09/03/2004/Apinya/KMUTTarc354Site Drainage1 SITE DRAINAGE Storm drainage system Grading procedure Factors influencing drainage system surface drain subsurface

09/03/2004 /Apinya/KMUTTarc354Site Drainage 1

SITE DRAINAGEStorm drainage system

Grading procedureFactors influencing drainage

systemsurface drain

subsurface drain


Storm drainage system

In grading, SURFACE RUNOFF is the primary method to remove excess water. This is usually in some form of STORM DRAINAGE SYSTEM, which collects, conducts and disposes excess surface water caused by runoff from rainfall.


A storm drainage system is designed to:

COLLECT CONDUCT DISPOSE


Private system

Public system

collect

collect

conduct

Dispose


A storm drainage system can:

1. Safeguard against erosion by reducing the rate of flow and volume of water

2. Reduce flooding and damage to property and construction

3. Increase useable area 4. Eliminate unnecessary standing water which may lead

to pollution and breeding of insects.5. Provide better growing condition for plants by

reducing soil saturation (soil contains too much water lack of oxygen)

6. Improve load-bearing capacity of soils, thereby increasing the build-ability of a site.



Good Drainage practice

1. Design the grading and drainage plan as to respect, reinforce, and duplicate the existing natural systems.

2. New runoff must never be purposefully redirected from one property onto neighboring property.

3. Surface drainage is generally preferred to underground systems for two reasons: cost and ecology.

4. Avoid the design of a system that necessitates the drainage line through a foundation or under slab.



5. Always consider some method to slow runoff water down and let it be absorb into the soil.

6. Slow-moving water will create a bog, while water moving too fast create erosion and unwanted gullies.

7. Paved areas (parking, sport court, etc.) look better when graded almost level-- avoid wildly sloping paved area.

8. Avoid draining large amounts of water from paved areas across pedestrian paths or sidewalk. Install a catch basin or trench drain to collect most runoff before the sidewalk.

9. Always design a secondary drainage route to handle runoff in case of the primary one become clogged.

Good Drainage practice(Continue).



Grading procedure 1.Topographic

characteristic and natural drainage pattern.

2. Locate unusual soil type -- sandy soil, clay.

3. Fixed elevations or points on the site such as roads, trees, adjacent buildings

4. All area that need to be kept dry and elevations

5. The location and extent of the existing sewer system (both public and private system)



Factors which determine drainage needs are: 1. LAND USE --urban or rural area, function, density

and how fast we must drain the water. 2.TOPOGRAPHY --the steeper the area, the faster

draining it will be, drainage must be provided above and below steep bank

3. SIZE OF AREA TO BE DRAIN -- determines the size of underground and surface structure. Typically, the larger the area, the larger the underground structures or surface ditches.

4. TYPE OF SOIL -- determines the rate of percolation or amount of water the soil will absorb.

5. VEGETATION -- any thick, matty ground cover will slow down the rate of runoff and reduce the need for elaborate drainage systems.

6. INTENSITY OF RAINFALL -- amount of water from rainfall will affects the type of drainage system .

Grading procedure (*factors)


Most use areas -- play fields, courts, patios, roof garden, etc. require a dry level surface. Level area do not drain well, so we must TILT all use areas slightly to allow water to runoff.

REMEMBER to set the building finish floors at least 15 cm. Higher than the outdoor elevation.

Surface drain: Draining level area

Sloping plane

Sloping plane with valleyFunnel system(+subsurface drainage)


Cut or fill slopes will be erosion. Therefore, must be drained properly with interceptor ditches or terraces. The ditch will carry water to some collection point for dispersal. Ditches constructed in cut areas will usually function without a lining, while those in fill may require a concrete or asphalt lining.

Surface drain: Drainage of steep slope


Subsurface drainage: 1. Area drain

located at the lowest point in the drainage basin, looks somewhat like a large shower drain.

2. Catch basin

like area drain except it has a deep pit to catch sediment and keep it from clogging the pipes.

3. French drain (Trench drain)

a linear drain to collect water along the length

4. Culvert

A pipe under driveways, paths, etc.5. Underground pipe

pipe used to transport runoff from the collection to distribution.


The closed system is useful in level areas. This method is useful for a variety of specialty problems including: athletic fields or golf course which avoid dangerous catch basins on the field, The cost is expensive.

Subsurface drainage:

The perforated pipe is installed at the bottom of the gravel with the holds point up. Water fills the gravel and eventually pours into the holds where it can be taken away.

This discharge water by gravity through a perforated pipe laid on gravel with the holds pointed down.


Natural system used in natural area where

area drain is needed Herringbone system

two way tilt area Gridiron system Interceptor system

Depth of underground pipe should be between 75 cm. To 150 cm. Slope of main pipe should be 2-3% max. minor pipe can be at 0.25 minimum.

Subsurface drainage: typical sub-drain layout


Drainage system : exampleSource:Michigan Soil Erosion & Sedimentation Control Guidebook

Surface Drainage System: Enclosed Underground Drainage System:


Enclosed Underground Drainage with On site storage

Drainage system : example

Combination Drainage Systemwith On site storage


Drainage system : exampleSource:Michigan Soil Erosion & Sedimentation Control Guidebook


Readings 1. GRADE EASY, Prof. Richard K. Untermann,

Department of Landscape Architecture, University of Washington, Seattle. MUST READ

2. Site Planning, Environment, Process, and development, R.Gene Brooks, Prentice Hall, N.J. page 129-171

Documents

09/03/2004/Apinya/KMUTTarc354Site Drainage1 SITE DRAINAGE Storm drainage system Grading procedure Factors influencing drainage system surface drain subsurface