Foundation Systems & Geotechnical

The foundation is the single point where every decision made by the architect, the structural engineer, and the geotechnical engineer converges into something that has to be built in the ground. It carries every load the structure will ever impose. It resists every lateral force the earth will ever apply. It manages water that the site will shed for the next hundred years. And once the concrete is placed, it cannot be meaningfully changed.

"What kind of foundation do I need?" is the most common question owners ask at the start of a project. It is also a question that cannot be answered without a geotechnical investigation. The answer depends entirely on what is in the ground beneath the building pad: the type of soil, the depth to bedrock, the presence or absence of groundwater, the slope angle, the fill history, and the seismic site classification. Two houses on the same street in the Hollywood Hills can have completely different foundation requirements and completely different foundation costs based on conditions that are invisible from the surface.

On hillside residential projects in Los Angeles, foundation systems can range from $150,000 to over $1.5 million. That range is not exaggeration for effect. It reflects the actual variation in site conditions across the market we work in, and our LA construction cost guide breaks down how foundation scope fits within overall project budgets. A flat lot in Beverly Hills with good bearing capacity at four feet might require spread footings that cost $80,000. A steep hillside lot in Bel Air with 40 feet of colluvium over fractured bedrock, a perched water table at 20 feet, and pre-1963 fill across the upper pad might require a caisson and grade beam system that costs $900,000 before shoring. Same neighborhood, same zip code, completely different project.

This cost reality makes the geotechnical investigation the most important single expenditure in preconstruction. The $15,000 to $25,000 spent on a thorough investigation and well-written report can prevent $500,000 in surprises during construction. The false economy of minimizing preconstruction geotechnical work - fewer borings, less lab testing, a thinner report - is one of the most expensive mistakes we see on residential projects. The surprises are always more expensive than the investigation that would have identified them.

A geotechnical investigation is a subsurface exploration of a building site performed by a licensed geotechnical engineer, typically accompanied by an engineering geologist on hillside sites. The investigation produces a formal report that serves as the basis for all foundation design. In Los Angeles, LADBS requires the geotechnical report before structural engineering can proceed, and the report must be approved by the Department's Grading Division before building permits are issued. Per LAMC Section 91.7006.2, grading permits and hillside construction require soils engineering and engineering geology reports that include data on the nature, distribution, and strength of existing soils, along with conclusions and recommendations for design and construction.

The cost of a geotechnical investigation on a residential site in LA typically runs $8,000 to $25,000 or more, depending on the number of borings, depth of exploration, lab testing required, and site complexity. A flat lot with straightforward conditions might need two borings to 20 feet and cost $8,000 to $12,000. A steep hillside lot with suspected fill, variable geology, and potential slope stability concerns might need six borings to 60 feet or deeper, extensive lab testing, and a slope stability analysis, bringing the total to $20,000 to $25,000 or more. The report is produced by a licensed geotechnical engineer (GE) and, on hillside sites, typically includes an engineering geology report from a certified engineering geologist (CEG).

The investigation begins with exploratory borings - holes drilled into the earth using a truck- or track-mounted drill rig. Residential sites in LA typically require two to six borings, spaced to provide coverage across the building footprint and any retaining wall alignments. Boring depths vary from 15 feet on flat sites with shallow bedrock to 80 feet or more on hillside sites where the geotechnical engineer needs to characterize deep soil profiles and confirm the depth and quality of bearing material.

During drilling, the crew performs standard penetration testing (SPT) at regular depth intervals, typically every 2.5 or 5 feet. An SPT involves driving a split-spoon sampler into the soil with a 140-pound hammer dropped from 30 inches. The number of blows required to drive the sampler 12 inches (the "N-value") provides a field measurement of soil density and consistency. Samples collected during SPT and from continuous sampling in critical zones are sent to a soils laboratory for classification, moisture content analysis, expansion index testing, direct shear testing, consolidation testing, and other analyses depending on site conditions.

A complete geotechnical report provides the information that every subsequent design decision rests on: allowable bearing capacity (the load the soil can support per square foot), bedrock depth and type, groundwater conditions, soil classification using the Unified Soil Classification System, expansion index (a measure of how much the soil volume changes with moisture content), slope stability analysis with factors of safety for static and seismic conditions, fill history, seismic site classification per ASCE 7, and recommended foundation types. The report also provides design parameters for retaining walls, lateral earth pressures, and drainage recommendations.

What the report does not tell you is equally important. Borings are discrete sampling points, and conditions between borings are interpolated, not confirmed. Groundwater levels observed during drilling represent conditions on that specific day - seasonal variations, perched water from irrigation, and subsurface springs may produce different conditions during construction. Conditions below the boring depth are unknown. The report is the best information available, and we rely on it heavily, but field verification during construction remains essential. When the actual excavation reveals conditions that differ from the report - and on hillside sites, that happens regularly - the geotechnical engineer must observe and provide updated recommendations in real time.

When we receive a geotechnical report, we review it for every data point that affects construction planning, cost estimation, and coordination with the design team. The categories below represent what we systematically extract from every report and how it translates into construction decisions. This is the bridge between the engineer's findings and the contractor's execution plan.

Los Angeles has a fill problem that is unlike any other major city in the country, and it traces back to a specific date. Per LAMC Section 91.7011.6, all manufactured fills placed prior to April 25, 1963 are classified as "old fills" and are considered uncertified under modern grading code requirements. Before that date, there were no compaction testing standards, no soils engineer observation requirements, and no documentation of what was placed or how it was compacted. Fill from that era could contain anything: native soil mixed with construction debris, organic material, loosely dumped earth from hillside grading, or material of completely unknown origin. Its composition is unknown. Its compaction is unknown. Its depth is often unknown until you start digging.

Old fill is common across the hillside neighborhoods of Los Angeles. Post-war development in the 1940s and 1950s involved extensive hillside grading, and much of that material was placed without engineering oversight. The fill can appear sound from the surface. It can pass a visual inspection. But when you load a foundation on it, or when it becomes saturated during a wet winter, its performance is unpredictable.

When uncertified fill is identified during the geotechnical investigation or discovered during construction, the typical response is one of two approaches. The first is removal and recompaction (R&R): excavate the fill entirely, process the material (or import certified replacement material), and place it back in controlled lifts with compaction testing and soils engineer observation at every lift. The second is deep foundations that bypass the fill entirely, transferring the building load through the fill to competent bearing material below.

R&R on a hillside site is a fundamentally different operation than R&R on a flat lot, and the cost reflects that difference. The excavated material has to go somewhere, which means trucks on narrow hillside streets, haul route approvals from LADBS and the Department of Transportation, and restricted hauling hours that typically limit truck traffic to 9:00 AM to 3:00 PM on hillside routes. Certified replacement fill has to come from somewhere. Every lift - typically 6 to 8 inches of loose material compacted to 90 percent or greater relative compaction per ASTM D1557 - requires compaction testing by an approved soils testing agency and observation by the geotechnical engineer. And throughout the process, the surrounding slope needs to remain stable during the open excavation, which may require temporary shoring. Discovery of uncertified fill on a hillside project can add $200,000 to over $1 million in unplanned cost, depending on the volume, the depth, the access constraints, and whether the fill extends beneath an existing structure that must remain.

Groundwater on hillside sites in LA is less predictable than most owners expect. The common assumption is that Southern California is dry, so water in the ground is not a concern. In practice, hillside sites regularly encounter perched water tables, seasonal seeps, natural springs, and subsurface drainage from uphill irrigation. The Santa Monica Mountains, the Hollywood Hills, and the hillside neighborhoods of Bel Air and Pacific Palisades have geology that produces perched water in fractured bedrock, at the interface between alluvium and bedrock, and along clay layers that act as aquitards.

When you hit water during caisson drilling, the operation changes significantly. The drill hole must be cased to prevent collapse of the saturated soil. If the water cannot be adequately controlled, the concrete placement method switches from standard free-fall placement to tremie pipe placement, where concrete is pumped through a pipe that extends to the bottom of the hole and is slowly extracted as the hole fills from the bottom up. The concrete displaces the water rather than mixing with it. This requires a different concrete mix design - typically a higher-slump mix with higher PSI specifications to ensure the concrete achieves full structural capacity despite being placed underwater. The cost premium for wet caisson installation versus dry conditions is typically 15 to 25 percent per caisson, driven by the casing, the tremie equipment, the upgraded mix design, and the slower production rate.

The geotechnical report will note the water level observed in each boring at the time of drilling. But that is a snapshot. If the borings were drilled in August after four dry months, the water table in February after sustained rain may be significantly higher. A thorough geotechnical engineer will note this limitation and may recommend seasonal monitoring. For projects where the foundation will be at or near observed water levels, we budget and plan for wet conditions regardless of what the initial borings show.

When the geotechnical report indicates groundwater at or near foundation level, or when field conditions during excavation reveal water that the borings did not predict, the project requires a dewatering system. Dewatering is the active removal of groundwater from the excavation area to create dry, stable conditions for foundation construction. On hillside projects in LA where perched water tables, seasonal seeps, or fractured bedrock aquifers are present, dewatering can be a $50,000 to $200,000 scope item that must be planned before excavation begins.

The most common dewatering method on residential hillside sites is sump pumping: allowing water to seep into the excavation, collecting it in low points (sumps), and pumping it out continuously. This is the simplest and least expensive approach and works adequately when the inflow rate is low and the soil is not destabilized by the seepage. The pumps run continuously throughout the excavation and foundation phase, which on a hillside project can be two to six months. On sites with higher inflow rates or where seepage is destabilizing the excavation walls, a wellpoint system may be required. Wellpoints are small-diameter perforated pipes installed at close spacing around the perimeter of the excavation, connected to a header pipe and vacuum pump that draw the water table down below the working level before excavation begins. Wellpoint systems are more expensive to install and operate but provide a controlled, pre-drained excavation rather than a reactive one.

For deep excavations with significant groundwater - subterranean basements in Malibu's coastal zone, sites near natural springs in the Santa Monica Mountains - deep well dewatering may be necessary. This involves drilling a series of wells around the excavation perimeter, each equipped with a submersible pump that draws the water table down in a cone of depression around the site. Deep well systems can achieve drawdowns of 30 feet or more, but the cost is substantial: $75,000 to $150,000 for installation alone, plus ongoing pumping costs of $5,000 to $15,000 per month.

Regardless of method, all dewatering discharge on construction sites in Los Angeles County requires compliance with the Regional Water Quality Control Board's General NPDES Permit (Order No. R4-2023-0429, NPDES No. CAG994004) for construction dewatering discharges to surface waters. The permit requires a Notice of Intent filed before discharge begins, water quality sampling within the first hour of discharge and daily thereafter for continuous operations, and compliance with effluent limitations for pH, total suspended solids, and other parameters depending on the receiving water body. Discharge cannot be directed onto neighboring properties or into the street without approval. On hillside sites, the discharge point is typically a storm drain inlet or an approved surface water connection, and the discharge must be filtered and tested before release. Permit violations carry significant fines, and the permit compliance paperwork is one of the administrative items the CM manages throughout the dewatering operation.

The cost impact of dewatering extends beyond the direct cost of the pumping system. Wet conditions slow every operation they touch: excavation is slower in saturated soil, forming and rebar placement cannot proceed in standing water, concrete placement may require tremie methods at a 15 to 25 percent cost premium, and compaction testing of backfill is complicated by moisture content that exceeds optimum. A dewatering system that keeps the excavation dry before the foundation crew arrives eliminates these cascading delays. On a project where dewatering is needed, the cost of the system is almost always less than the cost of working in wet conditions without it.

On hillside sites in the Santa Monica Mountains, Hollywood Hills, and Malibu, debris flow is a hazard that directly affects geotechnical design and foundation decisions. A debris flow is not a slow-moving mudslide. It is a fast-moving slurry of water, soil, rock, and vegetation that can travel faster than a person can run and carry enough force to destroy structures. The risk is highest on slopes that have been recently burned by wildfire - vegetation that holds soil in place is gone, and even modest rainfall can trigger a flow - but debris flow hazards exist on any steep slope with loose surface material, fractured bedrock, or inadequate drainage. The January 2025 Palisades and Eaton fires created debris flow risk zones across thousands of parcels in areas where residential construction is actively underway or planned.

The geotechnical report for a hillside property will typically identify whether the site is within or adjacent to a mapped debris flow hazard zone. The California Department of Conservation maintains debris flow susceptibility maps, and the LA County Department of Public Works issues debris and mudflow potential forecasts for recent burn scar areas. When a site is identified as having debris flow risk, the geotechnical engineer's recommendations may include setbacks from flow paths, deflection structures, debris catchment systems, or foundation designs that account for lateral debris loading.

The most sophisticated debris flow mitigation systems used in residential hillside construction are flexible ring net barriers - engineered catchment structures that absorb and contain debris flows using high-tensile galvanized steel wire mesh with integrated brake rings (energy dissipation elements) that deform progressively under load rather than failing catastrophically. These systems, manufactured by companies like Geobrugg, are anchored to micropile or grouted anchor foundations and supported by steel posts or span between rock anchors on opposing canyon walls. The ring net allows water to pass through while capturing the solid material - functioning as a giant engineered catchment fence. The brake rings absorb the kinetic energy of the debris impact, and the flexible net deforms to distribute the load across the entire anchor system.

Installing a debris flow barrier on a residential site is a significant engineering and construction undertaking. The micropile foundations that support the posts must be designed for the lateral loads imposed by a debris flow event, which can exceed 60 to 180 kilonewtons per square meter of barrier face. The anchor system - typically grouted rock anchors or soil nails extending 15 to 30 feet into competent material - must be proof-tested before the barrier is tensioned. The barrier height, span, and retention volume are engineered to match the specific debris flow scenario identified in the geotechnical hazard assessment. On projects where we have built these systems, the cost has ranged from $150,000 to over $500,000 depending on the span, the height, the foundation conditions, and the access constraints. The barrier must also be maintained: debris that accumulates must be cleared after each event, brake rings that have deformed must be inspected and potentially replaced, and the net must be checked for damage.

Even on sites where a full debris flow barrier is not warranted, the geotechnical engineer may recommend debris deflection walls (reinforced concrete or masonry walls designed to redirect flow around a structure, engineered similarly to the retaining walls covered elsewhere on this site), debris catchment basins (excavated areas upslope of the building designed to absorb and contain flow material), or simply increased foundation setbacks from identified flow paths. These recommendations become part of the grading plan and must be built as specified. Ignoring debris flow recommendations in the geotechnical report is not an option: LADBS will not issue a grading permit without the engineer's sign-off that all hazard mitigation measures are incorporated into the plans.

The foundation system recommended by the geotechnical and structural engineers is a direct response to site conditions. There is no universally "better" system - only the system that correctly matches the soil, the loads, and the constraints of a specific project. What follows is a practitioner's walk-through of the systems we most commonly encounter on residential projects in Los Angeles, with the operational detail and cost reality that owners and architects need to understand.

Spread footings are the baseline residential foundation system: continuous or isolated concrete footings that bear directly on the soil at relatively shallow depth. When soil conditions allow it - good bearing capacity at 18 to 36 inches below grade, relatively flat topography, no significant fill issues, low to moderate expansion index - spread footings are the most economical foundation system available. They are simple to form, straightforward to inspect, and fast to pour. A typical spread footing on a flat residential lot in LA is 12 to 24 inches wide and 12 to 18 inches deep, with continuous footings running beneath bearing walls and isolated pad footings beneath column loads.

The limitations of spread footings become apparent on hillside sites or on lots with variable soil conditions. Spread footings require bearing at a consistent depth across the entire building footprint. If the geotechnical report indicates that competent bearing material is at 3 feet in one area and 12 feet in another, spread footings either need to be massively deepened in the weak zone (at significant cost) or the design needs to transition to a system that can bridge variable conditions. Similarly, spread footings on slopes must be set back from the slope face per the geotechnical engineer's recommendations, which can consume buildable area or require the footing to step down with the slope at considerable additional cost.

For a typical 4,000 square foot house on a flat lot in Los Angeles with good bearing conditions, spread footing costs range from $60,000 to $120,000, including excavation, formwork, reinforcing steel, concrete, and backfill. That range reflects variations in footing size (driven by load and soil capacity), soil conditions, and the complexity of the floor plan layout.

When bearing conditions are variable across the site or when moderate slopes create differential footing depths, the structural engineer often specifies grade beams supported by drilled piers. This system uses reinforced concrete beams (grade beams) that span between piers drilled to competent bearing material. The grade beams distribute the building load to the piers, and the piers transfer that load to the bearing stratum below.

Drilled piers in this configuration are typically 18 to 30 inches in diameter and 10 to 30 feet deep, depending on where adequate bearing is found. The grade beams connecting them are typically 12 to 24 inches wide and 24 to 48 inches deep, heavily reinforced with continuous top and bottom rebar. This system handles differential settlement well because each pier bears independently on competent material, and the grade beams are designed to span between piers if any localized settlement occurs.

For a 4,000 square foot house on a lot with variable conditions, a grade beam and pier system typically costs $150,000 to $350,000, depending on the number and depth of piers, soil conditions encountered during drilling, and whether groundwater is present.

The caisson and grade beam system is the foundation that most hillside projects in Los Angeles ultimately require. If your site is in the hills of Bel Air, upper Beverly Hills, Pacific Palisades, Malibu, or the Hollywood Hills, there is a strong probability that your structural engineer will specify caissons. This section is the most detailed in this guide because caisson construction is where the most money is spent, the most complexity is encountered, and the most things can go wrong.

A caisson (also called a drilled shaft or drilled pier at larger diameters) is a cylindrical reinforced concrete column cast in place in a drilled hole. On residential hillside projects in LA, caisson diameters typically range from 24 to 48 inches, with depths from 15 feet to over 60 feet depending on how far down competent bearing material or bedrock is located. A typical hillside house might require 15 to 40 caissons, connected by a grid of grade beams that supports the structure above.

The drilling operation begins with mobilizing a drill rig to the site. On hillside lots, access is often the first constraint - narrow streets, steep driveways, overhead utility lines, and limited staging area all dictate what equipment can be used. A standard truck-mounted drill rig needs a reasonably flat pad to operate from, and that pad must be graded before drilling begins. In tight-access situations, a smaller track-mounted rig or a limited-access rig (which can operate in spaces as narrow as 36 inches of horizontal clearance and 8 feet of vertical clearance) may be required, at a significant cost premium over standard equipment.

Each caisson hole is drilled using an auger or bucket auger, and the spoils (excavated earth) must be removed from the site. On a hillside project with 30 caissons at 36 inches in diameter and 40 feet deep, the spoils volume is approximately 300 to 400 cubic yards - roughly 30 to 40 truckloads. Those trucks must navigate hillside streets, comply with haul route approvals, and operate within restricted hours. Spoils handling and hauling is one of the most underestimated costs in hillside foundation work, and on difficult sites it can add $50,000 to $150,000 or more to the foundation budget.

Once a hole is drilled to the target depth and the geotechnical engineer has confirmed bearing by observing the bottom of the hole (or by reviewing cuttings and correlating with the boring data), a steel reinforcing cage is lowered into the hole. A typical 36-inch caisson might contain a cage with 8 to 12 vertical #10 or #11 bars with #4 spiral ties at 6 inches on center. The cages are fabricated on site or delivered pre-fabricated and can weigh 2,000 to 5,000 pounds each, requiring a crane for installation. After the cage is set and inspected by the special inspector (who verifies bar size, spacing, lap lengths, and cage positioning), concrete is placed.

Standard concrete placement in a dry hole is by free-fall from a concrete pump or directly from the truck chute, with the concrete vibrated as it fills to eliminate voids. If the hole has groundwater, the method changes to tremie placement as described in the groundwater section above. Concrete for caissons is typically 4,000 to 5,000 PSI with a 3/4-inch maximum aggregate, though tremie placement may require higher-slump mixes with small aggregate to ensure proper flow and displacement of water. A single 36-inch by 40-foot caisson requires approximately 7 to 8 cubic yards of concrete.

When you hit rock during drilling - which is the goal, since bedrock is typically the target bearing material - the operation slows significantly. Drilling through fractured or weathered rock requires rock augers or core barrels. Drilling through hard, competent rock may require a downhole hammer. The geotechnical report will specify a minimum embedment into rock (typically 2 to 5 feet), and the production rate through rock can drop from 5 feet per hour in soil to less than 1 foot per hour in hard rock. Rock drilling adds cost, but it also provides the most reliable bearing.

For a hillside house in Los Angeles requiring a caisson and grade beam foundation, the typical cost range is $400,000 to $1.2 million or more. That wide range is driven primarily by the number and depth of caissons, the presence of groundwater, the type of material being drilled through, access constraints, and spoils handling logistics. A relatively straightforward hillside site with 20 caissons to 25 feet in dry conditions might be at the lower end. A complex site with 35 caissons to 50 feet, wet conditions, rock drilling, and limited access will be at the upper end or beyond.

Helical piers are steel shafts with helical plates welded to the shaft that are screwed into the ground using hydraulic torque motors. They are an excellent solution for specific conditions: additions to existing structures where vibration must be minimized, tight access situations where a drill rig cannot reach, sites with high water tables where drilling would be impractical, and retrofit applications where an existing foundation needs supplemental support.

The advantages of helical piers are significant in the right context. Installation produces no spoils (no trucks, no hauling), generates minimal vibration (critical when working adjacent to an existing structure), and can be performed inside existing buildings with low headroom. Capacity is verified during installation by correlating installation torque with load capacity, providing real-time confirmation that each pier is performing as designed.

The limitations are equally important. Individual helical pier capacity is lower than a large drilled caisson - typical residential helical piers are rated for 25 to 75 kips, while a 36-inch caisson can carry 200 kips or more. Helical piers cannot be installed effectively in dense rock, cobble zones, or heavily cemented soils, because the helical plates cannot advance through hard material. And for new construction with heavy concentrated loads, the number of helical piers required to match the capacity of a caisson system may make the economics unfavorable.

Helical pier installation for residential applications in LA typically costs $800 to $2,500 per pier installed, depending on shaft diameter, depth, and access conditions. For a foundation retrofit or an addition to an existing hillside home, a helical pier system might cost $80,000 to $250,000.

When the geotechnical report indicates expansive soils with an expansion index (EI) above 50, the structural engineer will typically specify either a post-tensioned (PT) mat slab or deepened footings with void forms. The PT slab is the more common solution for new construction in LA on flat or gently sloped sites with expansive clay soils.

A post-tensioned slab distributes the building load across the entire footprint rather than concentrating it at footing lines. The slab is reinforced with high-tensile steel tendons (typically 1/2-inch, 7-wire, 270 ksi strand) sheathed in plastic and placed in a grid pattern through the slab before the pour. After the concrete cures for three to seven days, each tendon is stressed with a hydraulic jack to a specified force - typically 33,000 pounds per tendon - which places the entire slab in compression. This compression counteracts the tensile forces that expansive soil movement would otherwise create, preventing the cracking that destroys conventional slabs on expansive soil.

PT slab construction requires coordination that spread footings do not. The post-tensioning contractor is a specialty subcontractor who lays out and installs the tendon system, performs the stressing operation, and cuts and caps the tendon tails. All plumbing that penetrates or passes through the slab must be installed before the pour and must be sleeved to allow the slab to move independently of the plumbing. Because the tendons cannot be cut after stressing without compromising structural integrity, any future modifications to the slab (plumbing reroutes, new penetrations) require scanning to locate tendons and careful planning to avoid them. Per CBC Section 1805.8, foundations on expansive soils with an EI greater than 20 require a special foundation design, and the PT method per the Post-Tensioning Institute (PTI) specifications is one of two accepted approaches.

For a 4,000 square foot PT slab foundation on a flat lot in LA, costs typically range from $100,000 to $200,000, depending on slab thickness, tendon density, soil conditions, and plumbing complexity. The PT system itself (tendons, stressing, anchorage hardware) adds approximately $3 to $6 per square foot over a conventional slab.

For moderately expansive soils (EI of 20 to 50, roughly), deepened footings with void forms offer an alternative to the PT slab. The concept is straightforward: place the footing bottoms below the "active zone" - the depth at which moisture content fluctuates seasonally (typically 3 to 5 feet in LA soils) - and isolate the grade beams from the expansive soil using cardboard void forms (trade name: Carton Form or similar) that compress and deteriorate over time, creating an air gap that allows the soil to swell without pushing against the structure.

This system works well when the expansion index is moderate and the site allows for deeper footings without encountering groundwater or other complications. The cost falls between spread footings and a PT slab, typically $80,000 to $150,000 for a 4,000 square foot house, depending on the required footing depth and site conditions.

The table below summarizes the key characteristics and cost ranges for each foundation system as applied to a typical 4,000 square foot residential project in the Los Angeles market. These are planning-level ranges based on our project experience. Actual costs depend on site-specific conditions, and the geotechnical report is the document that determines which system is appropriate for a given site.

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Getting concrete to the pour location on a hillside site is a logistics challenge that flat-lot construction never encounters. A standard concrete mixer truck holds 8 to 10 cubic yards and weighs approximately 66,000 pounds fully loaded. It requires a reasonably flat, stable surface to set up and pour from, and the chute that extends from the back of the truck reaches approximately 12 to 18 feet. On a hillside project where the foundation is 40 feet below the street, or where the driveway is too narrow or steep for a loaded truck, direct chute pour is not an option. A concrete pump is required.

Boom pump trucks are the standard solution. A truck-mounted boom pump sets up on the street or on a staging pad and extends an articulated boom arm - typically 32 to 52 meters on trucks used in residential work - that can reach over houses, down hillsides, and into excavations that no mixer truck could access. The boom pump requires a level setup area large enough for the truck and its outriggers, which can span 20 to 30 feet. On narrow hillside streets, finding that setup area and coordinating with neighbors about temporary access is part of the preconstruction logistics plan. Boom pump rental for a foundation pour typically runs $1,500 to $3,500 per day, and a large caisson and grade beam pour may require two or three days of pumping.

For sites where even a boom pump cannot reach - extreme access constraints, very deep excavations, or locations where no truck can stage within boom reach - a line pump with extended hose runs is the fallback. Line pumps push concrete through a 4- or 5-inch diameter hose that can be run hundreds of feet, around corners, and down slopes. The production rate is slower than a boom pump, the hose runs require setup and cleanup labor, and blockages in long hose runs can shut down a pour mid-stream. Line pumping adds cost and risk, but on sites with severe access limitations, it is the only option.

Pour sequencing on a large grade beam network requires advance planning. A typical hillside house with 25 to 35 caissons connected by grade beams might require 150 to 250 cubic yards of concrete for the grade beam system alone - roughly 15 to 25 truckloads. Those trucks need to arrive at timed intervals that match the pump's output rate, navigate hillside streets within restricted hauling hours, and maintain continuous concrete delivery so the pour does not develop cold joints (interruptions that create structural weak points in the concrete). The CM develops the pour plan: the sequence of grade beams, the number of trucks required, the pour rate, the mixer truck dispatch schedule, the labor crew assignments for vibrating, screeding, and finishing, and the contingency plan if a truck is late or the pump goes down.

Weather affects concrete placement directly. In hot weather (above 90 degrees, which is common during LA summers), accelerated cement hydration can cause the concrete to set before it is properly placed and finished. Hot weather concrete precautions include reduced batch-to-discharge time (typically 60 minutes maximum), ice in the mix water to lower concrete temperature, retarding admixtures to slow set time, and early-morning pour starts to avoid peak heat. In cold or wet weather - less common but not rare in LA winters - the concern reverses: concrete that does not reach adequate strength before freezing or that becomes diluted by rain during placement may not achieve its design strength. A surprise rainstorm during a pour can compromise the entire placement if the crew cannot cover and protect the fresh concrete. The CM monitors weather forecasts during pour week and makes the go/no-go call the morning of the pour.

Any time construction requires a vertical or near-vertical cut into the earth - for a basement, a retaining wall footing, a foundation below grade on a hillside - the question of shoring arises. The geotechnical report specifies the maximum height and angle of temporary unshored cuts, and any excavation that exceeds those limits requires a shoring system designed by a licensed engineer.

On hillside residential projects in LA, shoring is nearly always required. The building pad is typically cut into the hillside, creating a vertical or near-vertical face on the uphill side that cannot stand unsupported. The retaining walls that will eventually hold the earth back are part of the permanent structure, but they cannot be built until the excavation is complete - and the excavation cannot be held open without temporary shoring. This sequencing reality is one of the things that makes hillside construction fundamentally different from building on a flat lot.

The simplest and cheapest approach is to lay the excavation back at a stable temporary slope - typically 1:1 (45 degrees) or 1.5:1, depending on the geotechnical report's recommendations. This avoids the cost of a shoring system entirely, but it requires adequate setback from property lines and adjacent structures. On a hillside lot that is 60 feet wide with a neighbor's house 10 feet from the property line, laying back a 15-foot cut at 1:1 would consume 15 feet of lateral space that usually is not available. Open cut works on larger sites with generous setbacks. On most hillside residential lots in LA, it is not a viable option for the primary excavation.

Soldier pile and lagging is the most common temporary shoring system on residential hillside projects in Los Angeles. Steel H-piles (typically W8x48 or W10x49 sections) are drilled into the ground at 6- to 8-foot spacing along the excavation line, embedded in lean-mix concrete backfill. As excavation proceeds downward in 4- to 5-foot lifts, horizontal timber lagging (typically 3- to 4-inch rough-cut Douglas fir) is installed between the pile flanges, creating a continuous wall that retains the earth behind it.

The system works well for cuts up to approximately 12 to 15 feet without lateral support. For deeper cuts, or where soil conditions are poor, surcharge loads from adjacent structures are significant, or where deflection must be minimized to protect neighboring improvements, the soldier piles are supplemented with tiebacks.

Tiebacks (also called ground anchors) are steel tendons drilled at a downward angle through the shoring wall and into the retained earth or rock behind it. The tieback is grouted in place, stressed to a design load using a hydraulic jack, and locked off against a bearing plate on the face of the soldier pile. Each tieback provides active lateral resistance to the shoring wall, allowing the system to support deep cuts, heavy surcharge loads, and difficult soil conditions.

Tieback installation is a drilling operation in its own right. A small drill rig works from within the excavation, drilling 20- to 40-foot holes at 15 to 30 degrees below horizontal. The tieback tendon is installed, grouted, and stressed after the grout cures. Each tieback must be proof-tested to 133 percent of design load to verify performance before being locked off.

On typical hillside lots with 5- to 10-foot side yards, tiebacks almost certainly cross into the neighbor's property below grade, requiring a subsurface easement per LAMC Section 91.7006.5. If the neighbor refuses, the shoring design must change to a system that stays within the property line - internal bracing, rakers, or soil nails - at significantly higher cost. We have seen unresolved tieback easement issues add three to six months and $150,000 or more to a project. Our retaining walls page covers tieback easement negotiations, California Civil Code Section 832 requirements, and alternative shoring strategies in detail.

Pipe and board (sometimes called CISS piles with lagging) uses steel pipe piles instead of H-piles, with board lagging installed between them. This system is used in tight-access situations where a full-sized drill rig cannot reach, in vibration-sensitive areas where driven piles are not appropriate, and where the shoring layout requires smaller-diameter piles at closer spacing. The cost is comparable to or slightly higher than soldier pile and lagging, and the applications overlap significantly. Selection between the two typically depends on access constraints and the shoring engineer's preference for the specific site conditions.

Temporary shoring is designed to hold the earth during construction and is intended to be removed or abandoned once the permanent retaining structure is in place. In practice, removal of soldier piles is often impractical once the permanent wall is built against them, so the shoring is frequently left in place and incorporated into the permanent structure. When this is the design intent from the beginning - and it often should be - the shoring system must be designed and detailed as permanent from the start, with appropriate corrosion protection for the steel and structural detailing that integrates with the permanent retaining wall.

Shoring costs on residential hillside projects in Los Angeles vary widely depending on the system type, the cut height, the soil conditions, and whether tiebacks are required. For a typical hillside project with 100 to 200 linear feet of shoring face at 10 to 20 feet in height, the ranges below provide planning-level expectations.

Foundation construction involves more consultant and trade coordination than any other phase of a residential project. During the framing phase, the general contractor primarily coordinates with the framing crew, the structural engineer (for field questions), and inspectors. During the foundation phase, the active team includes the geotechnical engineer, the structural engineer, the civil engineer, the architect, the construction manager, the shoring contractor, the foundation drilling contractor, the concrete subcontractor, the plumbing contractor, the soils testing laboratory, and the special inspector. All of these parties must be aligned on scope, sequence, and timing, and the consequences of miscoordination during foundation work are permanent.

Concrete does not forgive. Once it is placed, the only options for correcting errors are demolition and replacement (expensive, time-consuming, and structurally inferior to getting it right the first time), core drilling for missed penetrations (which cuts through reinforcing steel and weakens the section), or field modifications that compromise the original design intent. The coordination standard during foundation work must be higher than any other phase because the tolerance for error is essentially zero.

The examples below are not hypothetical. They are real coordination failures we have either encountered directly or observed on projects we were brought in to help recover. Every one of them was preventable with proper preconstruction coordination.

Plumbing sleeves missed before foundation pour. The plumber did not install underslab sleeves before the concrete was placed. Now the only option is to core-drill through the new foundation to run waste and supply lines. Core drilling through reinforced concrete costs $500 to $2,000 per penetration, takes days to coordinate with the structural engineer (who must approve the location and confirm it does not compromise reinforcement), and every core cut through rebar reduces the structural capacity of the member. On a PT slab, an accidental tendon strike during coring can release 33,000 pounds of stored energy and compromise the entire slab section. The cost of this error: $15,000 to $50,000 in remediation and two to four weeks of delay.

Bearing not verified before pour. The foundation contractor placed concrete in footing excavations without the geotechnical engineer present to observe and verify bearing. LADBS requires soils engineer observation at bearing for all structural footings. Concrete placed on uncertified bearing material may need to be removed and replaced if the soils engineer, after the fact, cannot certify the conditions. Removal of freshly placed concrete from a footing trench is a destructive, expensive process. The cost: $30,000 to $100,000 or more in removal, replacement, and delay, depending on how much concrete was placed before the error was caught.

Shoring layout conflicts with footing locations. The shoring piles were installed based on a plan that did not account for the final footing locations. When excavation was completed, three soldier piles were directly in the path of continuous footings. The options were to modify the footing layout (requiring structural redesign and re-approval), remove and relocate the shoring piles (requiring shoring redesign and re-installation), or design the footings around the piles (compromising the structural system). Each option costs money and time. The root cause was that the shoring engineer and the structural engineer did not coordinate their respective layouts during design.

Anchor bolt layout does not match steel shop drawings. Anchor bolts were cast into the concrete foundation per the structural plans, but the steel fabricator's shop drawings showed different column base plate dimensions and bolt patterns. The bolts as cast cannot accept the steel columns as fabricated. Options include field-modifying the base plates (requires structural engineer approval, reduces connection capacity), removing and re-setting anchor bolts using epoxy anchors (structurally inferior to cast-in-place bolts), or chipping out concrete and re-pouring with correct bolts (expensive, time-consuming). The cost: $20,000 to $75,000 and three to eight weeks of delay on steel erection.

The matrix below shows how key geotechnical findings map to design decisions, team coordination requirements, and cost and schedule impacts. This is the type of coordination document we develop during preconstruction to ensure that every finding in the geotechnical report has a responsible party, an action item, and a timeline. When a geotechnical finding is identified that affects multiple parties, this matrix prevents it from falling through the cracks.

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The foundation does not exist in isolation. It interfaces with every system that passes through it, sits on it, or connects to it. Each of these interfaces has a specific timing window during construction, and most of them have zero tolerance for error. Missing the window means the interface must be addressed after the fact, which is always more expensive, slower, and structurally inferior to getting it right during the original installation. Managing these interfaces is one of the core functions of a construction manager during the foundation phase.

Every waste line, supply line, and conduit that passes through or under the foundation must be installed or sleeved before the concrete pour. There is no going back. On a slab-on-grade foundation, underslab plumbing is installed after the sub-grade is prepared and before the concrete is placed. The plumber must work from the structural plans and the plumbing plans simultaneously to ensure that every penetration is in the right location and that sleeves are large enough to accommodate pipe movement and thermal expansion.

On a caisson and grade beam system, the critical coordination point is the grade beam penetrations. The structural engineer specifies where penetrations are allowed (typically at mid-span, away from bearing points and high-moment zones) and what sleeve sizes are acceptable. The plumber and the structural engineer must coordinate these locations before the grade beam rebar is fabricated, because once the cage is tied and set in the forms, adding a sleeve means cutting rebar, which requires structural engineer approval and may require supplemental reinforcing.

On a post-tensioned slab, the plumbing coordination is even more critical. Tendons run through the slab in a grid pattern, and any penetration must be located between tendons. The PT contractor provides a tendon layout drawing, the plumber provides a penetration plan, and the two must be reconciled before the pour. If a penetration cannot be located between tendons, the tendon layout must be adjusted (which requires structural engineer approval) or the plumbing must be rerouted. This coordination must happen during shop drawing review, weeks before the concrete pour.

Below-grade waterproofing is applied to the exterior face of foundation walls after the concrete has cured and before backfill is placed. The timing window is narrow: the concrete must be cured sufficiently to receive the waterproofing membrane (typically 7 to 14 days depending on the system), the surface must be clean and dry, and the waterproofing must be fully cured and inspected before any earth is placed against it. Weather matters. A surprise rainstorm during the waterproofing window can delay application by days and expose uncured concrete to moisture infiltration.

On hillside projects with retaining walls and below-grade living spaces, the waterproofing system is not optional and it is not a place to cut costs. A failed waterproofing membrane buried under compacted backfill is catastrophically expensive to repair - remediation costs of $200,000 to $500,000 are not uncommon. Our retaining walls page covers waterproofing sequencing in detail, including blindside membrane applications where shoring prevents access to the earth-side face.

When the structural system above the foundation is structural steel, anchor bolts cast into the concrete foundation must align precisely with the column base plate bolt patterns shown on the steel fabricator's shop drawings. The tolerance is tight - typically plus or minus 1/8 inch on bolt location and plus or minus 1/4 inch on the bolt group. This means the anchor bolt template must be built from the approved shop drawings (not the structural plans, which may have been revised during the shop drawing process), set in the formwork with precision, and checked before and during the concrete pour.

The shop drawings are the controlling document. If the structural plans show one base plate configuration and the shop drawings show a different one (because the fabricator revised the connection during engineering), the anchor bolts must match the shop drawings. This is a coordination item that the CM must track: shop drawing approval must be complete before anchor bolt templates are built, and any revisions to base plate details after anchor bolt installation require immediate notification and field resolution.

This interface occurs after the foundation phase but is planned during it. Shear walls - walls that provide lateral resistance to seismic and wind loads - cannot have penetrations. Period. No plumbing pipes, no HVAC ducts, no electrical conduits can pass through a designated shear wall unless the structural engineer has specifically designed that penetration into the wall. The framing plan identifies shear wall locations, and the MEP routing must be planned around them.

On a complex hillside home with multiple levels, the number of shear walls is significant, and the routing constraints they create must be identified during design development, not during rough-in. When a plumber or electrician discovers in the field that their planned route passes through a shear wall, the options are all bad: reroute (costly, may require opening finished surfaces), get structural approval for a penetration (may not be possible without supplemental reinforcing), or modify the shear wall system (requires structural redesign). This is a preconstruction coordination issue, and the CM's job is to ensure it is resolved on paper before it becomes a field problem.

Every retaining wall requires a drainage system behind it. Without drainage, hydrostatic pressure builds against the wall, adding loads that the wall was not designed to resist. The subdrain system - typically a 4-inch perforated pipe wrapped in filter fabric, bedded in gravel - must be installed at the base of the wall before backfill and must drain to daylight or to a sump pump system. Most residential retaining walls are designed for drained conditions, which means the subdrain must function for the life of the structure. Our retaining walls page covers drainage system design, failure mechanisms, French drain specifications, and the hydrostatic forces that develop when drainage fails.

On a hillside site, every grading and foundation decision changes how water moves across the property, and those changes carry both engineering consequences and legal liability. Per LAMC Section 91.7013, all slope drainage must be collected and disposed of through approved drainage devices - interceptor terraces, down drains, swales, and catch basins - designed to convey flows based on the 50-year isohyetal rainfall calculation prepared by a California-licensed civil engineer. Where those drainage devices discharge onto natural ground, the code requires velocity reducers, diversion walls, riprap, concrete aprons, or similar energy dissipators to prevent erosion at the point of discharge. This is not optional. LADBS plan check will reject grading plans that show drainage outlets without appropriate energy dissipation.

Riprap - broken rock placed at drainage outlet points - is the most common energy dissipator on residential hillside sites. The grading plan must specify the riprap class and rock size, and the civil engineer's drainage calculations must demonstrate that the outlet velocity is reduced to a level that prevents erosion of the receiving surface. The plan must show the riprap in cross-section detail: the thickness of the rock layer, the length of the riprap apron, and the embedment depth. Where channel flow needs to be converted to sheet flow before discharge - common at the toe of a slope where concentrated drainage must be dispersed across a broader area - LAMC Section 91.7013.7 requires a drainage dispersal wall constructed per Figure F of the grading code. These are low concrete walls with a specific geometry that spreads the flow laterally before it leaves the improved area.

The legal dimension of surface drainage is as important as the engineering. California follows a modified civil law rule for surface water, established in Keys v. Romley (1966): a property owner who alters the natural drainage pattern is liable to neighboring property owners for any resulting damage, subject to a reasonableness standard. The court evaluates whether the alteration was necessary, whether it was carried out in a reasonable manner, and whether the benefit to the altering property outweighs the harm to others. On a practical level, this means that any hillside construction project that changes how water flows across, through, or off the property creates potential liability for the owner if that altered flow damages a neighbor's property downstream.

The grading code enforces this principle directly. Per LAMC Section 91.7006.5, any proposed construction that changes or alters the existing drainage pattern to adjacent property requires a notarized and recorded offsite drainage release covenant or easement from the owner of the adjacent property. In LA County's unincorporated areas, the same requirement applies through the County grading review process - if the project increases flow or volume onto neighboring property and that increase cannot be mitigated or retained on site, a recorded drainage covenant is required before plan check approval. This is the drainage equivalent of the tieback easement problem: a neighbor negotiation that must be resolved during preconstruction, not during construction.

The CM's role in surface drainage management is coordination between the civil engineer (who designs the drainage system), the geotechnical engineer (whose report identifies slope stability constraints and soil erodibility), the grading contractor (who builds the drainage devices), and LADBS or County plan check (who reviews and approves the drainage plan). Roof drainage must discharge at least 5 feet from foundation walls per County code. Subdrains are required under all fills placed in natural watercourses. Clean-outs are required every 50 feet on residential closed drain runs. Every drainage device shown on the grading plan must be built as designed, and deed restrictions for private maintenance of drainage devices are recorded against the property before final approval. When these systems are designed and built correctly, they protect both the structure and the owner's long-term liability exposure. When they are not, the consequences are measured in slope failures, neighbor disputes, and remediation costs that can exceed the original drainage system cost by a factor of ten.

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The cost ranges below reflect Los Angeles luxury residential market pricing as of early 2026. They are drawn from our direct project experience managing foundation work on complex sites across Beverly Hills, Bel Air, Pacific Palisades, Malibu, and the Westside. These are not national averages from cost databases. They represent what you will actually pay when you hire qualified contractors to do this work on difficult residential sites in Los Angeles.

On a flat residential lot in Los Angeles with straightforward soil conditions, the combined foundation-related cost (geotechnical investigation, foundation, waterproofing, earthwork, testing, and inspection) typically runs 8 to 12 percent of total construction cost. On a hillside site with challenging conditions, that figure climbs to 15 to 25 percent. For a comprehensive breakdown of how foundation costs fit within the full budget structure of a luxury residential project, see our construction cost guide. The premium is almost entirely driven by site conditions - the structure above contributes the same gravity loads regardless of whether it sits on a flat lot or a hillside. The difference is what is required to transfer those loads to competent bearing material through difficult, variable, and often wet ground.

The false economy in foundation work is value-engineering the investigation or cutting corners on execution. A thinner geotechnical report saves $5,000 to $10,000 and misses the fill layer that costs $400,000 to address in the field. A less experienced drilling contractor saves $30,000 on the caisson bid and produces holes that are off-location or underdrilled, requiring redesign and supplemental work. Foundation work is the one area of a residential project where spending less almost always costs more in the long run, because the consequences of inadequate investigation or poor execution are permanent, buried, and extraordinarily expensive to remediate.

The construction manager's role during the foundation phase is to translate technical information into actionable construction decisions, coordinate between multiple engineers and trade contractors, develop logistics plans for complex operations, manage field verification during construction, and handle the inevitable surprises when actual conditions differ from what the geotechnical report predicted.

The geotechnical report is written by engineers for engineers. It communicates in the language of bearing capacity, lateral earth pressure coefficients, and seismic site classification. Most owners and many architects do not read geotechnical reports, and the critical information buried in the recommendations section can be easily overlooked. We review every geotechnical report we receive and translate it into plain language for the owner and design team: what the ground conditions are, what they mean for foundation cost and schedule, what risks exist, and what decisions need to be made. This translation is not a simplification. It is a reorganization of technical information into the framework of construction planning.

From the geotechnical report, we develop the coordination matrix shown in Section 5. Every finding that affects design, cost, or schedule is mapped to the responsible party, the required action, and the timeline. This matrix becomes the tracking document through preconstruction and into construction, ensuring that nothing falls through the cracks between the geotechnical engineer's recommendations and the structural engineer's design, between the structural design and the trade contractor's execution, and between the design intent and the field conditions.

Foundation work on hillside sites requires detailed logistics planning that goes far beyond what is needed on a flat lot. The site development phase sets the stage for everything that follows. The drill rig needs a stable, level pad to operate from, and on a sloped site, that pad must be graded before drilling begins. The pad location determines the sequence of drilling - which caissons can be reached from which pad position - and that sequence determines the overall drilling schedule. Spoils must be stockpiled (if space exists) or loaded directly onto trucks for immediate export. Concrete trucks must be able to reach the pour location, and on narrow hillside streets, a concrete pump may be required because the trucks cannot get close enough to pour directly. Each of these logistics decisions affects cost and schedule, and they must be planned in advance, not resolved in the field.

Haul route planning for spoils and concrete delivery requires coordination with LADBS (for haul route approval), the Department of Transportation (for any street use or lane closure permits), and often the local neighborhood council or homeowner association (for community notification of truck traffic). Hauling hours on hillside streets in LA are typically restricted to 9:00 AM to 3:00 PM, Monday through Friday. A foundation operation that generates 40 truckloads of spoils and requires 50 truckloads of concrete delivery, all within a limited daily hauling window, requires careful scheduling to avoid bottlenecks and to minimize disruption to the neighborhood. These logistics constraints directly affect the overall construction timeline.

During construction, we manage the field verification process that confirms actual conditions match the geotechnical report's predictions. At every footing and caisson location, the geotechnical engineer must observe the bearing material and confirm it meets the report's specifications before concrete is placed. We schedule these observations, coordinate access for the engineer, and ensure the inspections happen at the right time in the construction sequence.

Beyond geotechnical verification, the California Building Code (CBC Chapter 17) requires a special inspection program for structural concrete, reinforcing steel, and other critical materials on virtually every residential project in Los Angeles. All of LA falls into Seismic Design Categories D, E, or F, which triggers special inspection requirements that go well beyond the exemptions available for simple one- or two-story dwellings in lower seismic zones. In Los Angeles, special inspectors must be Registered Deputy Inspectors (RDIs) with LADBS, holding specific registrations for each inspection type: Reinforced Concrete (RC), Structural Steel/Welding (SSW), Grading (GD), and others. The RDI is employed by the owner (not the contractor), providing independent third-party verification that the work complies with the approved plans.

The special inspection hold points during foundation work are specific and non-negotiable. For reinforced concrete foundations, the RDI must be present for rebar placement verification (bar size, spacing, lap lengths, cover, chair placement), anchor bolt location and projection verification, concrete placement (verifying mix design, slump, air content, and placement methods), and post-tensioning operations on PT slabs (tendon stressing verification and elongation measurements). For cast-in-place deep foundations (caissons), the RDI must verify the rebar cage dimensions, the cage placement in the hole, and the concrete placement method. These are continuous inspection items, meaning the inspector must be present for the duration of the activity, not just at the beginning and end.

The testing program runs parallel to the special inspection program. Concrete cylinder samples are taken from every load delivered to the site - typically one set of four cylinders per 50 cubic yards or per day of pour, whichever is more frequent. The cylinders are cured and tested at 7 and 28 days by an approved testing laboratory. If the 28-day break falls below the specified strength (typically 3,000 to 5,000 PSI on residential projects), the structural engineer must evaluate whether the in-place concrete is adequate or whether remedial action is required. Rebar is sampled and tested for tensile and yield strength. Compaction testing during grading and backfill requires the soils testing lab to have personnel on site for every lift of fill placement, performing nuclear density tests to verify that each lift meets the compaction specification.

On a typical hillside project, the combined cost of soils testing, special inspection, and laboratory testing runs $25,000 to $100,000. This is not an optional line item. LADBS will not issue a Certificate of Occupancy without the final special inspection reports, and the structural engineer's observation reports must confirm that the work was constructed in conformance with the approved plans. The CM's role is to ensure the inspection and testing agencies are scheduled at the right hold points, that no work proceeds past a hold point without the required inspection, and that all reports are collected, reviewed, and filed. Missing a required inspection means either stopping work until the inspector arrives or, far worse, proceeding without the inspection and facing potential removal and replacement of unobserved work. On a $900,000 caisson and grade beam foundation, the cost of a missed inspection that requires concrete removal is measured in six figures and months of delay.

The geotechnical report is based on discrete boring locations. Between those borings, conditions are interpolated. During construction, when the actual excavation reveals what is between the borings, conditions that differ from the report are common on hillside sites. The response to these surprises must be immediate, coordinated, and documented.

When a caisson drilling crew hits unexpected conditions at 30 feet - softer material than predicted, water where none was anticipated, a boulder field that the boring 15 feet away did not encounter - the CM must coordinate the response in real time. The drill crew stops. The geotechnical engineer is called to observe. The engineer provides updated recommendations (drill deeper, change diameter, adjust bearing requirements). The structural engineer confirms the updated recommendations are structurally adequate. The CM documents the change, adjusts the cost and schedule impact, and communicates to the owner. This process happens multiple times on a typical hillside project, and the speed and quality of the response directly affects cost and schedule outcomes.

This is the value of having a construction manager who understands geotechnical engineering at a practitioner level: the ability to anticipate what might go wrong, to plan for contingencies before they become emergencies, and to coordinate the response when conditions in the ground do not match conditions on paper. Our feasibility study process and preconstruction services are designed specifically to identify and plan for these conditions before construction begins, when the cost of addressing them is measured in consultant fees rather than change orders.