Site Design - Class 12: Group of bldgs, water, ramps

Benchmark

an elevation that has already been agreed upon, marked with brass pins, hammered on sidewalk

field mark

establishes a 0 elevation mark on a local site, often done on a tree that’s not cut down that can be readily seen

storm water addresses…

• too much water: detention

• too dirty water: retention

  or BOTH

2 (interrelated) problems with Retention of dirty water

1. impervious cover

2. mom-point source pollution

Retention

to hold polluted water out of the system

example: retention ponds

“if its always wet, its ______”

Retention!

Detention

to restrain the speed of storm water entering system

For schematic sizing detention/retention, __% of site area OR _% of pervious area (whichever’s largest) are good rules of thumb

10%

25%

detention basins are used for sites over ___ acres (bigger sites)

10

Infiltration basins are used for ___ sites

smaller

small site infiltration

infiltration trench, aka rain garden - can grow to be a bio-swale

storm water management is required on sites greater than __ acre

1

BUT local codes may be stricter & circumstantial