In 2019, the town of Monistrol-sur-Loire, in the Haute-Loire department of France, entrusted Naldeo with several assignments, including the development of master plans for sanitation, stormwater management and drinking water. These studies were carried out concurrently, to gain a comprehensive understanding of the interactions between the various networks. Field surveys were carried out to gain a deeper understanding of how each system operates, and to identify the main malfunctions or inefficiencies. These data were supplemented by network modeling.
As far as wastewater systems were concerned, the main issues were the presence of untreated wastewater discharges into the natural environment and the abundance of parasitic clear water. Naldeo studied various technical solutions aimed at eliminating this pollution and limiting the infiltration of clear water into the networks and structures. Among other things, the program of works carried out enabled us to put an end to the discharge of around 200 population equivalents into the natural environment, to reduce the inflow of clear water by around 475 m³/day, and to neutralize around 43,000 m² of active surfaces.
About stormwater management, the main challenge was to avoid point-source overflows into the receiving environment during rainfall events of varying intensity. Naldeo explored various solutions, such as infiltration and retention of stormwater, with the aim of reducing peak flows at outlets. The action program implemented has resulted in better infiltration of small rainfall events at local level, and a reduction in peak flows during major rainfall events.
As far as the drinking water system was concerned, the main objective was to improve yields and guarantee a high-quality water supply for all subscribers in the years to come. Naldeo proposed solutions designed to optimize water distribution, while reducing volumetric losses, to meet the future needs of the population while preserving water resources.
This integrated approach has not only enabled us to identify problems specific to each network, but also to highlight synergies and cross-cutting solutions beneficial to the community. Thus, by adopting a global and coordinated vision, Monistrol-sur-Loire can implement more effective and sustainable actions to guarantee optimal management of its water resources and ensure a quality living environment for its residents.
The Naldeo group is a leading engineering and consulting firm specializing in the climatic and environmental transition of industries and local communities.