UNDERGROUND DETENTION SYSTEMS

Detention Systems manufactured with Corrugated Steel Pipe exceed all performance criteria. CSP Systems are economical, adaptive, structurally sound and durable. No other method for containing storm water runoff can achieve the results obtainable with Corrugated Steel Pipe Detention Systems. Southeast Culvert, Inc. can assist with the design and layout of your next detention system.

Foundation and Bedding

Prior to placing any bedding the foundation should be uniform and stable. Any unsuitable foundation material shall be removed. At a minimum 4 inches of a well-graded granular material shall be placed as the bedding (#57 stone or similar if there is no suitable on site material).

Backfill

The backfill material shall be an A1, A2 or A3 granular fill per AASHTO M-145, some local soils may meet the material requirements but should be approved by the engineer or geotechnical engineer. The material shall be placed in equal lifts and compacteto minimum 90% AASHTO T99 standard proctor density. The backfill should be carefully placed and compacted under and around the pipe haunches.

The backfill should be placed evenly on both sides of the structure and advanced along the pipe length at the same rate to avoid differential loading. At a minimum, larger, multiple barrels and more critical structures should have stone or a uniform graded material, not larger than ½ inch in size, placed for the initial 1.5 to 2 feet up the pipe elevation or to the spring-line elevation of the pipe. A separation geotextile fabric is to be placed above and below this initial fill material.

Minimum Cover

Cover should be placed to the proper elevation as outlined in the plans. Construction loadings need to be determined based on the type of equipment planned to be used during construction.

Minimum cover for construction equipment is different than standard vehicle loadings and should be carefully assessed prior to placing any equipment on the structure. Follow the chart as outlined in the NCSPA

Installation Guidelines:

Minimum Cover for Construction Loads

 

 

Pipe Span, in

 

 

18 – 50 kips

 

 

50 – 75 kips

 

 

75 – 110 kips

 

 

110 – 150 kips

 

 

12-42

 

 

2.5 ft

 

 

2.5 ft

 

 

3 ft

 

 

3 ft

 

 

48-72

 

 

3 ft

 

 

3 ft

 

 

3.5 ft

 

 

4 ft

 

 

78-120

 

 

3 ft

 

 

3.5 ft

 

 

4 ft

 

 

4 ft

 

 

126-144

 

 

3.5 ft

 

 

4 ft

 

 

4.5 ft

 

 

4.5 ft