Observations/Finding

Site Visit Report – Retaining Wall Evaluation

As requested, a site visit was conducted by AS Engineering and Consulting (ASEC) representatives Vamsi Polisetty and Ram Mogulla to meet with the retaining wall contractor, Brian Hughes, for an evaluation of the existing site conditions. The following observations were made:

Site Observations:

• Test pits were excavated along the proposed retaining wall alignment using a Kobelco SK210H excavator. A total of eight test pits were completed, with depths ranging from 4 to 6 feet.
• In the section behind lots 225 and 226, organic material mixed in with fill material was encountered to depths of up to 4 feet below the existing grade.
• Test pits behind lots 227 through 230 revealed loosely placed fill within the top 2 to 3 feet. While this material is believed to be located above the proposed retaining wall foundation elevation, remediation may be required before proceeding.
• Beyond the organic fill behind lots 225 and 226, and the loosely placed fill behind lots 227 through 230, the soil appeared to be of acceptable consistency. The more competent strata were identified through visual observation and confirmed by probing.
• However, based on recent DCP testing in these areas, a bearing capacity of 3,000 PSF cannot be assumed in its present condition. Remediation may be necessary once overburden material is removed from the retaining wall foundation and its reinforced zone.

Recommended Site Preparation Steps:

1. Erosion Control: Implement Best Management Practices (BMPs) in accordance with local regulations.
2. Clearing & Stripping:
   • Remove all vegetation, including trees, grass, brush, roots, and stumps.
   • Strip and dispose of topsoil as required.
3. Subsurface Preparation:
   • Remove any existing buried structures, organic laden fill, underground utilities, and debris within the planned development area.
   • Over-excavate an additional 1 foot of subgrade to reach approximately 1 foot below the proposed footing elevation.
4. Subgrade Evaluation & Proof-Rolling:
   • Once the initial clearing and excavation are complete, the Geotechnical Engineer should evaluate the exposed subgrade.
   • A fully loaded tandem-axle dump truck (or similar rubber-tired equipment) should be used for systematic proof-rolling to identify unstable soils.
   • If unsuitable soils (soft, loose, organic, or wet) are found, they should be completely removed.
   • The extent of material removal should be confirmed during proof-rolling and excavation.
5. Remediation & Replacement of Unsuitable Materials:
   • Any areas showing excessive deflection during proof-rolling should be undercut as recommended by the Geotechnical Engineer.
   • The undercut areas may be backfilled with select fill, such as:
     • Graded aggregate base
     • No. 57-sized crushed stone
     • Compacted structural fill
   • All undercutting should be observed by the Geotechnical Engineer to confirm proper material removal and to prevent unnecessary excavation.
6. Reinforced Zone Preparation:
   • Once the subgrade is approved, a 12-inch layer of No. 34 stone should be placed within the entire reinforced zone.
   • This stone layer should be sandwiched between woven geotextile fabric (such as Mirafi HP 270 or equivalent).
   • Once this layer is placed, retaining wall construction can proceed as planned in accordance with industry standards.
7. Additional Considerations:
   • Large rock boulders (greater than 2 feet in size) were observed in certain areas, along with mixed debris and organic matter. These should be removed before placing new fill.
   • One soil sample was collected for Proctor testing and has been delivered to the ASEC laboratory for analysis.

We appreciate the opportunity to assist with this project. If you have any questions regarding this report, please feel free to contact us.

Test pit behind lot 227

Test pit behind lot 226

Test pit behind lot 226

Test pit behind lot 226

Test pit behind lot 228

Test pit behind lot 226

Test pit behind lot 229