Montmartin-Hauteville-Annoville and Lingreville wastewater treatment authority is getting stuck into the renovation of the current Montmartin-sur-Mer WWTP, built back in 2005.
This WWTP’s incoming backflow station had one weakness: the input, via multiple force mains, of H2S gas (hydrogen sulphide) that oxidises the facility’s concrete structures and its upstream manhole.
The Rouen Regional Division was awarded this worksite as lowest responsible bidder in June 2020, proposing the construction of a new HDPE station, near the existing one, so as to guarantee a fully-waterproof and non-H2S sensitive facility.
The works, which began in August 2020, include:
- the fitting of an upstream manhole and the new 300m3/h, HDPE backflow station equipped with 3 pumps,
- the creation of a 200m3 storage basin,
- the creation of a 2nd back-up station featuring two 50m3/h pumps in case the storage basin overflows;
- the rehabilitation of the concrete pre-treatment tank, also damaged by H2S, including its by-pass.
N.B. This worksite is located 300m from the sea and near the Passevin canal.
So the water table, measured by the geotechnical survey 1.40m below the ground surface required the laying of sheet piles and the lowering of the water table using wellpoints for the earthworks (up to 6m deep).
The sizing of the sheet piles, the ballasting of the structures, the calculation memo and the stability of the structures were handled by SIng’s civil engineering teams. SADE synergy once more!
This worksite is a fine example of both SADE’s work on multidisciplinary projects and its wide-ranging expertise, including water-table lowering, sheet pile reinforcement, networks, hydraulic civil engineering and pumping techniques.
The Montmartin-sur-Mer WWTP is managed by the Montmartin / Hauteville / Annoville / Lingreville wastewater treatment authority. It collects effluent from 21,600 PE, routed by 5 pressurised pipes and 1 gravity sewer main.
