constructionengineeringdesign
Why does a splash pad need a geotechnical investigation?
Quick answer
A geotech investigation drills 2-4 soil borings to characterize bearing capacity, frost depth, expansive soils, groundwater table, and infiltration rate. The report drives slab thickness, drainage design, and foundation specs. Skipping it risks slab cracking, settlement, and drainage failure that costs 10x to fix later.
Splash pads are essentially big reinforced-concrete slabs with embedded plumbing and electrical, so soil conditions matter enormously. A geotechnical investigation drills 2-4 soil borings to 10-15 feet, samples soil layers, runs lab tests for plasticity index, swell potential, and California Bearing Ratio, and observes the groundwater table. The geotech report specifies allowable bearing pressure, recommended slab thickness (typically 5-8 inches), reinforcement schedule, frost depth, sub-base aggregate requirements, and infiltration rate for any retention design. Expansive clay soils common in Texas, Oklahoma, and parts of Colorado need special detailing — moisture barriers, post-tensioned slabs, or deeper sub-base. Groundwater within 4 feet of grade may require under-drains. Cost: $4K-12K. Skipping this step and discovering 10-foot fill or shrink-swell clay during excavation can add $50K-200K in remediation. Always commission the geotech before the design is locked.