Loading...
HomeMy WebLinkAboutObservation of ExcavationCopyright © 2026 GeoStrata 1 Excavation Observation - 5810 CR 320 Modular Home April 30, 2026 Mr. David Mahovsky Clayton Homes of Grand Junction 371 23 Road Grand Junction, Colorado 81505 970-260-8815 GeoStrata Project No. 2088-001 RE: Foundation Excavation Soils Observation for 5810 CR 320 Modular Home Garfield County, Colorado Mr. Mahovsky: As requested and in accordance with our Master Service Agreement dated April 16, 2026 and executed on April 17, 2026, GeoStrata performed an observation of the foundation excavation for the proposed modular home located at 5810 County Road 320 in Garfield County, Colorado on April 22, 2026. A geotechnical report prepared by GeoStrata titled “Geotechnical Engineering Report 5810 County Road 320 Proposed Modular Home, Garfield County, Colorado” and dated November 21, 2025 (GeoStrata Job No. 1869-004) was reviewed as part of our foundation excavation observation. During our foundation excavation observation at the proposed modular home we were looking for compliance with the recommendations contained in the geotechnical report which are summarized as follows: • Any unsuitable soils such as vegetation, topsoil, undocumented fill, debris, and soft, loose, or disturbed soils should be removed prior to the placement of the structural fill material. • As over-excavation was required, the excavation should extend one foot laterally for every one foot of depth required of over-excavation. • Footings should be placed entirely on 3-feet of properly placed and compacted structural fill for a maximum net allowable bearing capacity of 2,000 psf. • Maximum 6-inch loose lifts if compacted by small hand-operated compaction equipment, maximum 8-inch loose lifts if compacted by light-duty rollers, and maximum 12-inch loose lifts if compacted by heavy duty compaction equipment that is capable of efficiently compacting the entire thickness of the lift. We recommend that all structural fill be compacted on a horizontal plane, unless otherwise approved by the geotechnical engineer. Structural fill should be compacted to at least 95% of the maximum dry density, as determined by ASTM D- 1557, based on the imported fill material proposed by the Contractor (per our recommendations) that meets Colorado Department of Transportation Class 2 Aggregate Base Course gradation specifications. Observations At the time of our site visit on April 22, 2026, the foundation excavation had been completed and ranged from approximately 4 to 4 ½ feet in depth below the existing site grade. The soils exposed in the excavation sidewalls and floor comprised of slightly moist, sandy to very sandy clay with gravel lenses and pockets which were consistent with the soils encountered in our test pits excavated during 2487 Industrial Boulevard, Grand Junction, Colorado 81505 T: (801) 501-0583 ~ info@geostrata-llc.com Copyright © 2026 GeoStrata 2 Excavation Observation - 5810 CR 320 Modular Home our previously referenced geotechnical investigation. This material was observed to underlie the entire foundation excavation bottom and to comprise of undisturbed native soil. GeoStrata observed that all unsuitable soils such as vegetation, topsoil, undocumented fill, debris, and soft, loose, or disturbed soils were removed from the excavation bottom. We recommend the footings be placed upon 3-feet of properly placed and compacted structural fill. Based on our observations and the soils encountered during our previously referenced geotechnical engineering report, the exposed soils at the bottom of the excavation are suitable native soils for the placement of 3-feet of properly placed and compacted structural fill beneath the footings for a maximum net allowable bearing capacity of 2,000 psf. Conclusions and Recommendations Based on our observations, the recommendations in the soils report pertaining to foundation excavation, over-excavation, and excavation bottom soil suitability have been complied with and the site is suitable for the placement of 3-feet of properly placed and compacted structural fill beneath the footings for a maximum net allowable bearing capacity of 2,000 psf. Exposed foundation soils should be protected against freezing prior to and during footing and foundation construction. Freezing of foundation soils could result in excessive total and differential settlements causing structural damage. If soils in the foundation excavation are allowed to freeze, the soil s which were frozen should be over- excavated and removed. The over-excavation should be backfilled with properly placed, compacted and tested suitable structural fill. Soils loosened during preparation of the foundation should be re- compacted prior to footing placement. The footings should not be placed on soft or pumping soil, or in areas of ponded water. Perched groundwater elevation can be altered by flood irrigation and/or other surges of water introduced to the subsurface. As an added precaution the following moisture protection mitigation recommendations should be implemented to help reduce the risk of potential settlement from occurring. These items are summarized as follows: • Minimum embedment of the footings for frost protection should be 36-inches below ground surface. • Moisture should not be allowed to infiltrate into the soils in the vicinity of the foundations. As such, design strategies to minimize ponding and infiltration near the structure foundations should be implemented. • The ground surface within 10 feet of the entire perimeter of the building should slope a minimum of 5% away from the structure. Alternatively, a slope of 2% is acceptable if the water is conveyed to a concrete ditch that will convey the water to a point of discharge that is at least 10 feet from the structures. • Roof runoff devices (rain gutters) should be installed to direct all runoff a minimum of 15 feet away from the structure. Rain gutters discharging roof runoff adjacent to or within the near vicinity of the structure may result in excessive differential settlement. • We recommend irrigation around foundations be minimized by selective landscaping and that irrigation valves be constructed at least 15 feet away from foundations. • Jetting (injecting water beneath the surface) to compact backfill against foundation soils may result in excessive settlement beneath the building and is not allowed. Copyright © 2026 GeoStrata 3 Excavation Observation - 5810 CR 320 Modular Home • Backfill against foundations walls should be placed in lifts and compacted to 90% modified proctor to create a moisture barrier. In areas where collapsible soils are present, backfill should consist of fine-grained soils. • Any additional precautions which may become evident during construction. • If undocumented fill or collapsible soils were identified at the site, the Contractor and Owner should be aware that if driveways, sidewalks, or other flatwork is constructed on the undocumented fill or collapsible soils, these improvements have a high potential to settle. All recommendations in the geotechnical report should be complied with during construction of these improvements. Over-wetting of the native or fill soils beneath the footings by natural or man-made means prior to, during or after construction may result in soil stability problems and potential excessive settlement of the soils. Failure to comply with these recommendations could result in excessive total and differential settlements causing structural damage. Limitations The observations for the above referenced building lot are limited to the issues specifically identified in this letter. This letter addresses the soils observed in the foundation excavation for the foundation of the proposed residence (modular home) only. Soils underlying sidewalks, driveways, and other flatwork were not observed and are outside our scope of services. The GeoStrata 2025 geotechnical report should be read in its entirety and all recommendations followed. This letter only contains portions of the GeoStrata 2025 geotechnical recommendations relevant to foundation footings. GeoStrata has relied on the geotechnical engineering report in performing its services. All services were completed in accordance with the current standard of care, no other warranty expressed or implied is provided. No laboratory testing or engineering analysis was performed as a part of this observation. All services were performed for the exclusive use and benefit of the above addressee. No other person is entitled to rely on GeoStrata’s services or use the information contained in this letter without the express written consent of GeoStrata. We did not supervise, direct or have any control over any of the Contractor’s or Subcontractor’s work. We were not responsible for the Contractor’s or Subcontractor’s scheduling of our services, means, methods, procedures, techniques, or sequences of construction, nor responsible for ensuring that any Contractor or Subcontractor performed or completed the work in accordance with the contract documents or construction industry standards.