A pool is a structure, and the ground beneath it decides more about that structure than the drawing does. Here is how a geotechnical investigation works, what its numbers mean and why it shapes both the pool and the price — written with an engineer's precision, translated as we go, and finished with a complete caisson design, sheet by sheet.
Santa Barbara Pools Design and Build · CSLB 1129965 · Reviewed September 2026
Unless a yard is flat or very nearly so, most pools here call for a soils or geotechnical report. A geotechnical engineer drills borings on the property, has the samples tested in a laboratory, and reports how the ground will carry the load, how it will swell, shrink and settle, and how any slope beside it will behave. The structural engineer designs the shell to those findings. That is why the report comes first, and why on many properties a proper quote follows it rather than precedes it.
When a pool needs one
Unless the yard is flat or the slope is very minor, plan on a report. These are the triggers we see most often:
The pool sits within approximately ten feet of a slope.
The water is deeper than approximately six feet.
The property carries significant elevation change.
There is known poor or uncertified fill on site.
The jurisdiction, the coastal zone or a hillside overlay requires one regardless.
Behind those triggers sits the building code. The California Building Code requires a geotechnical investigation for foundation design unless the building official is satisfied that adequate data already exists (§1803). It classifies soil with an expansion index above 20, measured under ASTM D4829, as expansive, with design consequences that follow (§1803.5.3). And it sets a pool back from a slope by half the setback a building footing would need, adding that any portion of the pool wall within seven feet of the top of the slope must be capable of holding its water with no support from the soil at all (§1808.7.3).
Individual agencies add their own layer. Los Angeles asks for a soils report wherever expansive soil or uncertified fill is present. Malibu requires a soils memo listing every geology, geotechnical and coastal engineering report on the property. Ventura takes soils and geotechnical reports in with the plan set. We tell you which apply to your address at the site walk, before anything is priced.
In plain terms. The triggers are simply the questions a careful engineer asks before putting a stamp on a drawing. Is there a hill nearby? How deep is the water? How much does the ground rise and fall? Has anyone ever brought in dirt of unknown quality? If the answer to any of them is yes, you want facts rather than assumptions.
Why the ground here is unusually complicated
The South Coast is young, folded and still moving, and its ground changes accordingly. Along the foot of the Santa Ynez Mountains runs the Rincon Formation, a clay-rich shale that the USGS describes as susceptible to landsliding, and that weathers into dark soil with significant shrink-swell potential. Montecito is built on alluvial fans, cones of sediment and boulders carried down from the range by debris flows over thousands of years. Hope Ranch and much of the coastline sit on uplifted marine terraces over shale bedrock. The flats hold young, loosely consolidated alluvium and, near the water, shallow groundwater. Add a century of hillside grading and undocumented fill, and two lots on the same street can ask for entirely different structures.
In plain terms. Building here is a little like building on a layer cake that changes flavors every few houses: sponge-like clay on one lot, a buried boulder field on the next, loose fill on a third. From the surface, they can all look like the same lawn. The only way to know which slice you have is to take a sample.
And all of it is seismic. For structures in Seismic Design Categories C through F, the code has the investigation evaluate slope instability, liquefaction, total and differential settlement, and surface displacement from faulting or seismically induced lateral spreading (§1803.5.11). In categories D through F, where coastal Santa Barbara sits, it adds dynamic seismic earth pressure on walls retaining more than six feet of backfill, liquefaction potential at the site's peak ground acceleration, and the consequences and mitigation of any strength loss (§1803.5.12).
In plain terms. Shake a jar of wet sand and the water rises to the top while the sand loses its grip. In a strong earthquake, some saturated sandy ground does much the same thing. Part of the engineer's job is to tell you whether yours is that kind of ground, and if it is, what the foundation does about it.
How the investigation works
It begins on the property. The geotechnical engineer drills exploratory borings at the pool footprint and the structures around it, typically with a truck- or track-mounted hollow-stem auger, or with limited-access equipment on tight hillside sites. At set depths, a driven sampler recovers relatively undisturbed cores, and the number of hammer blows needed to advance it is recorded, a direct field measure of the soil's density and strength. In the Standard Penetration Test, a 140-pound hammer falls 30 inches and the blows counted over the last foot of an eighteen-inch drive become the N-value: in sand, fewer than about 10 reads as loose and more than 50 as very dense. Each stratum is logged, groundwater is noted, and the samples go back to the laboratory.
There they are tested under controlled conditions, and each test answers a specific design question:
Test
Standard
What it tells the engineer
In plain terms
Moisture and in-place density
ASTM D2216, D2937
The soil's water content and dry density as it sits today, the baseline for every other result.
How full the sponge is, and how firmly it is packed.
Classification
ASTM D6913, D4318, D2487
Grain-size distribution, plasticity limits and the Unified Soil Classification group, such as CL or SM.
Sand, silt or clay, and how sticky it gets when wet.
Maximum density
ASTM D1557
The laboratory benchmark that compacted fill is later tested against in the field.
The definition of fully packed.
Expansion index
ASTM D4829
Volume change of a compacted specimen soaked under a standard surcharge.
How much it swells when it gets wet.
Direct shear
ASTM D3080
Friction angle and cohesion, the inputs to bearing, earth pressure and slope stability.
How hard it resists sliding.
Consolidation and collapse
ASTM D2435, D4546
Compression under sustained load, and any sudden collapse when the specimen is inundated.
How much it squashes, and whether water makes it slump.
Corrosivity
Caltrans CTM 417, 422, 643
Soluble sulfate, chloride, pH and minimum resistivity, which set cement type, water-to-cement ratio and cover over the steel.
Whether the soil will quietly attack the concrete and the rebar.
The report that follows turns those numbers into design values and recommendations the structural engineer can build on.
In plain terms. Think of it as a biopsy for the backyard. A narrow core comes out of the ground, a few inches wide and many feet deep, and the laboratory reads it the way a physician reads a sample: what it is made of, how strong it is, how it behaves when it gets wet, and whether it will quietly attack the concrete that sits on it.
What the numbers mean
Bearing capacity
The pressure, in pounds per square foot, that the soil can carry without shearing or settling excessively. Where the building official allows it without an investigation, the code's presumptive values run from 1,500 psf for clays and silts to 2,000 for sands, 3,000 for gravels, 4,000 for sedimentary rock and 12,000 for crystalline bedrock; undocumented fill is given no presumptive value at all (Table 1806.2).
Counterintuitively, gross bearing capacity is rarely what governs a pool. An average residential pool holds on the order of 20,000 gallons, more than 80 tons of water, yet it usually weighs less than the soil dug out to make room for it: a cubic foot of soil weighs roughly 110 to 130 pounds, a cubic foot of water 62.4. What governs is how evenly the ground carries the load that remains, and where it is concentrated: under the bond beam, beneath raised walls and at the tips of caissons.
In plain terms. Snowshoes and stilettos. The same person sinks into fresh snow or glides over it depending on how their weight is spread and what they are standing on. And a pool is a little like swapping a filing cabinet for an aquarium of the same size: the floor is often carrying less than before. The risk is not the weight. It is the floor shifting unevenly underneath.
Expansion
Expansive clays take water into their mineral structure and swell, then shrink as they dry. The expansion index quantifies it, and ASTM D4829 grades the result as very low (0 to 20), low (21 to 50), medium (51 to 90), high (91 to 130) or very high (above 130). Above 20, the code treats the soil as expansive, and at the higher classifications the uplift is enough to heave and crack slabs and shells that were never designed for it. Structural plans on clay sites commonly require the excavation to be moistened before concrete is placed, so the clay has taken on water before the shell is built against it.
In plain terms. A sponge that swells after the winter rains and shrinks in August. Under a pool, that seasonal breathing pushes unevenly on the shell, year after year.
Settlement and collapse
Consolidation testing predicts how much the ground will compress under a sustained load. Some dry, low-density soils do the opposite of swelling: they collapse when first wetted, a condition called hydroconsolidation, which a pool's own water can trigger.
In plain terms. Most ground behaves like a new mattress that settles a little and then holds. Collapsible soil behaves more like a sandcastle: firm while it is dry, slumping the moment the water reaches it.
Shear strength and slopes
Direct shear results give the friction angle and cohesion that engineers use to model slope stability, the lateral earth pressure on the pool walls, and the creep zone near a descending slope, the outer skin of soil that moves downhill slowly over years, within which footings must be taken deeper to reach ground that is not moving.
In plain terms. On a slope, the top few feet of soil can drift downhill so slowly you would never see it, like a glacier measured in decades. The answer is to reach beneath that moving layer to ground that is staying put.
Groundwater
Shallow groundwater imposes hydrostatic uplift on a shell that is emptied or partly drained. The design may call for hydrostatic relief, subdrains, or added mass to resist it.
In plain terms. An empty boat floats. An empty pool in saturated ground wants to do the same, which is why a pool should never be drained without the right relief in place.
Corrosivity
Soluble sulfates and chlorides in the soil determine the cement type, the water-to-cement ratio and the concrete cover over the reinforcing steel.
In plain terms. Some soils are quietly corrosive. Knowing that before the shell is shot decides the concrete recipe that will outlast it.
What the structural engineer is solving for
With the report in hand, the structural engineer's first concern is movement, and specifically differential settlement rather than total settlement. A pool is a rigid, monolithic shell carrying tens of tons of water, with a waterline that reveals the smallest tilt. If one end settles more than the other, the shell is forced to bend. Engineers express the severity of that bending as angular distortion: the difference in settlement between two points, divided by the horizontal distance between them.
Geotechnical reports typically state an estimated total settlement and an allowable differential over a stated horizontal distance. A report might, for example, allow half an inch of differential over forty feet, an angular distortion of about 1/960. For scale, Bjerrum's classic 1963 criteria put the safe limit for buildings where cracking is not permissible at 1/500, which across a forty-foot pool is less than one inch from end to end.
The structure is then proportioned so the shell tolerates that movement without cracking, while its walls resist two opposite loads that never act together: the outward pressure of the water, about 440 pounds per square foot at the floor of a seven-foot deep end, and the inward pressure of the soil when the pool stands empty, which the report expresses as an equivalent fluid weight in pounds per cubic foot.
In plain terms. Picture a dining table with one leg a little short. Total settlement is the whole table sinking evenly into a thick rug, and nobody notices. Differential settlement is the short leg. Angular distortion is how far the tabletop tilts across its length. Water is the most honest level there is: if a pool tilts, the tile line tells everyone.
A section through a hillside pool
Illustrative section, not to scale.
Boring and samples. Cores recovered at set depths and tested in the laboratory.
Undocumented fill. Soil placed without engineering control, and the least predictable layer on many lots.
Expansive clay. Swells when wet and shrinks when dry, pushing unevenly on anything built over it.
Competent material. The ground the structure is ultimately taken down to.
Caissons and grade beam. Piers drilled through the fill and clay into competent material under the full perimeter of the shell, tied together by a grade beam, so no part of the pool rests on the soil and it cannot settle unevenly.
Creep zone. The slowly moving outer skin of the slope, which footings are taken beneath.
Seven feet from the top of slope. Within this distance the pool wall must hold its water without help from the soil.
The structural answers
Each finding in the report has an engineering response, and most sites use more than one:
A heavier shell. Thicker sections, larger bars at closer spacing, and a deeper or thickened bond beam where a slope or poor ground demands it.
Over-excavation and recompaction. Unsuitable soil is removed below and beyond the shell, moisture-conditioned and replaced in thin, compacted lifts. The grading appendix of the California Building Code calls for fill compacted to at least 90 percent of maximum density under ASTM D1557, placed in lifts no more than twelve inches thick.
Deepened footings. Taken below the creep zone and outside the setback that the code requires from the face of a slope.
Drilled caissons and a grade beam. Cast-in-place concrete piers drilled down into competent material around the full perimeter of the shell and tied together by a grade beam, so the whole pool bears on a structural frame rather than on questionable soil. Carrying only one side would leave the rest on soil, and two foundations that settle differently are the very thing the design exists to prevent.
Drainage and relief. Subdrains, hydrostatic relief and moisture control, so water never builds up behind a wall or beneath the floor.
In plain terms. Over-excavation is replacing a sagging mattress with a firm, properly built one before anyone lies on it. Caissons are the pilings under a pier: the sand at the surface may shift, but the pier stands on legs that reach something solid. And every leg of the table gets one. Put pilings under only one end and you have built the short leg on purpose.
How caissons are designed
A caisson design starts with four numbers from the soils report: how much load the soil can take along the side of a pile (allowable skin friction), how much it can take at the tip (allowable end bearing), how hard the soil pushes on a wall (active earth pressure), and how hard it pushes back when a foundation is shoved into it (passive resistance). The structural engineer works out the load that reaches each pile, then sets its diameter, how far it goes into firm native soil, and its steel, pile by pile. The piles run the full perimeter of the shell, corners and mid-walls alike, so every wall bears on the same foundation and the pool cannot settle more at one end than the other.
In the field, each hole is drilled through the fill into firm native soil and its bottom is cleaned of loose cuttings with a flat cleanout auger, so the concrete bears on undisturbed ground. The geotechnical engineer looks at the hole and its steel before concrete goes in, a special inspector keeps a record of every pile, and the concrete is placed soon after drilling. The top of each pile is left a few inches high so it keys into the grade beam or floor above, which makes that construction joint easier to clean and stronger once it is poured.
The deck needs a decision as well. A pool on caissons and a deck on soil will not move together, so the deck is either built to flex, with pavers and open or planted joints, or carried on the pool walls and the same foundation.
Below, the plan for a recent Santa Barbara pool and spa on ten caissons is read line by line. The full drawing set follows the article.
A pile carries load two ways: friction along its sides, the way wood grips a nail, and bearing at its tip, like a post standing on a flat stone. A 24-inch pile ten feet into firm soil works out to about 62,800 pounds of friction and 9,400 of end bearing: roughly 36 tons of design capacity from one pile.
24" DIA. CAISSON EMBED 20' MIN. INTO FIRM, UNDISTURBED NATIVE SOIL (SOILS ENGR. TO VERIFY)
Only firm, undisturbed native soil counts. The twenty feet start once the drill is through any fill, and the soils engineer confirms it at the hole, so two piles under the same pool can end at very different depths.
NOTE THAT MID-WALL PILE REINFORCEMENT IS DIFFERENT FROM CORNER PILE REINFORCEMENT.
Ten piles, four different designs. The deepest go twice as far into firm soil as the shallowest and carry three times the vertical steel of the pool corners. Each is sized to its own position and load.
EMBED TOP OF CAISSON 3" INTO POOL WALL/FLOOR (TYP.)
The weakest point in the chain is where two pours of concrete meet. Seating the pile three inches into the shell, like a dowel set in a socket instead of two ends butted together, locks that joint.
#4 SPIRAL TIES @ 3" PITCH TYP. FROM TOP OF CAISSON TO 10' INTO COMPETENT MATERIAL #4 SPIRAL TIES @ 9" PITCH FROM 10' INTO COMPETENT MATERIAL TO BOTTOM
Bending and shear from sideways loads, from the soil or an earthquake, are greatest in the upper part of a pile, so that is where the spiral wraps tightest and confines the concrete. Lower down it opens to nine inches. Think of taping a bat handle: the wrap is tightest where the hands grip.
ACTIVE EARTH PRESSURE: 100 PCF PASSIVE RESISTANCE: 350 PCF
Engineers model soil as a heavy fluid. At 100 pounds per cubic foot it presses on the base of a seven-foot wall at about 700 psf when the pool is empty, against about 440 from the water when it is full. Passive resistance is the ground pushing back on the piles when they are shoved sideways.
#5 @ 6" O.C. VERT, DBL. CURTAIN, STAGGERED, IN BOTTOM OF WALLS TALLER THAN 4'-4"
Pressure grows with depth, so the lower part of a deep wall gets heavier bars at closer spacing. It is the same reason a dam is thickest at its base.
No surcharges are allowed for construction per this plan.
The wall is designed for the loads on the drawing. A new footing too close, a steep bank above the pool or a parked truck adds load it was never designed to carry, so the plan rules them out.
Observe drilling operations for caissons and maintain complete and accurate records for each element. (Continuous)
An independent special inspector watches every hole being drilled and records each one: its location, plumbness, diameter, length and the ground at its tip.
In plain terms. A caisson is a buried stilt, and the plan is the recipe for each stilt: how wide, how deep, how much steel, and who has to see the hole before the concrete goes in. Each number traces back to a line in the soils report, which is why the report comes first.
Three things move the number. The structural design usually gets heavier: a thicker shell, more steel, deeper footings. Over-excavation and recompaction may be added, which is real excavation, real export and real time. And on a slope or over poor fill, the shell may have to sit on drilled caissons and a grade beam rather than on soil. Any one of those changes the figure materially.
This is the honest reason a pool quoted from a photograph is not really a quote for your pool. On a site with any of the triggers above, we would rather give you a range, commission the report, and then give you a number we will stand behind. The report is ordered at the start, in the same window as plan creation and engineering, so it runs alongside the design rather than after it, and it goes into the permit set when we submit.
In plain terms. A quote before the soils report is like a surgeon's estimate before the X-ray. We can tell you the likely range. The report tells us which end of it you are on.
The vocabulary, translated
Allowable bearing pressure
The load per square foot the engineer permits on the soil, with a factor of safety already applied. The weight limit posted on the ground.
Angular distortion
Differential settlement between two points divided by the distance between them, written as a ratio such as 1/500. How far the tabletop tilts.
Caisson, or drilled pier
A cast-in-place concrete pile drilled to competent material, carrying load by skin friction and end bearing. A buried stilt.
Creep zone
The outer mantle of a slope that moves downhill slowly over years; foundations are taken beneath it. The part of the hill that is quietly walking.
Differential settlement
Unequal vertical movement between parts of a structure. The short table leg.
Equivalent fluid pressure
Lateral earth pressure expressed as the weight of a fluid, in pounds per cubic foot, that would push the same way. Soil treated as very heavy water.
Expansion index
The ASTM D4829 measure of how much a compacted soil swells when soaked; above 20, the code treats it as expansive. The sponge score.
Grade beam
A reinforced concrete beam spanning between piles and carrying the structure above. The bridge between the stilts.
Hydroconsolidation
Collapse of a dry, low-density soil on first wetting. The sandcastle at high tide.
N-value
Blows of a 140-pound hammer to drive the sampler the last foot of an eighteen-inch interval. How hard the ground fights back.
Over-excavation and recompaction
Removing unsuitable soil and replacing it in thin lifts compacted to a tested percentage of maximum density. Rebuilding the mattress properly.
Passive resistance
The resistance soil provides when a foundation is pushed into it. The ground pushing back.
Skin friction
Load a pile transfers to the surrounding soil along its sides. How wood grips a nail.
Surcharge
Any added load near a wall, such as a footing, a slope or a vehicle, that increases the pressure it must resist. Extra weight leaning on the wall.
Undocumented fill
Soil placed without engineering observation or testing; the code gives it no presumptive bearing value. Dirt with no paperwork.
What we handle
We identify whether your property needs a report, commission it from a licensed geotechnical engineer, carry its findings into the structural design, and submit it as part of the permit package. If plan check raises a question that traces back to the soil, we answer it. You are never the one coordinating between two engineers and a plan checker.
Requirements change and every parcel is different. Verify with the jurisdiction before relying on any figure here; we do, on every job.
Engineered example
A pool and spa founded on caissons, sheet by sheet.
This is the complete structural plan for a recent Santa Barbara pool and spa carried on drilled caissons, reproduced word for word. Names, the address, the permit number and the title block have been removed. It is here to show how caissons are designed, not as a construction document: every pool is engineered to its own site and its own soils report.
Fine and coarse aggregates shall conform to ASTM c 33 for normal weight concrete.
Combined grading of aggregates shall conform to the requirements of the project specifications.
The concrete shall be mixed and delivered in accordance with ASTM c 94 or ASTM c 685. All concrete work shall be in accordance with ACI 318 and 347.
Concrete for caissons shall be an approved mix with 4” maximum slump and shall attain 4000 psi min. compressive strength at 28 days. Special inspection required. (Note that higher slump may be allowed if achieved using plasticizing agent(s). Submit mix design to engineer for approval.)
During the progress of the work, test cylinders shall be taken. Three (3) shall be taken for concrete used for the caissons; and three (3) from the concrete used for the pool structure, one cylinder from each group shall be tested at 7 days, the second cylinder from each group shall be tested at 28 days. The third cylinder from each group shall be held pending the results of the other tests. All cylinders shall be taken, prepared and tested by an approved testing laboratory.
Before placement of concrete, the contractor shall verify proper placement of all items of work that are embedded in concrete. Caissons shall have been inspected and approved by a soils engineer.
Boreholes & footing excavations shall be free of standing water.
Shotcrete:
All work shall comply with ACI 506.2, “Specification for Shotcrete”.
Shotcrete shall have a min. compressive strength of 3000psi.
All shotcrete construction shall be wet mix only.
During the progress of the work, test cylinders shall be taken. Three (3) shall be taken for concrete used for the caissons; and three (3) from the concrete used for the pool structure, one cylinder from each group shall be tested at 7 days, the second cylinder from each group shall be tested at 28 days. The third cylinder from each group shall be held pending the results of the other tests. All cylinders shall be taken, prepared and tested by an approved testing laboratory.
Reinforcing steel:
All reinforcing steel shall be new and unused deformed bars conforming to ASTM a615. Generally, #4 bars or smaller shall be grade 40 and #5 bars or larger shall be grade 60.
Reinforcement shall be spliced per the table below. All splices shall be located as detailed on plans. Splices of adjacent bars shall be staggered wherever possible. Mesh reinforcing shall be lapped one full square or 6 inches minimum.
Bar size
Min. lap splice
#3
24”
#4
24”
#5
36”
#6
36”
#7
48”
#8
60”
Pool notes:
All construction per this plan shall comply with CBC/CRC 2022, ASCE 7-16 ACI 318-19, and all other applicable current building codes and ordinances.
Contractor shall notify engineer of any apparent discrepancies in this plan prior to proceeding with construction.
It is recommended that a soils investigation be performed by a licensed geotechnical engineer and provided to this engineer prior to construction per this plan. [Engineer of record] assumes no liability for site conditions discovered prior to or during excavation. Additional engineering, at additional cost, may be required depending on site conditions.
If expansive (clay) soils are present, the sides and bottom of excavation shall be moistened prior to placement of concrete. If expansive soils are present in the bottom of excavation, notify engineer prior to placement of reinforcement.
Concrete is to be placed in contact with firm, undisturbed native soil, or certified compacted fill.
All pneumatically placed concrete shall be shotcrete, proportioned and placed per CBC section 1908 and ACI 506.2, with a 28 day compressive strength of 3000 psi. Continuous inspection by a registered deputy inspector is required during placement of all concrete.
Steel reinforcement bars #4 and smaller shall be grade 40 complying with ASTM A615 standards. Reinforcement bars #5 and larger shall be grade 60.
All lap splices in reinforcement shall be 40 bar diameters or 24” minimum. Splices in adjacent bars shall be staggered.
All bond beam reinforcement shall be continuous, and shall wrap around all corners of pool and/or spa. Bend bars behind and under skimmer boxes.
Dimensions noted on plans as “clear” (“clr.”) are to be taken as exact, not minimum.
Unless otherwise noted, all reinforcement is to be placed 3” clear of grade.
Double curtains of reinforcement shall be staggered.
Notify engineer in the event that sufficient groundwater is encountered to cause ponding in the excavated pool bottom.
No surcharges are allowed for construction per this plan. Potential surcharges include: footings adjacent to pool wall, if a line drawn at 1:1 extending downward from the bottom of the footing toe towards the pool wall intersects the pool at any point; ascending slopes greater than 5:1 adjacent to the pool; vehicular travel or parking within a distance from the pool equal to the height of the pool wall in that area.
All electrical equipment shall be properly grounded per CEC article 680.
The concrete for the piles is placed shortly after the pile excavation is drilled, requiring a cold joint between the bottom of a slab or grade beam and the top of the pile. The cold joint connection between the top of the pile and the horizontal structural member that connects to the top of the pile must be flawless. There can be no dirt or other debris on top of the concrete pile when the concrete or the shotcrete for the structural slab or grade beam is placed, and when placed, the concrete must be properly consolidated and/or the shotcrete placed in such a manner as to ensure a properly placed cold joint with no air voids. In order to ensure this happens, the builder should be notified of the importance of this connection by way of a specification on the approved plan. It is further recommended the top of the concrete pile be placed with a top elevation that is 3 inches higher than the bottom of the structural slab or grade beam that connects to the top of the pile so that the top of the pile inserts into the bottom of that structural member. When the top of the pile is built that high, it will make it easier to clean the top of the pile prior to concrete or shotcrete placed in the cold joint.
Structural observations and inspections:
Observations:
Geotechnical Engineer shall be notified 48 hours prior to:
Completion of caisson excavations. Observation to include caisson reinforcement.
Completion of excavation for pool and/or spa.
[Engineer of record] shall be notified 48 hours prior to:
Completion of grade beam reinforcement, prior to placement of concrete.
n/aEngineer’s signature indicates approval to place shotcretedate
Completion of swimming pool and/or spa reinforcement, prior to placement of shotcrete.
Engineer’s signature indicates approval to place shotcretedate
Special Inspection:
Special Inspection is required for:
Caisson Excavation (per CBC 2022 table 1705.8):
Observe drilling operations for caissons and maintain complete and accurate records for each element. (Continuous)
Verify placement locations and plumbness, confirm element diameters, lengths, emebedment into competent material, and end-bearing strata capacity. Record concrete volumes. (Continuous)
Placement of concrete for caissons and grade beams (per CBC 2022 table 1705.3):
Inspection of reinforcing steel and placement. (Periodic)
At the time fresh concrete is sampled to fabricate specimens for strength tests, perform slump and air content tests, and determine the temperature of the concrete. (Continuous)
Inspection of concrete placement for proper application techniques. (Continuous)
Placement of shotcrete walls and pool/spa shell (per CBC 2022 table 1705.3):
Inspection of reinforcing steel and placement. (Periodic)
At the time fresh concrete is sampled to fabricate specimens for strength tests, perform slump and air content tests, and determine the temperature of the concrete. (Continuous)
Inspection of shotcrete placement for proper application techniques. (Continuous)
NOTES
PS-2Swimming pool planSheet 2 of 3SWIMMING POOL PLANSCALE: 1/2" = 1'- 0"Open full size
Pile schedule
Symbol
Pile #s
Diameter
Vert. reinforcement
Min. embedment
1 & 2
18”
(6)-#5
10’ MIN. INTO FIRM, UNDISTURBED NATIVE SOIL
3, 6, 7, & 10
24”
(6)-#6
10’ MIN. INTO FIRM, UNDISTURBED NATIVE SOIL
4 & 5
24”
(10)-#8
20’ MIN. INTO FIRM, UNDISTURBED NATIVE SOIL
8 & 9
24”
(10)-#8
15’ MIN. INTO FIRM, UNDISTURBED NATIVE SOIL
PS-3Structural sectionsSheet 3 of 3SECTION A-ASCALE: 1/2" = 1'-0"Open full sizeSECTION B-BSCALE: 1/2" = 1'-0"Open full size
1) ALL DOUBLE CURTAIN REINFORCEMENT SHALL BE STAGGERED
2) ALL REINFORCEMENT TO BE TAKEN AS 3" CLR. UNLESS OTHERWISE NOTED.
3) IN POOL FLOOR, PLACE TRANSVERSE REINFORCEMENT 3" CLR. OF GRADE AND 2" CLR. OF TOP OF POOL FLOOR, WITH LONGITUDINAL #4 BARS BETWEEN THOSE CURTAINS, AS SHOWN ON SECTIONS, SHEET PS-3.
STRUCTURAL SECTIONS
Drawings redrawn for the web from the approved sheets; dimensions, callouts and notes are as issued. Displayed sizes are not to scale.
Answers
Questions we are asked
Do I always need a soils report?
No. A flat, accessible lot with no history of fill and a conventional depth often does not. In this area, though, more sites need one than do not, and the triggers above are what decide it.
Is a soils report the same as a survey?
No. A survey maps the surface: property lines, elevations and where things sit. A geotechnical report investigates what is underneath: what the ground is made of and how it will behave under the pool. A hillside project usually needs both.
Can you quote my pool without one?
We can give you a range, and we will. A firm number on a site with any of those triggers waits for the report, because the report decides the structure, and the structure is a real part of the price.
What does a soils report cost?
It varies with the property and the scope of investigation the engineer proposes, so we price it with you rather than putting a figure on a web page. It is a known, planned early step, not a surprise halfway through.
What happens if the report comes back with problems?
It is almost always solvable, and far better to learn at the drawing stage than at the dig. The answers are engineering answers: a heavier shell, over-excavation and recompaction, drilled caissons and a grade beam, moving the pool a few feet, or changing its depth. We walk you through each option and what it costs before anything is decided.
What is a caisson, and why would my pool need one?
A caisson, or drilled pier, is a reinforced concrete pile drilled down through fill and weak soil into firm native ground, set around the full perimeter of the shell and tied together with a grade beam, so the whole pool bears on firm ground and cannot settle unevenly. It is used when the soil near the surface cannot be trusted to carry the pool evenly, most often at the top of a slope or over deep fill. The soils report sets how deep they go and what they may carry; the structural engineer sizes each one.
Does it delay the project?
Not when it is ordered at the start, which is how we run it. It is the late soils report that delays a project, because the structural design and the permit set both wait on it.
