Project scope
Plan: The existing run-of-river installation is described as having a roughly 415 m headrace canal, a Kaplan turbine in the existing powerhouse, a 16 m tailrace, and a weir; its reported baseline is 149 kW maximum gross power and about 780 MWh/year average generation over the preceding 18 years. The integrated proposal would widen and extend the headrace along its left bank, install a new turbine in a new powerhouse while retaining the existing building and recycling its equipment, replace the headgate, and rework the existing weir to add a fish pass and rebuild the boat passage. The new powerhouse is not to have a fish pass. About 11,300 m³ of excavated earth is to be made available to neighboring agricultural landowners. The proposed maximum turbine flow is 14 m³/s from November through May and 6.9 m³/s for the rest of the year; proposed maximum gross power is 597 kW. The opinion reports modeled annual generation of 2,423 MWh as the proponent’s more realistic estimate, while also noting a theoretical calculation of 2,610 MWh. The opinion says the currently authorized maximum diverted flow is 3.5 m³/s but that actual diversion is about 6.5 m³/s, reported in the file and confirmed during the exchange with the reviewers. It describes a current reserved flow of 10 m³/s.
Reported status and procurement
- Reported development
Plan: The works were described during the reviewers’ site visit as planned in two phases of six months each, scheduled for low-water periods. The opinion says the file does not clearly or consistently explain the works, their duration or sequencing. Described operations include dewatering the headrace for construction of the new powerhouse, followed by staged dewatering at the weir to widen the canal, install gates and repair the intake, then construct the fish pass and boat passage.
- Procurement availability
- Unknown / not established
Reported regulatory context
The environmental authority issued its opinion on 25 September 2025 after receiving the file on 15 July 2025. The opinion is neither favorable nor unfavorable and is not the authorization decision. The project is subject to environmental assessment following case-by-case review; the proponent submitted an environmental impact study voluntarily, and the described environmental authorization application also covers water-law and electricity-generation authorizations. The project is subject to Natura 2000 impact assessment. The opinion says the existing installation had not completed all compliance works prescribed in 2003 and lacked a water operating regulation. It also notes an earlier environmental opinion in 2016 and references to a public inquiry initially planned for 2017, whose status required clarification following regulatory changes. The supplied material does not establish whether the current application has since been authorized or whether a public inquiry has occurred.
A source report alone does not establish current progress or an open buying window.
Project summary
The Mouly hydroelectric plant, also called the Pont des Grottes plant, is an existing run-of-river facility on the Gave de Pau at Lestelle-Bétharram and Saint-Pé-de-Bigorre. SARL de Lauture is identified as its operator and project proponent. The proposal would expand the headrace, add a new powerhouse and turbine, and rework the weir to provide fish and boat passages. Proposed maximum gross power is 597 kW; the opinion reports 2,423 MWh/year as the proponent’s more realistic modeled generation estimate, distinct from a theoretical 2,610 MWh calculation.
The environmental authority’s opinion, dated 25 September 2025, raises concerns about ecological continuity, habitats, climate-related flows and sharing water with whitewater recreation. It calls for stronger analysis of hydrology and impacts. The opinion is neither favorable nor unfavorable and is not an authorization decision.
Evidence limits and unknowns
Whether the environmental authorization or other required permits were granted after the 25 September 2025 opinion, and whether public participation subsequently took place.
Construction start dates and the final confirmed works schedule. The opinion describes two planned six-month phases during low-water periods but says the file does not clearly explain the works, duration or sequencing.
Final detailed drawings and exact boundaries of excavation, infill, canal widening and work around the existing powerhouse; the opinion says these descriptions were incomplete.
The final operating and reserved-flow regime, including how it will address future hydrological conditions and balance ecological needs, electricity generation and water sports.
Project financing, named contractors, procurement arrangements and the identity of the electricity purchaser are not established in the supplied extracts.
The supplied text covers pages 2–12 and 27–28 of the 28-page opinion; pages 13–26 and graphical content were not interpreted.
