Planning Your Pool Excavation in Franklin County: Why Site Assessment and Soil Testing Are Your First Steps to Success

When you’re ready to transform your backyard with a swimming pool in Franklin County, Washington, the excitement of envisioning summer gatherings and relaxing afternoons can make it tempting to jump straight into construction. However, smart property owners know that proper planning begins underground. Certainly one of the least conspicuous but most critically important design considerations for an on grade or in-ground commercial swimming pool structure are the geotechnical conditions (soil conditions). Variations in geotechnical conditions can drastically influence the design approach for the pool structure, pool shell construction methods, and in some cases the pool maintenance protocol as well.

Understanding Franklin County’s Unique Soil Conditions

Franklin County’s diverse landscape presents unique challenges for pool excavation projects. The region’s soil composition varies significantly across different areas, from sandy loam near the Columbia River to clay-heavy soils in agricultural zones. Soil properties can vary dramatically in an area, so the design approach used on an adjacent site may not be appropriate for your pool. This variability makes professional site assessment not just recommended, but essential for every pool project.

Soil properties can dictate the difference between a simple slab-on-grade design and a more elaborate structural solution requiring deep foundations, over-excavation, soil conditioning, subsurface drainage, piping encasement, or some combination of the like. Understanding these conditions early in your planning process can save thousands of dollars and prevent construction delays.

Washington State Building Code Requirements

Pool excavation in Franklin County must comply with Washington State Building Code requirements, which establish specific standards for soil and foundation work. Geotechnical investigations shall be conducted in accordance with Section 1803.2 and reported in accordance with Section 1803.6. Where required by the building official or where geotechnical investigations involve in-situ testing, laboratory testing or engineering calculations, such investigations shall be conducted by a registered design professional.

The building code also addresses pool-specific concerns, particularly regarding slope stability. That portion of the pool wall within a horizontal distance of 7 feet (2134 mm) from the top of the slope shall be capable of supporting the water in the pool without soil support. This requirement underscores the importance of proper site assessment before excavation begins.

Essential Site Assessment Components

A comprehensive site assessment for pool excavation should address several critical factors:

• Soil Classification: Soil materials shall be classified in accordance with ASTM D2487. This standardized classification helps determine bearing capacity and construction requirements.
• Groundwater Evaluation: If groundwater is present at excavation depth, dewatering methods will be necessary to facilitate construction. Once the pool is in place, groundwater higher than the lowest point of an inground pool structure will exert buoyant forces on the shell. If the structure has not been designed to counteract such forces, an empty pool shell may literally float out of the ground, causing significant damage or catastrophic failure.
• Slope Stability Analysis: Essential for properties with any grade variation
• Drainage Patterns: Both surface and subsurface water movement

Professional Soil Testing Requirements

Proper soil testing involves more than just digging a hole and looking at the dirt. For swimming pool design, it is typically recommended that one boring be taken for each 5,000 SF of pool area, and if multiple pools are included in the project, the borings be located accordingly with at least one taken for each pool. Required boring depth is determined by the geotechnical engineer based on soil conditions, but in any case should not be less than 5 feet below the greatest excavation depth of the swimming pool.

Data collected from boring samples will be used to determine subgrade soil properties, including but not limited to soil gradation, density, bearing capacity, shrink and swell potential, plasticity, lateral earth pressures, and groundwater conditions. This comprehensive analysis provides the foundation for safe, effective pool construction.

Common Soil-Related Challenges in Pool Construction

Franklin County properties may encounter several soil-related challenges during pool excavation:

Expansive Soils: Some common design solutions in dealing with expansive soils are over-excavation of the site to replace expansive material with more suitable soil, and/or structurally supporting the pool shell with deep foundations. When over-excavation is necessary, the geotechnical engineer will recommend the depth to which high plasticity or expansive soils must be removed from the site to limit swell potential.

Groundwater Issues: In some cases, a subsurface drainage system is needed to remove groundwater surrounding the shell. The subgrade preparation for the pool slab and, in some cases, the backfill material must be designed to allow drainage when build-up of hydrostatic pressure is a possibility.

Regulatory Compliance and Permits

Pool excavation projects in Franklin County may require various permits depending on project scope. Construction site operators are required to be covered if both of these apply: Your construction project disturbs land* through clearing, grading, excavating, or stockpiling of fill material. Sites that disturb one acre or more typically require stormwater permits.

Erosion control measures must be in place prior to any clearing, grading, or construction. These control measures must be effective to prevent stormwater runoff from carrying soil and other pollutants into surface water or stormdrains that lead to waters of the state.

Working with Professional Excavation Contractors

Successful pool excavation requires experienced professionals who understand local conditions and regulations. When selecting an excavation contractor Franklin County, WA, look for companies with demonstrated expertise in site assessment and soil management.

Nailed It Construction TC exemplifies the kind of professional approach needed for successful pool excavation projects. At Nailed It Construction, we believe quality craftsmanship and honest service are the foundation of every great project. We proudly serve the entire Franklin & Benton County, WA, bringing years of experience, precision, and creativity to every build. From site prep to drainage solutions, we provide professional excavation services to ensure a solid foundation for your next project. Precision, efficiency, and reliability guaranteed.

With over 30 years of experience in the industry, we take pride in our reputation for high-quality craftsmanship, attention to detail, and unwavering dedication to our clients. Our team of skilled professionals approach every project with a passion for excellence, ensuring that each build is completed on time and within budget with superior workmanship.

Cost Considerations and Planning

While thorough site assessment and soil testing require upfront investment, they prevent costly surprises during construction. Depending on the number of samples, an average residential property should cost $90–$300 (prices checked in 2025). This modest cost for soil testing can prevent thousands in construction delays and redesign expenses.

Based in Kennewick, WA, we understand the unique needs of Tri-Cities properties, from navigating local building codes to choosing materials suited for Eastern Washington’s climate. This local knowledge proves invaluable in planning excavation projects that account for regional soil conditions and weather patterns.

Next Steps for Your Pool Project

Before breaking ground on your Franklin County pool project, prioritize comprehensive site assessment and soil testing. Remember, it is critical to consult a qualified geotechnical engineer for any site. This professional evaluation, combined with experienced excavation contractors, sets the foundation for a successful pool installation that will provide years of enjoyment.

Proper planning today prevents problems tomorrow. By investing in thorough site assessment and working with qualified professionals who understand Franklin County’s unique conditions, you’re ensuring your pool project proceeds smoothly from excavation through final installation.