Once a potential construction site has been selected based on specific client needs and initial issues have been identified, the next step is a thorough site analysis. This site analysis will give project managers a comprehensive review of site feasibility, potential return-on-investment, and stabilization needs.
Within 4 to 6 weeks, the Riley Construction team and civil engineers can complete a diligent analysis of site issues. This analysis will determine whether a building project moves forward or if it’s back to the drawing board.
The key phases of site analysis are as follows:
Phase 1
- Evaluation of the site’s location, topography, soil cut and fill, utility access, and cost of infrastructure.
- Zoning: Is the site zoned for the type of building and use? If not, can it be rezoned to accommodate for its intended purpose?
- Environmental background inspection or contamination reporting verification
- Determine if the site contains any existing structures or infrastructure that would need to be relocated, such as underground power, gas, or fiber optic lines.
- Evaluate general cost parameters.
- Enter a purchase and sale agreement with the land seller.
Phase 2
- Soil condition evaluation, including soil borings and test pits.
- Geotechnical analysis provides information on soil types, bearing capacity, and potential hazards including bedrock or buried obstructions.
- Wetland review and delineation identifies any wetlands or other protected areas that may impact development.
- Environmental analysis determines if there are any potential environmental hazards or contamination on-site.
- Traffic analysis determines potential increases in traffic. Some municipalities require this analysis.
- Development tax incentives or credits from local or state municipalities may be available.
- Review storm water management design and local requirements along with schematic water and sewer utility designs.
- Further design development and cost analysis of mass grading, including understanding how much dirt needs to be moved, imported, or exported.
Phase 3
- Complete a detailed analysis of the site design and engineering, including the layout, grading, drainage, and utility design. This will help determine the feasibility and cost of the project and identify potential challenges.
- Once the issues are identified, determine the stabilization plan and cost to fix.
- Evaluate the cost-to-spend ratio once expenses are determined.
Build on a solid foundation
A variety of poor and unstable soil conditions can add significant cost and time to a construction project. Understanding soil properties is critical to knowing how to achieve structural requirements to build on top of them.
Site stabilization refers to the means and methods required during construction to make soils meet structural bearing capacity required to support new structures. This directly relates to understanding soil properties and how to effectively work with the soils.
Achieving stable site soils is critical for both the short- and long-term use of the site. In the short-term, proper soil management is critical during construction activities and for accelerating schedules to minimize unnecessary cost during construction. This leads to proper construction planning and cost estimates for the owner. Unstable sites also can be unsafe for workers, equipment, and materials. In the long-term, properly prepared subgrade solids provide long-term stability and minimize settling and cracking in interior and exterior slabs, parking lots, and roads. This is a cost-effective investment to avoid premature failures.
How to address poor or unstable soil conditions
Stabilization involves a range of techniques and processes that help stabilize the subgrade soils, drainage systems, and help control moisture content and achieve proper compaction of soils to support structures above.
Each individual construction project will need to be assessed before site stabilization solutions are determined. To start, it is important to understand the type of soil you are dealing with and how to properly manage moisture requirements and workability of those soils.
- A soil boring report is critical for strategic decision-making. For instance, sandy or silty soils vs clay materials can affect how soils are stabilized and remediated, and how moisture can affect the soils. Lime (lime kiln dust or quick lime), a white alkaline substance containing calcium oxide, does not work well in sandy soils, whereas Portland cement is typically required to achieve a chemical reaction with the soil.
- Soil stabilization involves changing the soil’s chemical or physical makeup. There are also various mechanical methods that can be applied, such as discing or drying wet soils (if weather allows). If there are wet soil issues, lime or Portland cement can be added to absorb moisture.
Properly understanding your soils is critical for completing a good cost analysis and risk assessment for your project up front. When not properly analyzed, these items can create major cost and schedule impacts. In addition to soil quality, soil bearing capacity is critical.
- Soils with low bearing capacities or undocumented (existing) fill soils will impact the size of building foundations required and could require wider and deeper foundations.
- Soils must be tested during construction and meet required bearing capacity before anything can be installed, such as foundations, pavement, or concrete slabs.
- An analysis of alternative foundations might be needed. For example, aggregate piers are columns of compacted stone installed in poor soil to increase bearing capacity and mitigate settlement under structural components.
- Alternate designs can be reviewed with the structural engineers to consider thicker stone base sections under slabs and pavements. Thicker pavements and concrete slabs may be considered and compared to the cost of adding chemical stabilization to the soil.
Site due diligence is a critical step that impacts both the short and long-term costs of your project. This site analysis arms project managers with a comprehensive understanding of site feasibility, potential return-on-investment, and stabilization needs. To learn more about how to analyze and stabilize your next building project site, contact Project Development Manager, Alex Egan at alexe@rileycon.com.