Development Application - Part 2 of 2 - Report & Plans · OPW11/0116

The alignment of the revetment wall will follow the eroded top of bank. At the south-eastern end, the wall terminates at the
start of the mangroves. As natural levels of erosion are substantial in this area, it is expected that there could be some
flanking of the wall associated with erosion of the mangroves and, as such, a return detail will be necessary in this location,
although given the extent of the potential erosion, the return may need to be periodically extended.

Preliminary estimates have been prepared [Table 7 & Table 8].

Table 7: Preliminary cost estimate for revetment wall [rock option]
                                                                   Qty                      Rate                 Amount
                                                                                                                 ex-GST
Establishment                                                                                                    $50,000
Excavation                                                           1,500 m3                $12                $20,000
Supply & placement of geotextile [600R]                              1,500 m2                $10                $15,000
Supply of rock                                                       2,220 m3                $60                $135,000
Delivery and placement of rock bare                                  2,220 m3               $160                $355,000
Project management                                                                           5%                 $30,000
TOTAL                                                                                                           $605,000

Table 8: Preliminary cost estimate for revetment wall [mega-container option]
                                                                 Qty                        Rate                Amount
                                                                                                                [ex-GST]
Establishment                                                                                                   $100,000
Excavation                                                           6,600 m3                $12                $80,000
Supply & placement of geotextile [600R]                              1,500 m2                $10                $15,000
Supply mega-containers [vandal resistant eotextile                      25                $11,620               $290,000
Excavate, place and fill mega-containers                                25                 $6,000               $150,000
Project management                                                                           5%                  $30,000
TOTAL                                                                                                           $665,000

It was originally preferred to construct using rock due to concerns regarding the potential for damage. During stakeholder
consultation, it became evident that there were concerns regarding the use of rock, the difficulty of removal and the visual
impact. At this stage, the preferred option is the sand-filled mega-container wall, although if maintenance becomes an
ongoing issue, consideration may be given to rock armouring.

     6.4.   Groynes

While the upstream areas of Noosa River Spit are not as popular as the central sections, the creation of a beach along this
section of foreshore will likely encourage increased usage and, as such, any structures placed in this location should be
user-friendly to ensure access along the length of the foreshore. Placement of rock structures across the foreshore will likely
restrict access and introduce safety hazards associated with voids in the structure and, as such, are not desirable. While
construction could be undertaken using geotextile mega-containers, as is proposed for the submerged "closure", the
changing seabed levels over the length of the structure mean that this will result in a need for significant excavation and will
not provide an efficient design. Construction of the groynes using smaller 2.5m3 sand-filled geotextile containers [Figure 471
is preferred. This has been undertaken very successfully and is also deemed to be suitable for this location.




Figure 47: Groyne constructed using 2.5m3 sand-filled geotextile containers

Preliminary design has been prepared [Figure 48].