contaminated water out of flooded sites (cellars, underground carparks). Cedre assisted the Seine-et-Marne fire brigade in designing and building makeshift filtration systems made of bins with a perforated base filled with loose sorbent. These systems were used to evacuate the water from these sites and release it into the natural environment. Technical datasheets were also produced by Cedre and distributed.
Health concerns rapidly emerged. A memo jointly produced by the Ile-de-France regional health agency (ARS), the Seine-et-Marne authorities, the Seine-et-Marne fire brigade and Cedre was released on 8th June for the general public and provided instructions on what to do in case of response actions in flooded and contaminated properties and cellars.

Defining a sampling plan

  
Cedre helped to define a sampling plan, managed by the Seine-et-Marne unit of the Regional and Interdepartmental Directorate for the Environment and Energy (DRIEE), so as to characterise the main types of pollution observed.
 
 

Recovery on the water

  
When the site configuration caused sufficiently thick layers of floating oil to accumulate, this oil was recovered by pumping, sometimes used in combination with skimmer heads. However, in more open areas, the extensive spread of the product at the water surface meant that sorbents were the only viable option.
 

 
 
Sorbent booms were also laid as "sentry" devices, or near to points of pollution resurgence, or else in a protective capacity for certain sites.
Very quickly, the quantity of sorbents required, and their installation, surveillance, renewal and treatment once oiled became an issue in itself. This came in addition to the problem of storing and processing the large quantities of litter and debris, whether oiled or not, generated by the flooding. Improvised storage areas were set up locally, sometimes in very restrictive conditions given the complex circumstances. In certain cases no ground protection was laid, creating a risk of secondary contamination.

Clean-up of houses and gardens

 
In terms of the pollution deposited when the water level dropped, Cedre was questioned on the clean-up techniques to be implemented in homes and gardens, the equipment to be used and the available contractors. These recommendations were used to conduct clean-up, but also as supporting documents for insurance claims.
The techniques recommended for gardens are similar to those used during the "botanical clean-up operations" implemented in oiled natural vegetated areas: scything, selective cutting, scraping, or even removal of a few centimetres of soil. In terms of the clean-up of hard surfaces, the emphasis was on the urgent need to contain, recover and treat washing effluents.
Some of the questions asked did not fall within Cedre's field of expertise, in which case the enquirers were referred to the French geological survey BRGM for probing and sampling polluted soil and the regional health agency ARS for questions relating to health. 
Within the limits of its field of expertise in relation to these concerns, Cedre drafted an observation record and recommendations for each site visit. Cedre also produced a general framework memo, intended for mayors in Essonne. This document was rapidly generalised to apply to the other areas affected.
Cedre completed its field mission at the end of June, but continued to provide remote assistance from Brest to the BRGM and the authorities until the end of July, in particular by fine-tuning the initial recommendations made and mapping the visits made.
  
  

Summary and feedback

  
The severe flooding of June 2016 led to rather unusual pollution in several respects: vast geographical areas affected, very high number of sites contaminated (around 90), numerous sources of pollution, different types of pollutants (oil, plant protection products, etc.) all in the context of a natural disaster.
Particular attention had to be paid to responder safety as personnel were required to work in places that were particularly difficult to access such as flooded cellars of houses or areas of marshland. The risks were aggravated by the possible presence of volatile toxic compounds (VOCs, H2S) and submerged hidden hazards (storm drains, branches, various objects, etc.). Another very important aspect which was a major focus for all those involved in the response was the issues relating to the safety of inhabitants as well as the health and hygiene of the homes and gardens affected.
In terms of spill response, original solutions were implemented using the resources available on site. Waste management, for pollutants, contaminated objects and used sorbents, proved complicated due to the extremely high volume of waste involved. 
Among the lessons Cedre drew from this response, we note the benefit of the surveys conducted jointly with the fire brigade or representatives of the local authorities. This made it easier for Cedre responders to access the various oiled sites, a crucial factor in obtaining a full understanding of the issues at stake and in providing appropriate technical guidance.