Hatch is conducting an independent engineer’s evaluation in support of project financing for the proposed 32-MW Pando and 52-MW Monte Lirio greenfield hydroelectric project on the Chiriqui Viejo River in Panama.
The project would produce an average of 429 GWh/yr. The Pando facility includes a 32-m-high concrete dam and impounds a reservoir with a daily regulating capacity of 500,000 m3. The Monte Lirio facility, located immediately downstream, will comprise a 15-m-high dam and operate as a run-of-river plant. The gross head of the development scheme is 380 m. The project also includes 13 kilometres of tunneling through lahar (i.e., landslide/mudflow-related deposits) using earth pressure balance tunnel boring machines. Additionally, low-cement mix, concrete dam structures will be founded on lahar.
Originally categorized as a Category B project (Equator Principles categorization), the Lenders made a decision to elevate the it to a Category A project given the lack of information regarding the environmental and social context and potential impacts of the project. EISA has commissioned a series of baseline studies to complement previous studies to satisfy the Lenders and the environmental authorities in Panama. The Lenders have committed to cooperate as much as possible with the developer to not delay financing and construction.
Hatch’s scope of work included a technical engineering review of the project as well as a review of the environmental and social aspects of the project according to the Equator Principles, IFC Performance Standards and the Corporación Andina de Fomento (CAF) Environmental and Social Safeguards. The project is being funded in part by the IFC, CAF and IADB (Inter-American Development Bank).
Principal challenges were the design and construction review of concrete gravity dams founded on low-strength lahar subject to settlement and long tunnels that use earth pressure balance (“EPB”) tunnel boring machines (TBMs). Hatch was able to provide the Lenders reasonable assurance of the level of contingency to assume for both construction cost and schedule. Hatch provided suggestions for commercial contract modifications, which was accepted by the project developer and EPC contractor.
The use of fibreglass lining rather than steel was an unusual design concept as proposed by the tunneling contractor, which reduced the contract price pipe over the steel alternative. Hatch’s review concurred with the EPC contractor’s proposal. Hatch’s review of the dam design addressed potential settlement concerns based on the proposed low-cement concrete mix and addition of construction joints that allowed for some settlement without structural cracking and associated excessive leakage that could impact project generation and revenue.
Other design and construction issues reviewed were river diversion during construction, seepage control of the dam foundations, sediment removal from the power flow for minimizing turbine wear, and independent power operation modeling to confirm the project sponsor’s energy estimate for peak and non-peaking periods.
Because of inadequate impact assessment and baseline studies conducted during the environmental impact assessment process, Hatch recommended that additional baseline studies be completed prior to construction, including socioeconomic studies and the identification of downstream river users; the identification of aquatic species and habitats, as well as terrestrial and avian communities along the affected river reaches, access roads and tunnel corridors; followed by an impact assessment and the development of mitigation plans to minimize any potential impacts.
Hatch also recommended that a cumulative impact assessment be conducted to include all aspects of the project (access roads, interconnection and tunnels not previously included in the separate Pando and Monte Lirio EIA reports) as part of the Transmission Line Environmental Assessment, which was still under way. The Lenders, under the direction of the IADB, are coordinating a cumulative impact assessment which included all other hydropower development (under construction and planned) along the Chiriqui Viejo River.
