Geotechnical Engineering Report Addendum No 1 Results of Testing 01 29 2025 submission

Mavis #2296 Additional Exploration January 29, 2025 ECS Project No. 44-2100-A Page 3 GROUNDWATER During the test pit exploration, groundwater was not observed within the test pits. No water was observed entering the other test pits; however, each of the test pits were not left open for 24-hour to monitor the seasonal high-water determination (SHWT). No mottling was observed in any of the test pits as well. The possibility of groundwater level fluctuations should be considered in stormwater design development. Variations in perched groundwater levels and long-term water table may occur as a result of changes in precipitation, evaporation, surface water runoff, construction activities, and other factors. INFILTRATION TEST RESULTS As previously indicated, field infiltration testing was performed within two of the test pits in general accordance with the Appendix to Chapter 12 of the BMP Manual, Subsection A5, Single Ring Infiltration Test. Findings from our field infiltration testing are reported on the Single Ring Infiltrometer Test Logs contained in the attachments. Listed in the following table present the hydraulic conductivity rate of the soil layers tested as determined by the procedure outlined in Subsection A5. TESTED SOIL APPROXIMATE USDA TEXTURAL HYDRAULIC TEST PIT INFILTRATION TEST CLASSIFICATION AT CONDUCTIVITY RATE DESIGNATION TEST ID ELEVATION TEST ELEVATION (inch/hour) TP-01 TP-01A ±615.0 SANDY LOAM 0.04 TP-02 TP-02A ±615.0 SANDY LOAM 0.39 EXISTING FILL AND SHALLOW FOUNDATIONS Based on the visual observation of the fill materials encountered while test pitting the existing fill materials on the site do not appear to be suitable for support of the building foundations. The existing

n the visual observation of the fill materials encountered while test pitting the existing fill materials on the site do not appear to be suitable for support of the building foundations. The existing fills are variable in composition, containing deleterious debris such as brick, plastic, glass, and metals. Therefore, the recommendation included in the report should be followed and these materials should be removed in their entirety below foundation elements and heavily proofrolled during site grading operations in areas supporting pavements and slabs on grade. CLOSING This letter has been prepared as an addendum to our Geotechnical Engineering Report dated December 10, 2024 (under ECS Project No. 44:2100); as such, it should only be utilized in conjunction with that exploration and report. Should any of the assumptions outlined above regarding the proposed conditions be inaccurate, alternative recommendations may apply including those provided in our geotechnical report.