Calcareous Deposits in Clear Creek Tunnel, California

Abstract

Research Article| January 01, 1977 Calcareous Deposits in Clear Creek Tunnel, California NIKOLA P. PROKOPOVICH NIKOLA P. PROKOPOVICH Nikola P. Prokopovich is with the U.S. Bureau of Reclamation, Regional Geology Branch, Mid-Pacific Region, Sacramento, California. Search for other works by this author on: GSW Google Scholar Author and Article Information NIKOLA P. PROKOPOVICH Nikola P. Prokopovich is with the U.S. Bureau of Reclamation, Regional Geology Branch, Mid-Pacific Region, Sacramento, California. Publisher: Association of Environmental & Engineering Geologists First Online: 02 Mar 2017 Online Issn: 1558-9161 Print Issn: 1078-7275 © 1977 Association of Engineering Geologists Environmental & Engineering Geoscience (1977) xiv (2): 105–128. https://doi.org/10.2113/gseegeosci.xiv.2.105 Article history First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation NIKOLA P. PROKOPOVICH; Calcareous Deposits in Clear Creek Tunnel, California. Environmental & Engineering Geoscience 1977;; xiv (2): 105–128. doi: https://doi.org/10.2113/gseegeosci.xiv.2.105 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyEnvironmental & Engineering Geoscience Search Advanced Search Abstract The study is a good example of the application of engineering geology to an operational-maintenance problem, a usage not often recognized. The Clear Creek Tunnel, a key feature of the U.S. Bureau of Reclamation (USBR) Trinity River Division of the Central Valley Project, is 17.7 km long, circular, 5.33 m in diameter, and concrete lined. It conveys stored Trinity River water into the Sacramento River Basin. Power availability at a hydro powerplant at the downstream end of the tunnel is subject to seasonal fluctuations of flow resistance losses, with maximum head (energy) losses during the summers. Annual electric power generation losses of some $80,000 have been estimated.The losses are related to numerous transverse calcareous “ridges” up to 4 cm high observed on the lining during several inspections of the tunnel. These ridges grow over minute irregular shrinkage cracks in the lining and are composed of calcium carbonate interlaced with fungal mycelium. During winter seasons the ridges are partially dissolved and have denuded crests. No carbonate deposits were noted at weep holes and at strong seeps.The ridges are developed by carbonates precipitated from CO2-rich ground waters which dissolve calcium carbonate from the concrete lining and grout before seeping into the tunnel. Inside the tunnel, the seeps release CO2 into the tunnel water and precipitate carbonate. Fungal growth in the cracks slows seepage rates and encourages deposition of carbonates. Winter increases of CO 2 content in reservoir waters related to the seasonal decrease of photosynthesis and decay of organic detritus, and some decrease in water temperature, reverse the process and lead to partial destruction of the ridges. Control by periodic scraping of the ridges is suggested. Construction joints in future tunnels may prevent cracking and the related development of ridges. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.