adet-wss 6pw lecturer

8/12/2019 Adet-wss 6pw Lecturer

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MINEDUC

ADET/TEVSA

P.O.BOX 3830 KIGALI-RWANDA

ADET/TEVSA-INTER-SCHOOL EXAMINATIONS

FIRST-TERM-2011

SUBJECT: WATER SUPPLY&SANITATION (WSS)

CLASS: 6th

forms PUBLIC WORKS

LEVEL: PUBLIC WORKS A2

WEIGHT: 100Marks

DURATION: 3HOURS

INSTRUCTIONS

This examination paper containsTHREE SECTIONS:

Attempt allQUESTIONS of SECTION A

AttemptANY THREE (3) QUESTIONS of SECTION B and

AttemptANY ONE (1) QUESTION of SECTION C


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Attempt ALL QUESTIONS of SECTION A: 55marks

1. What is highway drainage? (2mks)

Answer/ -it is the process of clearing surface and sub-surface water from

the highway.

2. What is the public institution in charge of road maintenance in

RWANDA? (2mks)

Answer/ -FER=fonds dentretien routier/RMF=road maintenance fund

3. Give answers by TRUE or FALSE? (4mks)

i. The serviceability of highway is very much dependent on theeffectiveness of its drainage.

ii. The highway drainage is planned after highway construction.iii. Culverts are placed in highway after its construction.iv. Highway drainage ditches are given direction according natural slope

of the region embodying the highway.

v. The place where the soil from cutting activity is deposited is calledEMBANKMENT.

Answer/ - i.TRUE; ii.FALSE; iii.FALSE; iv.TRUE; v.TRUE

4. Complete the following sentences with appropriate words (4mks)

i. In Highway, the part used by pedestrians iscalled

ii. The groundwater when it rises up, it reaches the part of highwaypavement called.

iii. Water ponding on the road surfacecauses

iv. When materials like mud and debris are deposited on hydraulicdrainage structures, they cause of them.

Answer/ -i.Footpath

-ii.sub-grade

-iii.aquaplanning or hydro-planning

-iv.clogging or obstruction


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5. Define and show the following terms by a neat sketch (6mks)

i. Kerbii. Road surfacing course

iii. CamberAnswer/ -i.kerb is the road edge used as a barrier to retain storm run-off

from the road surface and act as a structural support during pavement

construction and protect footpaths.

-ii. Road surfacing course is the layer of a road over which cars are

running and built which bituminous materials.

-iii. Camber is an upward curve given to a surface, especially of a

road to drain it on both sides.

6. Categorize highway drainage systems depending on source of water and

give the place of use for each category (4mks)

Answer/ -surface drainage system and sub-surface drainage systems

-surface drainage system is used to manage water on the highway

pavement from rainfall.

-sub-surface drainage system is used to manage water underneath

the highway pavement from water table fluctuation.


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7. What is WATER TABLE? And show it by a neat sketch (4mks)

Water table is the level below which the ground is saturated with water.

8. Explain how toilets (pit latrines) can contaminate groundwater and showthis by a neat sketch (4mks)

Answer/ -when the pit of latrine is dug below water table, the soaking

process contaminates groundwater and spring.

9. With a neat sketch, show the structure of sub-drain cross-section used in

sub-surface water control (4mks)

Answer/ -


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10. i) define Erosion? (2mks)

Answer/ -Erosion is the phenomenon that takes away the soil of fills or

mountains or cultivable land due to the rainfall or wind forces.

ii) What are the factors affecting Erosion? (State at least 5)(2.5mks)

Answer/ - soil characteristics (soil type)

- Slope of the region (length, nature: steep, slight, abrupt)- Vegetation cover(kind of)- Climate- Cultivating activity

11. State 4 ways to control erosion in highway (4mks)

Answer/ -Stabilizing excavation slope by constructing berms and counter-

berms, planting grasses and trees

- Stabilizing embankment slope by planting grasses and trees- Avoiding quarrying activities or mining near, around and along

the highway.


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- Removing unexpected slope collapse when it occurs as soon aspossible.

- Cleaning highway hydraulic structures.- Digging the deep furrows on the hill contouring the highway.

13. Mention THREE main groups of wastewater that can be generated

from various activities of RWANDESE. Give ONE example for each

(4.5mks)

Answer/ - Domestic wastewater (e.g:bathing, washing dishes &Kitchen

utensils )

- Industrial wastewater(e.g: oils, greases, metal pieces,.)- Environmental wastewater(e.g: debris from cultivation, surface

run-off,)

14. Give structural effects that can be caused by lack of highway drainage

(at least 4) (4mks)

Answer/ - Early destruction of highway pavement

- Clogging or obstruction of highway hydraulic structures.- Collapse of excavation slope- Settlement of embankment slope

15. Surface water channels are normally of triangular/trapezoidal cross-

section. What do think should be the reasons (at least 4) (4mks)

Answer/ - They are capable of carrying large volumes of water over long

distances.

- They are easy to design and maintain and long-term problemsdeveloping can be detected early.

- They are monitored by simple visual inspection from thesurface.

- These sections are more economical.


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SECTION B: Attempt any TWO (2) questions /30mks

16. with a neat sketch, show the sources of sub-surface water in the highway

(15mks)

Answer/

17. with a neat sketch, show the parts of the highway pavement and give the

role of top part in terms of surface water drainage (15mks)

Answer/

Answer/ asphaltic concrete layer is placed for preventing rainwater from

penetrating through the highway pavement.


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19. if the water table is found to very high, efforts should be made to lower

it at least 1.25m below highway pavement, with a neat sketch, show how

this can be done by use of filter drains. (15mks

20. Give 5 common types of road paved surface deteriorations due to poor

drainage of highway , their causes and remedial measures (15mks)(1mrk

saying them for each,1mrk for causes and 1mrk for remedial measures)

Answer/ -1.Dust:-this results from the loss of fine binder appregates from

the road surface. It can be controlled by sprinkling water on the road

surface ( a very short-term solution).or spraying on adhesives such as latex

emulsions or resin in water.

-2.Ravelling:This the loss of coarse aggregates from the road

surface. It can be corrected by grading or blading with addition of a binder

ton improve the road surface.

-3. Potholes: thes are caused by excessive moisture content, poor

drainage, and poorly graded soils or aggregates. They are corrected by

patching.


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- 4.Rutting: this occurs when there is high moisture content in the

road subsurface soil, resulting in longitudinal depressions left in the car

wheel paths. It can be corrected by filling with roadbed material.

-5.Corrugations or washboards: these are a series of ridges anddepressions across the road surface caused by lack of surface cohesion and

excessive vehicle speeds. They are corrected by improving the cohesive

qualities of the road surface.

-6. Cracking: this is due to thermal fluctuations on a road pavement

or structural fatigue. It can be corrected by sealing.

SECTION C: Attempt any ONE (1) question /15mks

21. Unpaved roads are common across the RWANDA, the preservation of

unpaved roads is important to rural communities of RWANDA. (15mks)

i. Give FOUR (4) advantages and TWO disadvantages of unpavedroads(6mks)

Answer/ -4 advantages of unpaved roads are:

-1.lower construction costs than paved roads.

-2.They require less equipment and skilled operators.

-3. They generate lower speeds than their paved counterparts.

-4. They generally provide links between paved collector roads.

-2 disadvantages of unpaved roads are:

-1. They require regular maintenance to keep them passable and

safe.

-2. They contribute heavily to water quality problems due to polluted

ru n-off from unpaved roads.

ii. Unpaved roads require PREVENTIVE maintenance on a regularbasis. What is the meaning of PREVENTIVE maintenance?(2mks)

Answer/ - Preventive maintenance is an operational activity carried

out before expected failures occurred. E.g.: digging furrows at upper

part of excavation slope to prevent erosion from collapsing it.

iii. Highway maintenance operations can normally be categorized asROUTINE and PERIODIC. Differentiate these TWO operations

(Give at least TWO reasons with help of an example for each)(4mks)


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Answer/ -

ROUTINE maintenance PERIODIC maintenance

1.operations need to be

undertaken once or more a year

1.operations are planned to

undertaken at intervals of severalyears or after a period of number

of years.

2. They require less skilled or

unskilled manpower and less

sophisticated equipment.

2. They require skilled or

specialist manpower and

sophisticated equipment.

3. These operations are cheap

and require simple planning.

3. These operations are costly

and require well-studied

planning.

e.g: vegetation control; clearingside drains and culverts

e.g. re-gravelling unpaved roadsor resurfacing paved roads

iv. Give TWO examples of EMMERGENCY maintenance that can beoperated on a highway due to the Problem of poor drainage.(3mks)

Answer/ - Removal of trees fallen in the roads

-removal of road slope collapses

- repairing accidentally broken paved roads(main roads)

GOOD LUCK!!


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adet-wss 6pw lecturer

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