Appendix D - Engineering Report · REC15/0011

Page 2

Proposed Subdivision
1 George Tewantin




    Unitywater indicated their preference was for the whole of the site to be commanded
    by a gravity sewer with the sewer mains being located on their standard alignment
    within the road reserve, but acknowledged that if Council wished to retain trees
    within the road reserve then they would consider alternative alignments.

    We have investigated the use of bio swales and grass lined swales in lieu of bio
    retention basins and found that bio swales are less effective than bio retention
    basins due to the lack of detention time of water over the filter media. This results
    in a greater area of swale being required compared to a bio retention basin and
    thus the long term maintenance requirements for Council would effectively be
    greater not less.

    Our concept design therefore proposes bio retention basins to treat the stormwater
    run-off from the site, however instead of on larger basin, two smaller basins have
    been proposed to minimise impacts on existing trees and to make use of the natural
    lay of the land. Following discussions with Council at the prelodgement meeting,
    water from the lots is conveyed to the bio retention basins via a conventional piped
    interlot drainage system. A gravel access is proposed down the eastern and
    western side of the site to provide access for maintenance of the bio retention
    basins.

    In regard to run off from the existing road and footpath area of George Street,
    Council has indicated a desire retain the flush kerb detail instead of replacing this
    with a conventional kerb and channel. As such it is proposed to provide a grass
    lined swale drain on the low side of the existing footpath. This will convey run off
    from the road from the crest about mid-way along the frontage to each end of the
    site.

    At the western end this drain will be directed into the Council reserve and ultimately
    to Wooroi Creek. At the eastern end the drain will be directed into a field inlet and
    the stormwater piped to the rear of the battle axe blocks where it will be discharged
    and dispersed as overland flow to the existing gully that drains to Wooroi Creek, as
    is currently the case. It is proposed that future driveways servicing the new lots be
    constructed with pipe culvert crossing of the swale drain in lieu of a standard urban
    driveway profile. This has been depicted on the concept plans.




    J/N 15513                                                                    May 2015
     Rev B                                                                      Page 2 of 3

Page 3

Proposed Subdivision
1 George Tewantin




        4. CONCEPT DESIGN FOR WATER AND SEWER

    In regard to the sewer service we are able to command all of the new lots using a
    gravity sewer system connecting to an existing sewer manhole in George St. To
    avoid trenching adjacent significant trees along the frontage on George St we have
    elected to take the sewer down the side boundary of lot 1 (in the balance lot) on an
    alignment that avoids any existing significant trees. At the back of lot 1 the sewer
    then traverses the rear of the lots fronting George Street to service these lots
    avoiding significant trees. The battle-axe lots are serviced by two sections of sewer,
    one along the side boundary of lot 2 and the other between lots 8 & 9, again
    avoiding existing significant trees. The proposed sewer system has been forwarded
    to Unitywater for initial comment.

    In order to avoid disturbance of significant trees at the George Street frontage the
    water service to each block has been positioned accordingly. Two road crossings
    are proposed to avoid the trenching in front of a large tree in the front of proposed
    lot 1 and lot 10. Note a similar approach is proposed for the underground electrical
    service.

    The above information is provided in support of the response to Council’s
    information request dated 26 November 2014.



    Prepared by
    Doug Reynolds
    RPEQ 9072
    Tod Consulting Pty Ltd
    11 May 2015




    J/N 15513                                                                    May 2015
     Rev B                                                                      Page 3 of 3

Page 4

 

 

 

 

Edge of

aan , EXISTING CREST

Bitumen?

 

 

 

 

    

 

         

 

 

 

 

 

 

     

 

 

 

 

 

 

 

 

 

  

 

        

 

 

 

 

 

 

 

 

 

 
  

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

DISCHARGE —/ (APPROX. +
INTO CREEK L . LOCATION) |
7 _
Ye = > = >. .
Le PROPOSED
. : PROPOSED GRASS 3
GRASS SWALE DRAIN~|
SWALE DRAIN
3.0m WIDE 2
GRAVEL
NS ACCESS 1 0 T 5 4 + 1 =
2 -
+ 5 L
oO
* ‘ + 2 Cc
1 |
|
wo———rwo
 — awo———Rwo a RWD 3
3.0m WIDE i
GRAVEL ACCESS ‘ J 46
a T16321
8 6 3 2 -
ae
a 300 RCP
ye
+ ey —awo awo-s-26nRwo—[E-Rwo wo wo
' 2 PROPOSED
5 . 9 | BIORETENTION
B 03m BASIN = 95m?
s 8m : 3 (TO BE
PROPOSED 16m CONFIRMED)
\% s BIORETENTION . , |
\ BASIN = 73m? + 415 at
\ O (TO BE CONFIRMED) rs
oO —
3 © —
oe
- =
Gum
\ ° @ 0.5r a
— s 12m a
oO \ H 25m Y o
\ ww
WD \ sO
Oy
l rl \ AR 0 5 10 15m
m + a
\ 7 Scale 1:250 @A1
~ \ 4 Scale 1:500 @A3
/ 4
Associated Consultants Client Drawn Verified Project Drawing Title Scale |Sheet Size]
SUNSHINE BEACH T D lia But DR RESIDENTIAL SUBDIVISION PRELIMINARY AS SHOWN] A1
CONSTRUCTIONS BLH DR 1 GEORGE ST, TEWANTIN STORMWATER DRAINAGE Drawing Number
S074 SWALE DRAINS DELETED aH PTY LTD engineers & projectmanagers [PP ng Gor0 ROP monty LAYOUT PLAN 1 of 2
110.04.15| SWALE DRAINS ADDED BLH Signed Date New erent HORIZ DATUM om) 6 SOO Sheet Revision|
78.08. F
rsa Date [Revision Description ~ Drawn Sn Ree Be ATM AND dal 15513-SK01| C

 

 

 

Page 5

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Je ap ig ooo —— “ ° +
a _ GEORGE STREET \ 1 5
ae Ee + 4% a
S SS 5 ee fo + — a aT
Wry i — toss ‘| am
. | Zz
. ? <
! ao. =
no kL
7 5 4 f zZ °
+ Oo Cc
7
| 2.500 \
s——_¢—-s s s s J J s s—6—fs s s s——fs - s s s + \Y
| : S
° 1116321
L. sss sf ws
_] rw
: s s s s—®
’ rN
Gum ° C )
@ 0.3m
s 8m
H 16m *
EmtA 115.68 / 114.63 ot s
SEWER MH LEVEL TO BE CONFIRMED é
Ww d
> /
O J
co }- /
< . /
Zz * ,
= |. . J
— + /
o s s s s s s s s s s s s s——6
0 5 10 15m no
a
Scale 1:250 @A1 =
Scale 1:500 @A3 oO
4
‘Associated Consultants Client Drawn Verified Project Drawing Tile Scale [Sheet Size|
SUNSHINE BEACH Bu oR RESIDENTIAL SUBDIVISION PRELIMINARY SEWER AS SHOWN] At
CONSTRUCTIONS BLH DR 1 GEORGE ST, TEWANTIN RETICULATION LAYOUT Drawing Number
(06.05.14 SWALE DRAINS DELETED BLH PTY LTD D REYNOLDS 9072 “° POcaL AUTHORITY 2 of 2
fos 3 SWALE DRAINS ADDED — au Signed Date CU APPROVAL HOR DATUM oO Sheet Revision|
[8.03.1
Date [Revision Description Drawn OPW APPROVAL RL ° MEASUREMENT BAR - INCREMENTS IN mm 15513-SK02 | C