1. Storm Water Storage and Treatment
Civil Engineering and Architecture
Unit 3 – Lesson 3.4 – Site Considerations
STORM WATER STORAGE AND TREATMENT
Code Requirements
Often a storm water management system is required to
Restrict storm water runoff rate pre- development levels (quantity)
Treat storm water so that runoff is relatively clean and free of toxins (quality)
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2. Storm Water Management Devices
Storm Water Storage and Treatment
Civil Engineering and Architecture
Unit 3 – Lesson 3.4 – Site Considerations
Storm Water Management Devices
Retention Pond (Wet Pond)
Collects storm water in a permanent on-site pond
Treats storm water by allowing pollutants to settle out or be removed by biological action
Water can be reused for irrigation
Limitations
Difficult to maintain in arid and semi-arid climates
Project Lead The Way, Inc.
Copyright 2010

3. Storm Water Management Devices
Storm Water Storage and Treatment
Civil Engineering and Architecture
Unit 3 – Lesson 3.4 – Site Considerations
Storm Water Management Devices
Detention Pond (Dry Pond)
Extended detention basin that collects storm water and then slowly releases the water into the municipal storm water system
Treats storm water by allowing pollutants to settle out
Limitations
Drainage area should be at least 10 acres, otherwise small release pipes clog
Project Lead The Way, Inc.
Copyright 2010

4. Storm Water Storage and Treatment
Civil Engineering and Architecture
Unit 3 – Lesson 3.4 – Site Considerations
Detention Pond
Retention Pond
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Copyright 2010

5. Detention and Retention Pond Design
Storm Water Storage and Treatment
Civil Engineering and Architecture
Unit 3 – Lesson 3.4 – Site Considerations
Detention and Retention Pond Design
DETENTION CAPACITY
This slide illustrates structural differences between detention and retention ponds. A detention pond will allow a slow discharge of water (not to exceed the pre-development discharge) through piping at the bottom of the pond. This allows the pond to eventually empty after a storm.
A retention pond maintains a permanent pool of water. Water is not drained from the pond; however, water can slowly infiltrate the soil.
Both retention and detention ponds provide an overflow structure to allow controlled release when the pond capacity is exceeded.
Courtesy DoD.
Project Lead The Way, Inc.
Copyright 2010

6. Storm Water Management Devices
Storm Water Storage and Treatment
Civil Engineering and Architecture
Unit 3 – Lesson 3.4 – Site Considerations
Storm Water Management Devices
Underground Storage Tanks
Variation of the detention pond
Detains water for short periods before releasing it into municipal storm water system
Limitations
Expensive but can be used for smaller drainage areas
Project Lead The Way, Inc.
Copyright 2010

7. Storm Water Management Devices
Storm Water Storage and Treatment
Civil Engineering and Architecture
Unit 3 – Lesson 3.4 – Site Considerations
Storm Water Management Devices
Storm water Wetlands (Constructed Wetlands)
Storm water diverted to a permanent pool that incorporates wetland plants
Pollutants removed through settling and biological activity
Limitations
Drainage area should be at least 25 acres
Difficult to maintain in arid and semi-arid climates
Project Lead The Way, Inc.
Copyright 2010

8. Storm Water Storage and Treatment
Civil Engineering and Architecture
Unit 3 – Lesson 3.4 – Site Considerations
Constructed Wetlands
The image on the left is a subsurface flow constructed wetland (i.e., the water flows through a permeable layer below the surface, often soil, sand, or gravel). Free water surface systems like the one shown on the right are designed to simulate a natural wetland with shallow water flowing over the surface. This image shows constructed wetlands on a site formerly used as a dump in Orlando, Florida.
Courtesy EPA
Courtesy EPA
Project Lead The Way, Inc.
Copyright 2010

9. Size of Storm Water Ponds
Storm Water Storage and Treatment
Civil Engineering and Architecture
Unit 3 – Lesson 3.4 – Site Considerations
Size of Storm Water Ponds
Rule of thumb: Reserve ten percent of development area for storm water pond
Volume of storm water estimate
V= Volume of storm water in acre feet
A = Drainage area (area of site) in acres
Project Lead The Way, Inc.
Copyright 2010

10. Size of Storm Water Ponds
Storm Water Storage and Treatment
Civil Engineering and Architecture
Unit 3 – Lesson 3.4 – Site Considerations
Size of Storm Water Ponds
Area of pond
Ap= Area of pond
V = Storm water volume in acre ft
d = Average depth of pond
Project Lead The Way, Inc.
Copyright 2010

11. Storm Water Storage and Treatment
Civil Engineering and Architecture
Unit 3 – Lesson 3.4 – Site Considerations
Pond Forms
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Copyright 2010

12. Size of Storm Water Ponds
Storm Water Storage and Treatment
Civil Engineering and Architecture
Unit 3 – Lesson 3.4 – Site Considerations
Size of Storm Water Ponds
Considerations:
Soil characteristics
Volume of water
Contamination level
Depth to water table
Topography of site
Project Lead The Way, Inc.
Copyright 2010