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4.0
Subsurface Foundation Requirements
4.1
Foundation Requirements
The soil on which the HydroStor system is constructed must have adequate bearing capacity to
support the system. The native soils must be able to maintain the bearing capacity when water has
infiltrated into the subsurface system as well. If there is inadequate bearing capacity of the native
soil, additional aggregate may be necessary in the foundation of the system. The foundation must
be clean, washed, crushed, angular stone placed between the subgrade soil and the bottom of the
chambers.
Increased dead load (fill) placed over top of the chamber system requires greater bearing capacity
from the subgrade supporting the system. The strength of the foundation at the bottom of the
chambers is determined by the bearing capacity of the subgrade soils and the depth of aggregate
foundation stone that is placed. The deeper the stone placed in the foundation, the more the load is
spread on the underlying subgrade allowing system installation in weaker native soils. Table 1 for
the HS75 and Table 2 for the HS180 provide the required foundation stone depth for required cover
heights and subgrade bearing capacity combinations. Refer to Figure 5 for minimum requirements
for foundation depths and chamber spacing.
If soils with a bearing capacity of less than 2.0 ksf are encountered, a geotechnical engineer should
evaluate the site conditions and make recommendations for installation of the system and required
foundation preparation.
Cover
Height (ft)
4.1
4.0
3.9
1.5
6
6
6
2
6
6
6
2.5
6
6
6
3
6
6
6
3.5
6
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4
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4.5
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5
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5.5
6
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6.5
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7.5
6
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6
9
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Page 9
Table 1 – HS75 Minimum Required Stone Foundation Depth (inches)
Minimum Required Bearing Capacity of Native Soil Subgrade (ksf)
3.8
3.7
3.6
3.5
3.4
6
6
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9
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©2015 Prinsco, Inc | 800.992.1725 |
3.3
3.2
3.1
3.0
2.9
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15
www.prinsco.com
Design Guide
2.8
2.7
2.6
2.5
2.4
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12
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2.3
2.2
2.1
2.0
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05/15
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