February 21, 2003
Richard E. Goodman
13110 Pomo Lane
Mendocino, CA 95460
E-mail: REG@mcn.org
Phone/fax: 707-937-1018
To whom it may concern: Comments on the Feasibility Report for the Chalillo Dam Project, Belize

1. At the request of Mr. Tony Garel of The Belize Alliance of Conservation NGOs (BACONGO) and Mr. Ari Hershowitz of the Natural Resources Defense Council I reviewed documents concerning the planning and design for the Challilo Dam on the Macal River in Belize. I received sections of the final feasibility report by AMEC E&C Services Ltd dated Sept 2002, covering Geology and Geotechnics. I also received a copy of review comments by Mr. Brian Holland, Tech Director of Belize Minerals, Ltd.

2. I read the technical material provided by AMEC first and made notes. Upon reading the comments of Mr. Holland, I found that many of the points I had annotated as important were featured in Holland’s review as well. a) First and foremost of these is the assertion that the foundation rock includes much interbedded sedimentary rock and granite. This is highly improbable because granite is an intrusive rock formed at many kilometers depth within the crust, whereas sedimentary rocks represent the products of accumulation and cementation of sediments at the surface of the earth. Unless the entire foundation were composed of some sort of melange zone, or a complexly splayed thrust sheet, or the product of “lit par lit” intrusion, a mistake has been made in the identification of the rock types. The more reasonable explanation is that the report is in error. A close inspection of the rock with a hand lense or microscope would clearly distinguish feldspathic sandstone or arkose from granite because the former is clastic in texture whereas the latter is crystalline. Apparently Mr. Holland has examined the rock and judged that the supposed granite at the site is in reality an arkosic sandstone. b) Another point of inadequacy in the report was its professed ignorance with respect to the possibility of leakage through karstic limestone around the reservoir rim. The cavalier statements in the report with respect to this eventuality are not supported by documentation of any kind. Furthermore, the lack of confidence with respect to knowledge of the site stratigraphy engendered by reading this report allows the uneasy feeling that the possibility for soluble limestone occurring within the volume of rock forming the foundation or abutments can not yet be dismissed.

3. These criticisms of the site geologic description are not picky – they suggest a fundamental flaw in the most significant aspects of the site investigation. The geological makeup of a dam site affects the adequacy and acceptability of any specific design scheme. Without accurate geological information a site geotechnical model can not be developed and the resulting design will probably be seriously wrong in the large and the small.

4. The development of a satisfactory site geotechnical model involves not only a description of the type of rock forming all parts of the foundation, and abutments, but the structure of these rocks in great detail. At the design stage, it should be possible to predict all potential sliding surfaces within the foundation and all zones of potential leakage and/or internal erosion. These details are life and death information for construction of a gravity dam on sedimentary strata, especially where sandstones and shales are involved. Without such data, it is not possible to know ahead of actual construction what the final project will look like, or if it will succeed in fulfilling its intended purpose. It can be expected that there will be significant cost overruns, and the safety of the project can not be assured in advance. With respect to the safety of the project, the dam must not endanger the public or property or wildlife and ecology downstream. Since the feasibility report does not include graphs or data exhibiting specific structural information about the rocks, and since it gives little or no geologic interpretation sufficient to allow the creation of a geotechnical model for the site, the report must be judged as incomplete.

5. On the basis of the samples of the feasibility report that I have reviewed, I judge that the report is both inaccurate and incomplete. This means that the designers lack the information on which to provide an assuredly satisfactory and safe structure. Therefore it can not be stated that the project is feasible and it can not be established that the project is safe. No civil engineer or public authority can ethically venture a design and call for the construction of a work whose risk can not be assessed. This is especially true of hydraulic impoundments, which have the capacity to inflict great damage to life, property, and environment.

Sincerely,

Richard E. Goodman