kak
a
Te Wh
no
akaki
a Wh
oreng
PREVENTING
WASTEWATER OVERFLOWS
Aukatia te waipara e maringi noa ana
PREVENTING WASTEWATER OVERFLOWS
I
How you can help to prevent costly sewer blockages
and wastewater overflows.
Pehea e taea ai e koe te awhina
REPORT POLLUTION
TO TAURANGA CITY
COUNCIL
PH (07) 577 7000
Information in this book is correct at the time of publication
April 2011
INTRODUCTION
CONTENTS
Introduction
1
How your sewer system works
2
It’s a big cost to us all!
3
What does a wastewater overflow
look like?
4
What can cause a wastewater
overflow?
5
What is a gully trap?
9
Wastewater overflows – protecting
your health
10
How you can prevent blockages
and overflows
11
How Council responds to
blockages and overflows
12
Tauranga City has around 1200 kms of
wastewater pipe network, 10,000 manholes
and 140 pump stations. These sewer pipes
carry the waste from houses and businesses
to be treated at the City’s Wastewater
Treatment Plants.
Once this waste has been treated, the treated water
component is discharged into the sea and the treated
biosolids are taken to a consented landfill for disposal.
If blockages or breaks occur in the network the result can
be raw sewage flowing into our harbour. Overflows are
a health risk and beaches may be closed to the public.
Overflows are expensive to clean up and cost ratepayers
thousands of dollars every year.
What you wash down the sink or flush down the toilet is
pumped to the treatment plants. Every year in Tauranga
foreign objects, fats and oils, rags, towels and nappies
cause blockages that result in overflows.
This booklet gives you important information on ways you
can reduce the risk of causing sewer overflows.
THE TWO
EVERY YEAR
T
R TREATMEN
WASTEWATE
D
CESS AROUN
PLANTS PRO
UBIC METRES
10 MILLION C
OF WASTE.
Chapel Street Wastewater Treatment Plant
PREVENTING WASTEWATER OVERFLOWS
1
1.
HOW THE SEWER SYSTEM WORKS
Anei ta te punaha tuku para mahi
Your house or business' wastewater pipes are called
service lines (or private lines). These service
lines run from various sinks, showers and toilets in
your home or business to connect with the
public wastewater network.
Every time you flush your toilet the wastewater can travel
many kilometres, through one or more pump stations
before arriving at one of the treatment plants. Treatment
plants then have to screen and process all of
this waste before it can be disposed of.
The public wastewater network includes pipes and
pump stations which take wastewater from houses and
businesses to one of two wastewater treatment plants in
the city at either Chapel Street or Te Maunga.
Our treatment plants work primarily through biological
processes, with good bacteria eating bad bacteria.
Unfortunately many items like gloves, wipes and
disposable nappies are also flushed away. Items like this
are not biodegradable so they have to be screened and
removed before treatment continues. This adds cost and
complexity to the treatment process. These items should
be disposed of in your domestic rubbish. Once waste
has been treated to remove harmful chemicals, bacteria,
viruses and other nasties the treated wastewater is
discharged into the sea.
The service lines are the property of the homeowner
and the maintenance and operation of them is the
responsibility of the home owner. Operation and
maintenance of the public network is the responsibility
of Tauranga City Council.
Gully trap
Wastewater manhole
Council main wastewater line
2
BEST PRACTICE GUIDELINES FOR STORMWATER POLLUTION PREVENTION
2.
IT’S A BIG COST TO US ALL!
He nui te utu ki a tatou katoa
It costs the Council a great deal of money to clear
blockages and clean up overflows created by residents
who treat the sewer system as a rubbish dump. These
costs are funded as the wastewater component of the
rates. Regular clearing of pipes cost thousands of dollars
every year.
Cleaning up after a sewer overflow
A single overflow alone can cost over $5,000 for
investigation, clean-up and water quality monitoring.
If beaches have to be closed this will be inconvenient for
beach users, events may also have to be cancelled and
this all costs Tauranga City, and therefore you, money.
There are also significant environmental costs for aquatic
life and health risks for the public.
Flushing items such as latex gloves, rags, cotton buds,
nappies, medical wipes and other foreign objects down
the toilet can result in the blocking of pumps at pump
stations. The cost for unblocking or repairing a single
pump can be over $3,000.
Clearing a blockage can cost thousands of dollars
Remember that everything you put down the drain has
to be treated and it’s a very expensive business. The
less water you use, the less wastewater you create. This
means you'll pay less for wastewater treatment (in your
rates) and less on your water bill.
If a blockage occurs on your property then you or your
landlord will have to pay the cost for a plumber to fix the
problem and this could be hundreds of dollars.
WATER
E
T
S
A
T
W
S COS
W
O
L
F
OVER
PAYER
E
T
A
R
HE
RS
YOU, T S OF DOLLA
AND
THOUS
PREVENTING WASTEWATER OVERFLOWS
3
3.
WHAT DOES A WASTEWATER OVERFLOW LOOK LIKE?
Pehea te ahua o te waipara, maringi noa?
Sewage spills can range from just a trickle of wastewater
to a very noticeable gushing from a manhole or gully trap.
As a general rule in Tauranga wastewater manhole covers
are painted white (stormwater manhole lids are generally
painted blue). If the leak is underground wastewater may
be visible bubbling up through the ground. For serious
overflows “solids” and toilet paper may be visible. Minor
overflows may look more like a water leak. Usually with
overflows there is an unpleasant odour.
Look for:

Broken sewer pipe discharging wastewater to an open drain
Back-ups in drains inside your home.
 Water
leaking around manhole lids onto your property or the street.
 Leaking
 Water
water from outside drains and gully traps.
bubbling up from underground.
 Unusual
foul smelling wet areas which may
have deposits of faecal matter, toilet paper
or sanitary products.
Manhole overflowing due to a blockage
IF YOU
NOTICE
THESE
SIGNS ANY OF
CALL T
COUNC
HE
IL IMM
E
D
IA
PH (07
) 577 7 TELY
000
4
BEST PRACTICE GUIDELINES FOR STORMWATER POLLUTION PREVENTION
4.
WHAT CAN CAUSE A WASTEWATER OVERFLOW?
He aha tera i taea ai te maringi noa o te waipara
4.1 Foreign Objects
Although some wastewater overflows are caused by
defects in the network, the majority of overflows are
caused by residents flushing things they shouldn’t down
the sink or toilet.
Your toilet and sink are not rubbish disposal units. If it is
not wastewater from your toilet, sink, shower or washing
machine, then it should NOT be going down the pipes.
Your wastewater (or sewer) pipes are designed only for
wastewater to be collected. Avoiding blockages also
means avoiding plumbing bills.
Causes of wastewater overflows in Tauranga
6%
Tree roots
10%
Third party damage
24%
Cause unknown
20%
Foreign objects
12%
Network faults
28%
Fat
PREVENTING WASTEWATER OVERFLOWS
5
Do not flush any of the following:
Kaua e tukua kia rere te wai mo enei e whai ake nei

Strong chemicals

Wood

Rocks and concrete

Plastic wrapping

Cigarette butts

Kids toys

Cotton buds

Dental floss

Disposable nappies

Medical wipes

Condoms

Feminine hygiene products

Towels

Rags

Baby wipes

Clothing

Underwear

Surgical gloves

Fats or oils

Waste engine oil

Anything else that is not organic/biodegradable
L
S, DENTA
D
U
B
N
COTTO
IES AND
P
P
A
N
,
FLOSS
ES CAN
P
I
W
Y
B
BA
SEWER
E
S
U
A
C
ALL
GES
BLOCKA
6
BEST PRACTICE GUIDELINES FOR STORMWATER POLLUTION PREVENTION
An entire deep fryer retrieved from a sewer line
Kids toys caused a blockage and an overflow to the harbour
Rags flushed down the toilet blocked a wastewater pump station
4.2
Fats, oils and grease
Nga momona, nga hinu me nga pera
Hot fat, oil and grease tipped down the sink do not travel
far before they cool down and solidify resulting in pipe
blockages. Tipping hot water down the sink just moves
the problem further down the system.
Collect cooled fats, oil and grease in a covered container,
plastic bag or newspaper and dispose of it in the rubbish
bin or put it in the compost bin or worm farm.
Restaurants and other food premises are a significant
source of grease and fat that are used in cooking. These
businesses must have a grease trap plumbed into their
waste system to collect fats and oils.
Tipping fat down the sink and washing it through with hot water only moves the
problem down the system
4.3
Tree Roots
Nga take rakau
Tree roots find their way into the wastewater network
through joints in the pipes (older pipes in particular). The
roots cause blockages as they grow and restrict the flow
in the pipe.
This can result in the tree needing to be removed. If the
tree is on private land and is causing problems in the
wastewater network, then the cost of tree removal may
be charged to the landowner. Before planting a tree,
owners should consider the likelihood of that tree
causing damage to underground pipes. Choose plant
locations carefully.
Tree roots growing into manholes or pipes can cause blockages
PREVENTING WASTEWATER OVERFLOWS
7
4.4
Third party damage
Ngaa roopu tuatoru whakakino
Contractors can damage or break sewer lines. Heavy
machinery or directional drilling can damage pipes and
contractors may not be aware of the problem. Everyone
working around sewer pipes must know where they are
located to ensure they are not damaged.
4.5
Vandalism
Mahi taurekareka
Exposed wastewater pipes can be damaged or broken by
vandals, and there have been cases of manhole covers
being removed and foreign objects deliberately dumped
into the wastewater network.
Hundreds of rocks deliberately dumped in a sewer manhole.
This caused a major overflow
8
BEST PRACTICE GUIDELINES FOR STORMWATER POLLUTION PREVENTION
4.6
Inflow and infiltration
Te paringa me te urunga mai
During heavy rain, sewer drains can become overloaded
when stormwater enters them, causing overflows. Often
the overflows are caused by stormwater entering cracks
and breaks in private sewer drains that connect to Council
pipes. Inflow from house gully traps during heavy rain is
a big contributor.
Infiltration is the entry of groundwater and stormwater
into sewer pipes below ground, which can substantially
increase the wastewater flow in the pipe. It can also
contribute significantly to wet weather flows.
Council is actively trying to reduce this by undertaking
inspections of residential gully traps, and working with
residents to remedy any problems found.
Overflowing sewer manhole during heavy rain
5.
WHAT IS A GULLY TRAP?
He aha te awaawa rerenga wai
Gully traps are small drains, usually located beside your
house’s foundations, outside your kitchen, bathroom or
laundry. It may have a grate or cover over it to keep out
leaves and other debris. A gully trap can have up to four
waste pipes draining into it and should be raised above
the ground to prevent stormwater from the roof or ground
draining into it.
House gully trap
If rainwater can enter your gully traps they need to
be fixed. It is the landowners responsibility to do this.
Rainwater entering gully traps is a major cause of
wastewater overflows during heavy rain. Contact Council
for advice on how to inspect and fix your gully traps.
Don’t confuse your gully trap with a stormwater drain –
houses often have small drains around the outside and
these lead directly to rivers and the sea.
Remember all the water that washes off your roof,
driveway or the street flows directly into streams or the
harbour.
Illegal gully trap allowing rainwater to enter
Small stormwater drain (not to be confused with a gully trap)
SAVE
T
DRAIN HE
FOR
RAIN
PREVENTING WASTEWATER OVERFLOWS
9
6.
WASTEWATER OVERFLOWS - PROTECTING YOUR HEALTH
Ko ngaa waipara he huarahi tuku – hei tiaki to hauora
Contact with wastewater can cause diarrhoea, and more
serious diseases like cholera, typhoid, and dysentery.
When Council is aware that an overflow has affected a
waterway or the harbour, health warning signs will be put
out in prominent locations, and the media is advised. If
you see health warning signs or you think an overflow has
occurred there are a few things you can do to minimise
the health risk to you and your family:

Do not swim, fish or gather shellfish if health
warning signs are in place.
 Minimise
skin contact with sewer water, especially if you have cuts and sores. Keep them clean
and covered.
 Do
not allow children or pets to play in areas contaminated by sewage overflows.
Health warning sign put out following an overflow
 Do
not eat or drink anything exposed to the sewer water, including vegetables from your garden.
 Keep
contaminated objects, water and hands away from your mouth, eyes and nose.
 Wash
hands immediately following contact with sewer water or contaminated objects or surfaces.
Following heavy rain water may not be healthy due
to contamination washed off the land.
Contamination may come from industrial sites, roads,
farms, etc. It is common for elevated bacterial levels to be
recorded in waterways after heavy rain.
Harbour waters may be unsafe after periods of heavy rain
OMMENDED
C
E
R
E
R
A
YOU
IM IN THE
NOT TO SW
S
R 48 HOUR
O
F
R
U
O
B
HAR
VY RAIN.
AFTER HEA
10
BEST PRACTICE GUIDELINES FOR STORMWATER POLLUTION PREVENTION
7.
HOW YOU CAN PREVENT BLOCKAGES AND OVERFLOWS
Pehea te whakakore purunga, maringi noa ranei o te wai
There are a few simple things you can do to prevent
causing a blockage or overflow:
Do not flush these!
Condoms
Sanitary products
Rubber gloves
Medical wipes

Place a waste basket in your bathroom to dispose
of solid and inorganic waste. Disposable nappies, condoms and personal hygiene products do not belong in the sewer system. These need to go into
your domestic rubbish.

Collect fat, oils and grease in a container and
dispose of it in the rubbish bin or bury it in
the garden.

Start a compost pile or worm farm for food scraps.

Take inorganic rubbish to your local refuse station.

Put baskets/strainers in sink drains to catch food scraps and other solids.

Before you plant trees, check how big they are expected to grow and place them in a suitable area away from pipes.

Ensure your gully trap is legal (contact Council to
check this if you are unsure). If you didn’t do it – don’t flush it
Mena kare koe i tuku, kaua e tukuna
These are some of the more interesting items
that have caused blockages in sewer lines:
Dental floss
Disposable nappies

An entire deep fryer

Dead animals

Doormats

Wigs

False teeth

Large rocks

Blocks of wood
PREVENTING WASTEWATER OVERFLOWS
11
COUNCIL RESPONDS TO BLOCKAGES AND OVERFLOWS
8. HOW
He aha ngaa huarahi a te Kaunihera hei whai atu i ngaa purunga, maringi
noa ranei o te wai
Once a blockage or overflow has been reported to Council
our contractors will come and assess the problem and
find the quickest way to fix it. This may involve flushing
a sewer line to clear a blockage, diverting wastewater,
inspecting pipes using a camera and even digging up
pipes to repair them. Council will investigate what caused
the problem so we can prevent it from occurring again.
If it’s a blockage in the public pipes, we will fix it. If it’s a
blockage on your property, the expense and responsibility
is your's and you will need to hire a plumber.
If there has been an overflow to public areas or the
stormwater system Council will clean up any mess and
disinfect the area. This may involve using vacuum tankers
(sucker trucks) to collect wastewater. If wastewater
has flowed into waterways or the harbour it may not be
possible to remove all of the contaminated water.
Vacuum tanker removing contaminated water from a stormwater pipe
Council will put up health warning signs if there is a
possible health risk and advise the media and any
affected parties. Council will take water samples to check
water quality and as soon as it’s safe will advise the
public and remove the health warning signs.
Water quality sampling following a sewer overflow
IF Y
WASTE OU NOTICE
A
WATER
O
V
E
RF
CALL C
OUNCI LOW
IMMED
L
IATELY
ON 57
7-700
0
12
BEST PRACTICE GUIDELINES FOR STORMWATER POLLUTION PREVENTION
Marathon 53918