Sanitary Sewer System
Maintenance Assessment
& Countermeasures
creating a brighter future together
SANITARY SEWER SYSTEM MAINTENANCE
ASSESSMENT & COUNTERMEASURES • FRONT COVER
Our story so far
Our philosophy
At KGC (Kyokuto Giko Consultant), we care for people and the
environment around us. Our aim is to create a healthier, brighter
future by offering - through intensive research - innovative and ecofriendly solutions to protect our planet, its people and the natural
environment.
> Our vision
Our vision is to provide original, resourceful solutions, which offer simplicity, ingenuity and
long-term reliability, anywhere in the world.
> Our values
KGC has always been actively involved in protecting the environment. The management
team at KGC is fully committed to the research, development and promotion of methods
that would minimize the impact of noise and dust, while reducing power consumption and
drastically cutting CO2 emissions, to ensure minimum adverse effects on the environment.
> Our quality assurance
To guarantee the quality control of our Management System and also to reflect our concern for
environmental issues, KGC has gained ISO 9001 : 2000 and ISO 14001 : 2004 (Registration
Numbers MSA-QS-369 and MSA-ES-133).
We constantly monitor our quality performance in order to improve the effectiveness of our
Quality Management System and to research and develop new eco-friendly methods, to
ensure customer satisfaction.
SANITARY SEWER SYSTEM MAINTENANCE
ASSESSMENT & COUNTERMEASURES • PAGE 1
Sewer System Inflow & Infiltration
What is inflow & infiltration?
These terms are used to describe the way that unmetered water - including stormwater, groundwater and
surface water - enters into sanitary sewer systems. Inflow refers to clear water from rain and snowmelt that
improperly drains into sanitary sewer systems. Infiltration refers to groundwater that leaks into sanitary
sewer systems through cracked or faulty sewer pipes.
At KGC, we investigate the causes of, and offer effective countermeasures for, inflow and infiltration. Water
that infiltrates sanitary sewer systems lowers the purifying efficiency of wastewater treatment plants, has
an adverse effect on pipeline facilities and pumping stations, and can lead to sanitary sewer overflows.
What are the problems caused by inflow & infiltration?
1>
Higher Purifying Costs
Purifying costs rise due to the decrease in water quality when normal treatment levels are exceeded at
wastewater treatment plants.
2>
Sediment Blockage
Sediment flows into pipes causing deposition and blockage, which then triggers roadway collapse.
3>
Degradation of the Living Environment
Wastewater may overflow from manholes during rainfall and cause degradation of the living environment
in various ways (odor, disease).
Types of infiltrating water
> Infiltrating stormwater
Water that infiltrates in the short term
during rainfall
> Directly infiltrating water
Water that enters into sanitary sewer systems
through improper connections or infiltrates
through manhole cover holes
> Indirectly infiltrating water
Water that flows in from spots of poor
watertightness
> Constantly infiltrating water
Water that is affected by seasonal changes
and rainfall but generally infiltrates steadily
(groundwater that exceeds the level of sewer
lines, water from drainage channels, water
from storage, etc.)
> Infiltrating service water
Water that leaks out of the water supply
> External seepage water
Exfiltration
> Illegal unmetered wastewater
Inconstant and unauthorized discharge,
unlicensed factory discharge, etc.
SANITARY SEWER SYSTEM MAINTENANCE
ASSESSMENT & COUNTERMEASURES • PAGE 2
> Our solution
Flow Rate Survey Advice
At KGC, we conduct a flow rate survey in order to determine the causes
of water inflow/infiltration. To do so accurately, we first define a
survey area in the community (approximately 10 to 30 hectares) and
then subdivide this area into several block divisions according to
purpose and type of inflow/infiltration.
> Our survey, a positive approach
The Merits of a Flow Rate Survey
Appropriate Countermeasures
After conducting a flow rate survey, KGC determines the
appropriate countermeasures based on the causes of
inflow/infiltration.
Identifying Areas of High Risk
It would be inefficient and expensive for municipalities to
attempt to conduct surveys over wide areas to determine
the causes of water inflow/infiltration.
Therefore, KGC advises to first conduct a flow rate survey
in smaller areas in order to narrow down the number of
zones where there is high risk.
SANITARY SEWER SYSTEM MAINTENANCE
ASSESSMENT & COUNTERMEASURES • PAGE 3
Flow Rate Survey Process
Collection of Materials
Gather information on the present condition of pipes
Collect sewerage plans and related information
Division by Blocks
Define block divisions for targeted districts
Flow Rate/Rainfall Measurement
Measure flow and determine positioning of rainfall meters
Install flowmeters and rainfall meters
Determine the Volume of Stormwater
Inflow/Infiltration
Ascertain quantitative values from flow rate surveys and determine
the precise causes of stormwater inflow / infiltration
Inflow & Infiltration Avoidance Measures
Evaluate sewer pipe capacity when in use
Determine order of priority in detailed plans and review
content of work for each block
SANITARY SEWER SYSTEM MAINTENANCE
ASSESSMENT & COUNTERMEASURES • PAGE 4
How We Do It
> Countermeasures
The KGC inflow and infiltration countermeasures planning process is shown as follows.
> Detailed Survey
The following methods are used for investigation.
Countermeasures for Inflow
& Infiltration Resulting from Stormwater
Facility
High Groundwater Level
Low Groundwater Level
Wastewater Facility
Inspect
Manhole Cover
Visual Check
Countermeasures
for Constantly
Infiltrating Water
n/a
n/a
Visual Check
Smoke Test
n/a
Public Inlet
Visual Check
Check for Exfiltration
n/a
Lateral Sewer
T V Camera Survey
Check for Exfiltration
n/a
Street Gutter
Main
n/a
TV Camera Survey
Manhole
n/a
Visual Check
> Our recommendation
Countermeasures for Infiltrating Stormwater
It is extremely difficult to completely eliminate infiltrating stormwater. Peak cut and
peak equalization measures are what we recommend.
KGC determines the ratio between the amount of wastewater and the amount of
stormwater, sets “reduction targets” and offers effective measures.
SANITARY SEWER SYSTEM MAINTENANCE
ASSESSMENT & COUNTERMEASURES • PAGE 5
The Process
On-site Countermeasures
Private Sewer System
Sanitary Sewer System
Construction of Stormwater
Drainage & Retention Facilities
Countermeasures for Constant Infiltration
After conducting a survey to determine the causes of constant water infiltration,
KGC offers various solutions to repair or reconstruct sewer pipes when there is
groundwater infiltration.
Countermeasures for Illegal Unmetered Wastewater
To deal with illegal unmetered wastewater, after identifying the targeted
pipes through block division, KGC carries out visual checks and TV camera
surveys to specify the causes, and then offers appropriate countermeasures.
> Our conclusion
In order to build a safe and sustainable society, it is critical to
reduce the environmental load caused by construction and public
works. At KGC, we offer clean solutions for effective and efficient
maintenance management of water and wastewater systems to
preserve the present and create a brighter future.
SANITARY SEWER SYSTEM MAINTENANCE
ASSESSMENT & COUNTERMEASURES • PAGE 6
Kyokuto Giko Consultant Co., Ltd.
> Tokyo Office
Motoasakusa MN Bldg., 1-6-13 Motoasakusa, Taito-ku, Tokyo 111-0041, Japan
> Corporate Headquarters Office / Engineering Development Department
Far East 21 Bldg., 2-3-26 Minamikaneden, Suita-City, Osaka 564-0044, Japan
Tel: +81-3-3841-6137
Fax: +81-3-5806-1085
www.kgc21.co.jp/brighter-future
creating a brighter future together
SANITARY SEWER SYSTEM MAINTENANCE
ASSESSMENT & COUNTERMEASURES • BACK COVER