Envir Con. and Cont.

Question 1

Runoff

Answer 1

Stormwater that accumulates on the site in excess of what can be absorbed by the ground.

Question 2

Drainage on site

Answer 2

Any development of a site interrupts the existing drainage patterns and creates additional water flows. The proposed design must supply positive drainage away from the buildings, parking and walk areas to avoid flooding, erosion, or standing water.

Question 3

Name drainage systems and describe

Answer 3

Abovewater drainage systems: use impervious paving, sheet flow, gutters, ground swales and channels to manage runoff and direct appropriately.

Underwater drainage systems: Use perforated drains and enclosed storm sewers to carry the runoff from the site, either to a municipal storm sewer system or to a natural drainage outlet such as a river.

Question 4

Sheet flow

Answer 4

Is water that drains across a sloping surface, whether the surface is paved, grassy or otherwise landscaped.

Question 5

Storm drains

Answer 5

Collect water from roof downspouts, drain inlets, catch basins and drain tiles

Question 6

Drain inlet

Answer 6

An opening in the ground that allows stormwater to run directly into the storm sewer, The opening is usually covered with a metal grate for safety and to keep out debris.

Question 7

Catch Basin

Answer 7

an underground reservoir that has a sump built into it, debris settles into the sump instead of flowing down the sewer and potentially clogging the pipes.

Question 8

Stormwater management

Answer 8

For most paved surface req. 1.5% slope (.05% slope req. in smooth surfaces). Large storm sewer systems must have manholes for service access. Are always separate from the sanitary sewer.

Question 9

Runoff Coefficient

Answer 9

The fraction of water not absorbed

Question 10

Required drainage capacity

Answer 10

Based on the size of the area, Runoff coefficient and amount of water to be drained during most severe storm

Question 11

n-year storm

Answer 11

n = the probability a storm of that magnitude or greater will occur at this location in any given year. ex. 100-year storm has 1% probability; 25-year storm has 4% probability.
Drainage system typically designed for 25 or 10-year storms.

Question 12

Holding pond

Answer 12

collects the site runoff and releases it into the sewer system at a controlled rate, it prevents excess water from flooding other areas.

Question 13

Utilities

Sanitary sewer and storm sewers

Answer 13

Usually, take precedence in planning because they depend on gravity flow. The invert (lowest elevation) of the existing sewer must be established.

Question 14

Size and slope of sewer piping

Answer 14

The minimum slope of the building sewer is .5% to 2.0% depending on the size of the pipe. Greater slope required for smaller pipes. (pipe of 2 1/2” or less must be placed at a slope of 1/4in/ft. Pipes 3”to 6”; the slope is 1/8in/ft)

Question 15

Automobile Circulation

Answer 15

Roads should be laid out so a driver can go directly to the parking area, to a drop-off point, or to the loading area without intersecting the roads to the other areas.

Question 16

On-Site Road slopes

Answer 16

Roads should be limited to a maximum slope if 15% for short distances, although 10% or less is preferable. Roads with slope greater than 10% must have a transition of 1/2 of ramp slope.

Question 17

On-Site Road Clearances (driveway entries)

Answer 17

150ft from the public intersection (exeption could be large public spaces)
one way = 12ft min
two way = 24ft min
Cul-de-sac = 40ft radius

Question 18

Road Crown

Answer 18

A gradual cross slope at center of the roadway for drainage.