09 Habitat for Humanity Yelm - Infiltration Verification Testing Memo
Tumwater, WA SageGeotechnical.com
March 4, 2025
Transmitted via email to: ben@spshabitat.org
South Puget Sound Habitat for Humanity
P.O. Box 2225
Olympia, WA 98507
Attn: Ben Fransua, Director of Construction
Re: Verification Testing Services
Yelm Planned Residential Development
Yelm, Washington
Sage Project No. 052002
Dear Mr. Fransua:
At the request of South Puget Sound Habitat for Humanity (SPS Habitat, project owner), Sage
Geotechnical, LLC (Sage) completed verification testing in support of the Yelm Planned
Residential Development project. The results of the verification testing are summarized herein.
PROJECT UNDERSTANDING
SPS Habitat is developing a 2.3-acre parcel located at 407 Longmire Street Northwest in Yelm,
Washington (site). The City of Yelm has required verification testing of two existing
stormwater infiltration ponds. The approximate locations of the ponds are shown on
Attachment 1.
VERIFICATION TESTING
The stormwater pond in the western half of the site has a 300-square-foot (sf) base and 3
horizontal to 1 vertical side slopes partially vegetated with grass. The stormwater pond in the
eastern half of the site has a 200-sf base with gentle slopes covered in mulch.
On February 27, 2025, Sage completed verification tests of the two stormwater ponds. Testing
was completed in accordance with the U.S. Environmental Protection Agency’s (EPA) falling
head percolation test procedure. The test procedure and locations were selected by LDC, Inc.
(project civil engineer).
The verification tests included multiple trials; during each trial, 6 inches of water was
infiltrated into the base of the pond. The trials were repeated until they yielded similar
infiltration rates.
Yelm Planned Residential Development
March 4, 2025
2 SageGeotechnical.com
March 4, 2025
Infiltration rates were calculated in accordance with the EPA’s falling head percolation test
procedure. This procedure does not include correction factors or factors of safety. Sage
calculated a field infiltration rate of 15.8 inches per hour for the western pond and 9.6 inches
per hour for the eastern pond.
CLOSING
We trust that this letter provides you with the information needed to proceed with the project.
If you have questions or comments, please contact the undersigned at
lancel@sagegeotechnical.com.
SAGE GEOTECHNICAL, LLC
Lance Levine, PE
Senior Geotechnical Engineer
LGL/MCS/DCS
[HTTPS://SAGEGEOTECHNICAL.SHAREPOINT.COM/SITES/SAGEGEOTECHNICAL/SHARED DOCUMENTS/PROJECTS/052 SOUTH PUGET SOUND HABITAT FOR
HUMANITY/002 YELM PLANNED RESIDENTIAL DEVELOPMENT/R/YELM PRD VERIFICATION TESTING LETTER 3.4.2025.DOCX]
Attachments: Attachment 1. Plan Sheet DR-01
ATTACHMENT 1
Plan Sheet DR-01
ROAD A
DRYWELL TABLE
12/18/2023
Expires
Approved for Construction
Civil Review Engineer
Reza R. Roukerd
7/23/2023
Infil-1
Infil-2