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GUIDELINES FOR THE CONSTRUCTION OF EARTH-FILL DAMS Water Resources Policy Policy #2008/1 November 2008 Department of Primary Industries and Water © State of Tasmania 2008 Water Resources Division Department of Primary Industries and Water GPO Box 44 Hobart TAS 7001 Phone: (03) 6233 6753, Fax (03) 6233 6055 Email: water@dpiw.tas.gov.au Home Page: http://www.dpiw.tas.gov.au/water ISBN 978-0-7246-6467-2 The Water Management Act 1999 (‘the Act’) provides for the sustainable management and allocation of Tasmania’s water resources. Amongst other things the Act provides for the promotion and fostering of social and economic benefits from the development of the State’s water resources. With the commencement of the Act in 2000, a new process for assessing dam permit applications was established. Under the Act, a dam permit is generally required for all dams except in circumstances such as: • a dam that is not on a watercourse and that holds less than one megalitre of water; or • a dam constructed for the primary purpose of storing waste as defined in the Act. In addition to a barrier across a watercourse, a "dam" includes an excavation in a watercourse and a flood levee, both of which also require a permit under the Act. Under the Act, a statutory committee, the Assessment Committee for Dam Construction (the Assessment Committee), was established as the body responsible for assessing applications for the construction of dams. The Assessment Committee members have expertise in the management of water resources; the use and economic development of water resources; engineering and safety matters relating to dams; integrated natural resource management; and best practice environmental management. The Guidelines for the Construction of Earth-Fill Dams detail the specifications for the construction of earth-fill dams, and outline the precautions and methods which should be employed in order to obtain the soundest possible structure. These guidelines will provide an overview for dam permit holders and existing dam owners of the major matters to be considered in the construction of such dams. Dr Alan Harradine General Manager (Water Resources) Department of Primary Industries and Water TABLE OF CONTENTS 1. INTRODUCTION ...................................................................... 1 1.1 Purpose of the Guidelines ................................................................... 1 1.2 Classification of earth-fill dams ........................................................... 1 2. PLANNING AND MANAGEMENT SPECIFICATIONS ............ 3 2.1 Introduction ......................................................................................... 3 2.2 Risk downstream of a dam ................................................................. 4 2.3 Contract .............................................................................................. 5 2.4 Easements & boundaries .................................................................... 5 2.5 Site investigations ............................................................................... 5 2.6 Filling of the dam ................................................................................ 6 2.7 Dam permit conditions ........................................................................ 6 3. ENGINEERING AND CONSTRUCTION SPECIFICATIONS .. 7 3.1 Engineering ......................................................................................... 7 3.2 Clearing .............................................................................................. 8 3.3 Foundation* ........................................................................................ 8 3.4 Cut-off trench* or keyway .................................................................... 8 3.5 When to use filters .............................................................................. 8 3.6 Rock .................................................................................................... 9 3.7 Outlet pipe .......................................................................................... 9 3.8 Outlet pipe materials and installation ................................................ 10 3.9 Baffle plates on outlet pipes .............................................................. 10 3.10 Borrow pits ..................................................................................... 11 3.11 Embankment compaction .............................................................. 11 3.12 Compaction testing requirements .................................................. 12 3.13 Batter slope* .................................................................................. 13 3.14 Settlement of the embankment ...................................................... 13 3.15 Vegetation ..................................................................................... 13 3.16 Spillway* or stream return.............................................................. 14 3.17 Freeboard*..................................................................................... 14 3.18 Protection from wave action .......................................................... 15 3.19 Sedimentation ................................................................................ 15 3.20 Maintenance and inspections ........................................................ 15 3.21 Your engineer ................................................................................ 16 4. ACRONYMS AND DEFINITIONS .......................................... 18 4.1 Acronyms .......................................................................................... 18 4.2 Definitions ......................................................................................... 18 5. BIBLIOGRAPHY .................................................................... 19 Version Author Reason November 2008 Water Resources Policy 2008/#1 released Division
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