Session DR PARTICIPANTS Handout
PARTICIPANTS NOTES
WASH DRAINAGE
This handout supplements the print out of the powerpoint, for additional information
The intention of the Drainage Module is to cover in a short time (half a day, 3.5 hours max.)
the principles of drainage in emergencies; the module is designed to show
1. What are the main causes of excessive water in an emergency
2. What are the dangers caused by this water
3. What are the principle options for drainage
4. What are the influencing factors for these options
5. How to make a design for the main drainage options
The following information will assist with the exercises:
DRAINAGE OPTIONS EXERCISE
In your group each person chooses one drainage option below
Champion your drainage solution and debate amongst the group;
•
•
•
•
•
•
The pros and cons of the drainage option
When would you use this solution?
OUTLET TO WATERCOURSE
INFILTRATION TRENCH
EVAPORATION PANS
SOAKAWAY
OPEN CHANNEL
PIPES/SEWERS
Session DR PARTICIPANTS Handout
SOAKAWAY DESIGN EXERCISE
Task: Calculate the dimensions of a soakaway pit to drain wastewater from a
communal shower area.
A. In your groups, list the information you need to be able to do the calculation
B. Make your assessment (ask your trainer the questions)
C. Perform the calculation
Wastewater drainage infiltration rates in different soils
Infiltration rate (l/m2/day or mm/day)
Soil type
Description
Clean water
Wastewater
1,500 – 2,400
50
Moist soil sticks
together but will not
form a ball
720 – 1500
33
Loamy sand and
sand
Moist soil forms a
ball but still feels
gritty when rubbed
between fingers
480 – 720
24
Loam, porous silt
loam
Moist soil forms a
ball which easily
deforms and feels
smooth between
fingers
240 – 480
18
Silty clay loam and
clay loam
Moist soil forms a
strong ball which
smears when rubbed
but does not go
shiny
120 – 240
8
Clay
Moist soil moulds like
plasticene and feels
very sticky when
wetter
Gravel, coarse and
medium sand
Moist soil will not
stick together
Fine and loamy sand
24 – 20 Unsuitable for
infiltration systems
From Reed R, Dean PT (1994). Recommended methods for the disposal of sanitary wastes
from temporary field medical facilities. Disasters 18:4. (Table 4.3 in Harvey, Bahri & Reed
2002)
Session DR PARTICIPANTS Handout
CASE STUDIES
SCENARIO 1:
•
A site has been selected for 40,000 refugees who have crossed a mountainous
border in Eastern Europe. The refugees are fleeing ethnic persecution and although
many normally have a reasonable standard of living in cities have had to make long
arduous walks across the mountains, carrying all their possessions. Some are from
rural areas and carry stoves and some food.
•
The area has cold (-20o C) and snowy winters are followed by spring rains and hot
summers. It is April and the camp is being prepared for the imminent arrival of the
refugees in a few days.
•
The site is on the edge of a wide river valley, a large river flows through the valley
floor, the valley is mainly used for farming, on the edge of the river plain is an
existing village which uses shallow wells as a water supply. The proposed camp lies
just above the village, at the foot of a steep mountain chain, the camp is situated
about 40m in height above the river, the awesome rocks of the mountain rise above
a steeply sloping naturally wooded area which is above the camp.
•
The soil in the valley is rich alluvium clay, where the camp is it is rocky, as the site
was formerly a municipal refuse (garbage) dump for building and non hazardous
materials, it is recently been used for sheep herding. Under the surface is fissured
and fractured limestone with dry ephemeral (sometimes flowing) stream valley on
either side of the site.
•
Assume all other standard camp services are met by other agencies, apart from fuel
for cooking which is being discussed. The camp is being planned with a typical
services for a high profile emergency such as road systems, hospitals, schools,
kitchens, warehouse, tents, it is steep at 1:10 (10%) slope. Agencies can be
supported by International forces with extensive range of vehicles, machines and
gravel.
•
Make a preliminary drainage strategy, make reasonable assumptions if the
information is not to hand, be prepared to present your plan and assumptions. What
are the most likely drainage problems, what do you propose as the solutions?
Session DR PARTICIPANTS Handout
SCENARIO 2:

Following a devastating earthquake in the Caribbean early in the year. Numbers of
casualties and those affected were estimated to be 1.2m families homeless and
230,000 deaths. The worst affected areas included the capital itself, A revised
Emergency Appeal was issued to assist 80,000 families living in self settled camps
within the capital.

12,000 people have self settled a piece of wasteland behind a car dealership. They
have organised themselves with an elected committee and zone representatives.

The site is very compact with self made shelters squashed together with minimal free
space.

Pit Latrines have been constructed revealing a variety of soil profiles; broken down
garbage, mixed loam, sand and clay. The latrine on the highest point encountered
water at 1m deep, but this appears to be a localised problem or a burst water main.

The climate is exceptionally hot and humid, dust still lingers in the air after the
earthquake with danger of aftershocks, an intense rainy season is expected shortly to
arrive in May, in late summer the region is often hit by severe hurricanes.

An existing surface water drainage pipe (buried, 1m diameter) crosses the site, some
manholes have open grates leading to this pipe. The vast piles of garbage lying in the
site are being regularly cleaned away.

Make a preliminary drainage strategy, make reasonable assumptions if the
information is not to hand, be prepared to present your plan and assumptions. What
are the most likely drainage problems, what do you propose as the solutions?
Session DR PARTICIPANTS Handout
Reference List

Adams J. (1999)
Managing Water Supply and Sanitation in Emergencies, Chapter 12,
Oxfam Publications GB, Oxford

Davis J. and Lambert R. (2002) Engineering in Emergencies: A practical guide for relief
workers, Chapter 8, ITDG, London

Sphere Project: (2004) Humanitarian Charter and minimum standards in disaster response,
chapter 2, section 6 Drainage, Appendix 1 section 6 Drainage, Oxfam Publishing

WHO (1991) Surface Water Drainage for Low-income countries, Geneva: World Health
Organisation

Corsellis T and Vitale A (2005)
Oxfam Publishing
Transitional settlement for displaced populations,