Development Application Part 2 of 2 Planning report Geotechnical report and plans MCU11/0168 & OPW11/0257

      PRACTICE NOTE GUIDELINES FOR LANDSLIDE RISK MANAGEMENT 2007



              APPENDIX G - SOME GUIDELINES FOR 111LLSiI)E CONSTRUCTION


                     Goon I;:VGLVIiIiRIVG PR.-1CTICF.
                                                                                                                                                              I
                                                                                                                                                              I
                                                                                                          POOR E.VGJ.\ L'L RLVG PRA CTICE
ADVICE
GEOTECHNICAL         Obtain advice (tutu a qualified. experienced geotcchnical practitioner at early                a:;o plan and start site works trf urc
ASSESSMENT           stage of planning and before site works.
PLANNING
SiIE PI:\.NNING      Having obtained gootcchnical advice, plan the development with the risk              Plan develpinent without regard for the Risk.
                     arising from the identified hazards and consequences in mind.
DESIGN AND CONSTRUCTION
                     Use flexible structures which incorporate properly designed brickwork, timber        Floor plans which require extensive cutting and
                     or steel frames, timber or panel cladding.                                           filling.
 HOUSE DESIGN
                     Consider use of split levels.                                                        Movement intolerant structures.
                     Use decks for recreational areas where appropriate.
SITE CLEARING        Retain natural vegetation wherever practicable.                                      Indiscriminate) clear the site.
    ACCESS &         Satisfy requirements below for cuts, fills, retaining walls and drainage.            Excavate and fill for site access before
   DRIVEWAYS

EARTHWORKS

       CUTS
                     Council specifications for grades may need to be modified.
                     Driveways and p arking areas may need to be fully supported on piers.
                     Retain natural contours wherever ossible.
                     Minimise depth.
                     Support with engineered retaining walls or batter to appropriate slope.
                                                                                                          geotechnical advice.

                                                                                                          Indiscriminate    bulk earthworks.
                                                                                                          Large scale cuts and benching.
                                                                                                          Unsupported cuts.
                                                                                                                                                              t
                     Provide drains c measures and erosion control.                                       Ignore drainage requirements
                     Minimise height.                                                                     Loose or poorly compacted fill, which if it lads.
                     Strip vegetation and topsoil and key into natural slopes prior to filling.           may flow a considerable distance including
                     Use clean fill materials and compact to engineering standards.                       onto property below.
       Fla-is        Batter to appropriate slope or support with engineered retaining wall.               Block natural drainage lines




  ROCK Ot TCttOPS
                     Provide surface drainage and appropriate subsurface drainage.



                     Remove or stabilise boulders which may have unacceptable risk.
                                                                                                          Fill over existing vegetation arc u,pnoi 1
                                                                                                          Include stumps, trees. vegetation, topsoil.
                                                                                                          boulders, building rubble etc in fill.
                                                                                                          Disturb or undercut detached blocks or
                                                                                                                                                              1
   & BOULDERS        Support rock faces where necessary.                                                  boulders.
                     Engineer design to resist applied soil and water forces.                             Construct a structurally inadequate wall such as
                     Found on rock where practicable.                                                     sandstone flagging, brick or umeinforced
   RETAINING
                     Provide subsurface drainage within wall backfill and surface drainage on slope       blockwork.
     WALLS
                     above.                                                                               lack of subsurface drains and wcepholes.
                     Construct wall as soon its possible after cut/fill operation.
                     Found within rock where practicable.                                                 Found on topsoil, loose fill. detached boulders
                     Use rows of piers or strip footings oriented up and down slope.                      or undercut cliffs.
    FOOTINGS
                     Design for lateral creep pressures if necessary.
                     Backfill footing excavations to exclude ingress of surface water.
                     Engineer designed.
                     Support on piers to rock where practicable.
SWIMMING POOLS       Provide with under drainage and gravity drain outlet where practicable.
                     Design for high soil pressures which may develop on uphill side whilst there
                     may be little or no lateral support on downhill side.
    DRAINAGE
                     Provide at tops of cut and full slopes.                                              Discharge at top of tills and cuts.
                     Discharge to street drainage or natural water courses.                               Allow water to pond on bench areas.
     SURFACE         Provide general falls to prevent blockage by siltation and incorporate silt traps.
                     Line to minimise infiltration and make flexible where possible.
                     Special structures to dissipate energy at changes of slope and/or direction.
                     Provide filter around subsurface drain.                                              Discharge roof runoff into absorption trenches.
                     Provide drain behind retaining walls.
    SL:RSURFACE
                     Use flexible pipelines with access for maintenance.
                     Prevent inflow of surface water.
                     Usually requires pump-out or mains sewer systems; absorption trenches may            Discharge sullage directly onto and into slopes.
     SEPTIC &
                     be possible in some areas if risk is acceptable.                                     Use absorption trenches without consideration
     SULLAGE
                     Storage tanks should be water-tight and adequately founded.                          of landslide risk.
    EROSION          Control erosion as this nay lead to instability.                                     Failure to obseive earthworks and drainage
   CONTROL &         Revegetate cleared area.                                                             reconimcndatiuns when landscaping.
  LANDSCAPING
DRAWINGS AND SITE VISITS DURINC CONSTRUCTION
    DRAWINGS          Building Application drawings should be viewed by geotechnical consultant
    SITE VISITS     i Site Visits by consultant may be appropriate during construction/
INSPECTION AND MAINTENANCE BY OWN I -
    OWNER'S           Clean drainage systems; repair broken joints in drains and leaks in supply
 RESPONSIBILITY       pipes.
                      Where structural distress is evident see advice.
                      If seepage observed, determine causes or seek advice on consequences.




                              Australian Geomechanics Vol 42 No 1 March 2007                                                                   113