Technical Bulletin 19-09

1. Technical
Bulletin 19-09
Setting basement floor elevation
above the groundwater table (SHWT)
in residential construction

2. WHY?
• Protect the homeowner
• Protect adjacent properties

3. Which Plan Types?
Single-family dwellings:
• Infill Lot Grading Plans,
• Conservation Plans (CON),
• Bonded Lot Grading Plans
(SDGP/SPGP)
• Rough Grading Plans (RGP)

4. Which Plan Types?
Townhouses:
• Site Plans (SP),
• Rough Grading Plans (RGP),
and
• Bonded Lot Grading Plans
(SPGP).

5. WHEN does it apply?
• When a Soils Report is already
required (Class III and IV
problem soils)

6. Determine Seasonal High Water Table (PFM)
•Direct Observation November through May, should not
use during June through October unless the value of the
Palmer Drought Severity Index is > 2.0 (i.e., wet).
•Soil morphology can be used throughout the year by a
certified / licensed professional

7. FREEBOARD
Case 1
Sump Crock
2.5 ft.
• No groundwater mitigation req’d
• Std. perimeter underdrains
connected to a sump
• Include foundation drain details
on civil plans
Freeboard > 2.5 feet
SHWT

8. 2.5 ft.
Case 2
Sump Crock
FREEBOARD
Freeboard 1 to 2.5 ft.
• Raise basement to Case 1. If not
feasible but topo allows for gravity
outfall, install U/D system
connected to a structure in gravity
storm drain or gravity outfall.
• If still not feasible install dual sump
pump system with backup power
SHWT

9. • Try to raise the basement or lowest
FF to Freeboard > 2.5 ft.
• If still not feasible, use crawl-space
or no basement
Case 3
Sump Crock
2.5 ft.
Freeboard < 1 ft or
SHWT above basement /lowest FF
• If not feasible, raise
basement or lowest FF to
Case 2 (gravity outfall)
NEGATIVE
FREEBOARD
SHWT

10. Technical
Bulletin 19-09
QUESTIONS?