Northern Sewerage Project:Lining Selection in a Corrosive Environment

Old Brick Sewers

Long Time Coming

Location

Residential

Section along MPIS

Environmental Concerns

NSP1 Geology

Weathered Silurian along NDS Section 2 (NSP-1)

• Melbourne Formation (Silurian Age)

NSP2 Geology

• New Volcanics (Basalt)

Massive Basalt NIS Section 2 (NSP2)

Long Section NSP1 – NDS 2

Excavation Methods

(photo courtesy of John Holland/Melbourne Water)

• Tunneling (3 TBMs):• EPB 3-meter dia. = 4,700m• EPB 4-meter dia. = 3950m• Main Beam 3-meter dia. = 3190m

Primary and Secondary Support

2400 I.D Test Ring (photo courtesy of John Holland)

• 5 SEGMENTS PLUS A KEY• RIGHT, LEFT AND STRAIGHT

RINGS

Primary and Secondary Support

INITIAL SUPPORT (Rock Bolts)

Final Lining (RCP w/ Sac. Concrete, or FRPP)

1800

R 1500

Heavy Support Light Support

TIMBER BLOCKING

RING BEAM

BACKFILL GROUT

Spatial Constraints

NSP Stage 2 Support Types

Lining Required?

Lining Required?

Lining Required?

Lining Required?

Lining Required?

Lining Required?

Similar Projects

• Singapore DTSS• Pantai Trunk Sewer, Kuala Lumpur• Perth Main Sewer• S1 Sewer, Brisbane• Hallam Valley Main Sewer, Melbourne

Corrosion - Sulphide

Sulphate, SO4

Sulphide, S2-

Hydrogen Sulphide, H2S[aq][aq]

Hydrogen Sulphide, H2S[g][g]

Sulphuric Acid, H2SO4

Moisture on walls

Prevent sulphate reducing to sulphide - add oxygen, nitrate, reduce temperature, BOD, sulphate

Prevent sulphide converting to aqueous hydrogen sulphide - increase pH

Minimise turbulence to prevent hydrogen sulphide in liquid releasing to sewer atmosphere.

Ventilate to prevent hydrogen sulphide converting to sulphuric acid on walls

Liner impervious to sulphuric acid,

Control exits and treat odours.

Investigation

Sulphide and Ventilation

Models

Corrosion of unprotected concrete (>0.5mm/year?)

Durability Reports

Sewer Hydraulics

Minor Surcharge

Should NIS be lined?

Yes

No

Lining Options

S a c r i f i c i a l C o n c r e t eS e c t i o n

P o l y m e r C o n c r e t e

P l a s t i c L i n e dS e g m e n t s

A c i d R e s i s t a n tC o n c r e t e

O N E - P A S S( B G S )

C I P S a c r i f i c i a lC o n c r e t e

A G R U S u r e G r i pG S E S t u d l i n e r / A K S

C a r p i L i n i n g

L i n a b o n d

F l e x i b l eM e m b r a n e L i n e r s

C a s t - i n t o - B a c k f i l l

R C P G R P

E R O C R o s L o k

S e m i - r i g i dL i n e r s

C a s t - i n t o - B a c k f i l l

P l a s t i c L i n e dC o n c r e t e P i p e

K e r a l i n e L i n e dC o n c r e t e P i p e

G l a s s F i b r e R C P w / E p o x y L a m i n a t e

S t e e l P i p e w /E p o x y L i n i n g

F R P P

S t r u c t u r a l P i p e L i n e r

w / B a c k f i l l

T W O - P A S S( B G S + S e c o n d a r y L i n i n g )

F I N A L T U N N E L L I N I N G

Durability

Durability

Durability

Groundwater

Groundwater

Final Lining Selection

• MWC team• industrial catchment• deeper sewer• sedimentary• residential route• groundwater excluded• more $ in BG segments• more sewer drops

• higher risk of H2S corrosion

• required 100% liner• PE sheet

• YVW team• domestic catchment• shallower sewer• basalt• creek valley route• groundwater infiltration• less $ on segments• fewer sewer drops• accepted shaft risk,

avoided tunnel risk • preferred robust liner• GRP pipe

QUESTIONS?