5.4.12 Minimal Excavation Foundations

5.4.12.1 BMP Description

Minimal excavation foundations (BMP T5.19 in Volume V, Chapter 11 of the Ecology Manual) are defined as those techniques that do not disturb, or minimally disturb the native soil profile within the footprint of the structure. Pin foundations are an example of minimal excavation foundations.

5.4.12.2 Performance Mechanisms

By minimizing the disturbance and compaction of the soil, the hydrologic properties of the native soil are preserved.

5.4.12.3 Applications and Limitations

Minimal excavation foundations can be used to partially or completely achieve the LID Performance Standard associated with MR #5: On-site Stormwater Management, and the flow control standard associated with MR #7: Flow Control (Table II-5.16).

Table II-5.16. Minimal Excavation Foundation Applicability.

BMP	MR #5: On-site Stormwater Management		MR #6: Runoff Treatment				MR #7: Flow Control
	List	LID Performance Standard	Basic	Enhanced	Oil Control	Phosphorus
Minimal Excavation Foundation		X					X

5.4.12.4 Minimal Excavation Site Considerations

Foundations can be used in conjunction with downspout dispersion (Vol II–5.4.4 Dispersion BMPs) to receive further modeling credit.

5.4.12.5 Design Information

See the Runoff Model Representation modeling requirements in BMP T5.19 in Volume V, Chapter 11 of the Ecology Manual.

5.4.12.6 Minimum Construction Requirements

To minimize soil compaction, heavy equipment, including pile driving equipment that would degrade the natural soil profile’s ability to retain, drain and/or filter stormwater, cannot be used within or immediately surrounding the building. Tracked equipment weighing 650 pounds per square foot or less is acceptable.

5.4.12.7 Operations and Maintenance Requirements

There are no operations and maintenance activities specific to minimal excavation foundations. If used in conjunction with other BMPs, like downspout dispersion or post-construction amended soils, see the maintenance requirements associated with those.