Foundation construction takes many different forms. A common method of foundation support is the concrete filled, steel shell, pipe pile. This paper will guide the reader through the process of estimating the costs associated with the construction of this type of pile. Design of this pile is an example based upon the author’s prior experience. Principles of estimating the costs of construction of this type of pile is the goal of this document.
Foundation design has been performed for thousands of years. Without it, the Megalithic Temples of Malta, dating back to 3600 BC and every still-standing structure built after would not have survived. In fact, poor foundation design almost ensures the failure, potentially cataclysmic in nature, of a structure.
The earliest types of piles were fabricated from timber, placed in holes dug into the ground and backfilled with soil. Since then, improvements in construction methods and materials have been driven by the desire to build safer, cheaper, higher, and more efficiently. Over the years, new technologies have been developed and subsequently a multitude of pile types currently exist and are used throughout the world. The Cast-In-Place (or CIP) Pile, as it is commonly referred to in the industry, is the topic of this paper.
The typical CIP Pile is constructed in order to support a structure or act as some type of structure in and of itself. They are used for Building support, Bridge support, Utility support and for many other purposes.
To begin, a work area will have to be prepared. An access way may need to be constructed should the route of travel not be suitable to support the heavy equipment that will be used in this operation. This can take the form of temporary access roads made of geotextile fabric and an aggregate of some sort, or a temporary structure may be required. This is all dependent upon site conditions and design requirements.
The proposed installation area will be cleared, made reasonably flat and level. Further, any ground preparation will be performed as necessary to facilitate construction. A plethora of equipment including a crane of sufficient capacity will be brought on site along with a set of pile leads, a pile hammer, and a power source for the hammer.
Next, steel pipe pile shells would be brought on site. These piles may require splicing, which is joining of two or more sections to make a single pipe section, and installation of points on the end of the pile of some sort if required.
The pile leads will be assembled and raised to a vertical orientation by use of the crane. In certain situations, the pile could be installed on a slant. In this case, the pile leads would be held in the slanted orientation for driving of piles. This is called a “Battered Pile” and is used to combat sliding and/or overturning of a structure.
The hammer will be installed in the leads and the crane will raise it to an appropriate height. The pipe pile will then be raised by the crane until it is completely within the leads and the entire assembly will be positioned using surveyed layout information. The pile will be lowered to the ground, the hammer will be lowered upon the end of the pile, and the pile will be driven into the ground.
Once the pile is driven to the expected depth, the exposed top will be cut off. A fabricated rebar cage that will act as a connection between the pile and the proposed structure will then be installed and, in this case, the pile will be filled with concrete to provide added strength.
Types and Methods of Measurement
The following are the typical units one would encounter:
Specific Consideration Factors
INITIAL CONSIDERATIONS
The information needed to estimate accurate and detailed costs for the construction of CIP Piles would begin to be derived from construction documents provided by a licensed design engineer. These documents would consist of plans and specifications that would include where the pile(s) would be located, into what material the pile will be driven, pile capacity, what forces would be allowed to be exerted upon the pile, pile diameter, pile wall thickness, type of steel, pile top elevation(s), pile tip elevations(s), whether splices are allowed and the methods with which a splice would be made, the need for a point or end plate, the need to fill the pile and with what material, whether that material is reinforced, whether the pile is coated and if so with what material.
The methods of measurement and payment can significantly impact the pricing the Estimator must calculate in order to suitably respond to the Proposal. In many cases, due to the volatility of final pay quantities, some Project Owners will provide line items for the work in the following manner:
- Mobilize Pile Driving Equipment
- Furnish Materials for Test Piles of _ size
- Install Test Piles of _ size
- Test Piles for capacity
- Furnish Materials for Production Piles of _ size
- Install Production Piles of _ size
Should this level of detail not be able to be incorporated into the contract in some form or other, the Estimator’s risk analysis will have to incorporate said volatility of the quantities of work. It would behoove the Estimator to encourage the Proposal’s Sponsor to incorporate these line items in order to not incur substantial costs due to the associated risks.
In that the subsurface materials can vary significantly in composition, the length of a pile can vary wildly. For example, bedrock can exist in one pile location at an elevation 50 feet below grade. Five feet in any direction an underground “cliff” can exist. This is where the bedrock drops or rises substantially, and the pile driven in that location can be much longer or shorter than anticipated.
Without the above listed level of detail, pricing the work will be challenging. For example, should the production pile item consist of supply and install, and the quantity installed, being the basis of payment, should run shorter than expected, the Contractor runs the risk of having compensation reduced while expense remains the same. Should the Estimator account for an anticipated underrun of quantity and, in fact, the quantity overruns, the realized compensation may not cover the actual costs as well as overhead and profit for the work completed.
EQUIPMENT SELECTION
Many factors come into consideration when selecting equipment. It would all begin with the results of the Test Pile (discussed in the Miscellaneous Pertinent Information section below) that would dictate the order length of pile(s) and the hammer with which the pile would be driven. Both the pile length and hammer size and type would then be used to select the length of leads in which the pile and hammer would be mounted to ultimately drive the pile. All of this is used to subsequently choose the crane boom length that would place the pile hammer and leads on the proposed location, and support the hammer within the leads while lifting the pile into driving position. This can be calculated as follows:
Once the Maximum Crane Boom length is determined, one can choose the crane from manufacturer’s catalogs that would provide crane sizes that would carry the appropriately sized boom length.
Next the capacity of the crane at the appropriate radius must be calculated by the following methodology:
Total Lead weight + Total Pile Hammer weight + Total Pile Weight + Rigging = Total Load
Once the Total Load is calculated, the radius from the center of the crane at which the pile would be driven is then compared to the manufacturer’s load chart.
The total load must be less than the maximum capacity, at the maximum radius of driving in conjunction with the required boom length in order to safely lift the load according to the manufacturer of the crane. See References Section for a typical crane used in this type of work for the details mentioned herein.
It should be noted various agencies have specific safety factors that are placed upon these calculations and even though the manufacturer’s data may show safe lifting conditions, a multiplier of two times, three times or as much as five times may be mandated.
SOIL CONDITIONS
Soil Borings should be incorporated into the contract documents and should be performed in sufficient quantity and location to accurately describe the subsurface conditions on the site. Soil Borings are frequently taken with the use of an auger and a “spoon”. The auger would drill down into the soil, allowing for retrieval of samples of the soils at different levels for classification. The spoon is a device that would be placed withing the auger and blows of a certain force upon the spoon would determine the cohesivity of the soil and its ability to withstand force.
Site soil conditions can vary wildly, even within a relatively small area. Bedrock can range from depths of 5 feet below surface to 100 feet below surface within a 20 foot stretch of ground. Soil sampling can show a layer of soil that takes 3 blows to drive an auger 6 inches deep and in a stratum 5 foot below that, it could take 50 blows to drive the sample spoon 2 inches.
SPECIFIC SITE CONDITIONS
Existing site conditions as well as project staging can severely impact the productivity of construction of these piles. Should overhead obstructions of any kind exist, this will limit the length of the section of pipe pile that may be installed. This will subsequently impact the amount of work to be completed to install the pile.
Labor Availability – In some areas of the country, Unions are in control of the people that will install these piles. If a project of significant scope will be underway in the same area of the project being bid, the availability of labor may be an issue. Further, across the industry, contractors are finding it increasingly more difficult to fill job openings with skilled personnel. This can significantly impact productivity regardless of what the company’s history of performance on the scope of work has been. The potential lack of experienced personnel must be incorporated into productivity expectations as the impact to costs can be significantly more than the material itself in some parts of the country.
WEATHER
Pile driving is one of those components of a project that can take place in rain, snow, heat and cold for the most part. However, certain parts of the country do have specific weather impacts that will affect daily productivities. Lightning storms and high winds are two of these types of factors that must be considered and incorporated into the productivity of the crew.
VALUE ENGINEERING POTENTIAL
The types of piles are legion. The earliest piles were in the form of timber poles, simply placed in previously dug holes. Then stones in their natural state were piled in narrow holes to serve the same purpose. Following that, the stones were cut into shapes more suitable for stacking. Afterward, following the ability to fabricate iron and steel, shapes were derived for many structural construction purposes, and some were found to be quite efficient as foundation support.
H-Piles, Pipe Piles, Z-Piles, U-Piles and many more shapes are currently in use. Many configurations combine the available shapes to serve various construction needs. To this day, pile construction evolves and improves.
Alternatives to the designed pile should always be considered. Dependent upon contract documents, pricing said alternative sometimes may be incorporated into the estimate. In this case, the cost savings, reflected in the project pricing, could easily win the job.
Overview of Costs and Markups
Labor – The labor costs in this estimate will be based upon New Jersey Prevailing Wage Determination, in addition to payroll taxes, workers compensation, and general liability.
Equipment – The equipment rates utilized are based upon US Army Corps of Engineers document EP1110, dated 2020 escalated to today’s current rates. Ownership and operating costs will be combined.
Materials – Pricing is based upon recent information gathered from local suppliers.
Indirects – Indirect costs such as on-site project management, safety, jobsite facilities such as field offices, dumpsters and sanitary facilities will be incorporated into the estimated costs via a percentage for Overhead and Profit.
Overhead – A generalized overhead for the estimate of 10% will be used to cover costs of non-job specific supervision, home office expenses, and other similar costs to the project. The actual value is company specific and can easily vary extensively and must be calculated for the specific company’s requirements. 10% shall be used for this example.
Profit – For this example, 10% will be utilized.
All of these values would be dictated by each company bidding the work and should be derived by careful consideration and detailed mathematical backup.
Special Risk Considerations
Soils – The soil borings, when taken in sufficient quantity and depth, will give a detailed analysis of the materials through which the piles will be driven. Should insufficient boring information, i.e. lack of soil composition, gradation, density, and other characteristics, be provided the estimator takes on a substantial risk anticipating production.
Safety – Construction is inherently dangerous and pile driving is even more so. Fall protection, objects dropped from overhead, and unmarked utilities are just some of the considerations that must be addressed in a safety plan. The safety procedures set forth must be monitored and enforced to minimize the potential for injury on the site.
Scheduling – As piles are typically installed very early in the construction sequence on new construction, conflicts with proposed work typically isn’t a significant issue. When this work is performed as modification to existing structures, clearances for the equipment required to install this work must be examined in detail. A significant impact to this work will also be the relocation of existing overhead and underground utilities and the construction of new utilities in order to not impact the construction of these piles.
Ratios and Analysis
In that the plethora of variables regarding construction of CIP piles preclude any consistent ratios for labor / equipment / material / productivity, the best source of cross checking comes from the contractor’s own history.
This, of course, raises the chicken vs egg conundrum. To obtain production and cost data from one’s history, one must first construct the pile. To construct the pile, one must typically estimate the work. Without estimating and subsequently constructing the pile, history cannot be obtained.
To combat this, an outside consultant well versed in the work required, region the work will be performed, labor market available, equipment required, and other aspects will be the best source of confirmation of costs.
Additionally, searching through public agencies, published unit prices for contracts can be a valuable source of pricing confirmation. Typically, these public agencies will publish the unit prices provided by all bidders at some point.
Some agencies publish almost immediately after bid opening while some publish only after award of the project. Searching through the databases of unit prices for the similar work in the similar conditions will be a valuable guide to the estimator, provided due diligence regarding the pricing is performed.
Miscellaneous Pertinent Information
Test piles are the method with which a pile design would be confirmed on a project. That entails constructing a single pile per expected condition with the equipment, materials and methodology anticipated. This paper will not be addressing said operation; however, the estimator should be aware the costs for these piles are markedly more than that for the production pile.
As witnessed by recent events, volatility of material costs can significantly impact the price of the installed pile. From labor shortages due to pandemics or raw material availability due to global instability, the estimator must be aware of these cost impacts and do their best to incorporate those costs.
Dependent upon quantity, procuring the pipe pile material may be limited to timeframes known as “mill rollings”. Typically, the length and quantity of piles required would need custom fabrication which happens at certain times as decided upon by the manufacturers. This will have potentially substantial impacts to the schedule should the mill rolling not be conducive to meeting schedule requirements.
Steel Pipe Piles are manufactured at steel processing plants. These are limited in number and as such their location can impact costs directly. Should the plant and the project to which the piles are to be shipped be located on viable waterways, piles in excess of 100 feet in length could be barged to the project location. Should over the road travel be dictated, over length, overweight, and travel periods can impact delivery dates, times, and costs.
Additionally, should over the road transport be required, the length of pile to be transported will impact costs. Over length or overweight permits as well as additional splicing will add costs and the relevant conditions must be analyzed to achieve the most economical outcome.
Pay quantity for this type of item constructed under the presumed specification is to the nearest rounded whole foot per unit installed. Pay quantity is the length of pile that would be included in the calculation for compensation of the work. Some agencies will not pay for piles above grade yet are required for connection into the footing above while others will pay for all footage driven and cut off, whether incorporated into the structure or not. The calculations take these criteria into consideration.
Details and Plans
Pile Detail
Plan and Elevation of Wall 1
Footing and Pile Plan Wall 1
Plan and Elevation Wall 2
Footing and Pile Plan Wall 2
Wall Sections and Pile Elevations
Takeoffs and Pricing
Cast in Place Concrete Filled Pipe Pile
Glossary
Bedrock – A solid rock layer in the ground either at or below the surface.
CRSI – Concrete Reinforcing Steel Institute.
Capacity, Design – Design load that would be placed upon a pile. Capacity, Maximum – The highest load a pile would be able to support without failure.
Load – The amount of weight, either in tons or pounds, that would be placed upon a pile either in a temporary or permanent condition
Mill Rolling – Timeframe in which a steel mill will produce a specific type and size of pile.
Pile Hammer – A device with which piles can be driven into the ground. Many different hammers are able to be used in this work. Vibratory, Diesel and Air driven are the most common types.
Order Length – The length of pile to be actually fabricated to be installed based upon information gathered from the construction of a Test Pile.
Pay Quantity – Contractual establishment of method of calculation for compensation of an item of work. This will determine whether payment will be made for a portion of the pile installed or if all of the pile, including cut off portions, will be included for payment.
Pile Leads – Lattice type steel support frame that holds the pile in place and provides a track upon which the pile hammer would glide while driving the pile into the ground.
Pile, Production – Piles installed utilizing information obtained from the test pile install process such as maximum force of hammer, expected travel of ram, weight of ram and blows per foot.
Pile, Test – Piles installed under the conditions the piles are expected to be installed while under monitoring the process to ensure steel strength is not exceeded and design capacity is reached by achieving a particular depth in order to achieve design bearing.
Pile Splice – Joining sections of steel pile as needed to achieve the required total pile length for anticipated installation.
Pile Tip – Elevation at which the end of the pile embedded in the substrate rests.
Pile Top – Design elevation of the exposed end of the pile after driving.
Pile Type, Batter – Pile installed intentionally on an angle to the foundation surface not 90 degrees. This is used to combat overturning or sliding forces amongst other purposes.
Pile Type, Vertical – Piles installed vertically at a 90-degree angle
to the foundation surface.
Rebar – Steel bar used to provide strength to concrete as well as form of connection between the pile and foundation of the structure it will support.
Rigging – Materials with which a pile hammer is lifted in the air with a crane or excavator.
Soil Boring – Sampling of soil at various depths in a potential location of a structure where soil types, soil gradation, soil density, groundwater elevation, potential bedrock elevation, and other impactful characteristics to the subgrade soil conditions.
References
- New Jersey Prevailing Wage Determination, expiring February 28, 2023 for Laborers, April 30, 2023 for Dockbuilders and June 3, 2023 for Operating Engineers
- US Army Corps of Engineers document EP1110, dated 2020
- CRSI Standard Hook Details and ASTM Standard Reinforcing Bars
- Manitowoc 777 Crane Product Guide (including lifting charts)
- ICE HIH IP2 Product Guide
About the Author
Roy Huemer, CPE, has been immersed in the construction industry since the late 1970s. His diverse experience spans home construction, mechanical drafting, CAD, civil design engineering, and heavy highway construction, shaping a robust educational and professional journey.
Roy has held key roles, including Takeoff Technician, Field Engineer, Project Engineer, Estimator, Project Manager, Chief Estimator, Department Manager, and currently serves as a Private Consultant as well as Trainer of HCSS HeavyBid® and HeavyJob®.
A published author in ASPE’s Estimating Today, Roy has developed many training courses for ASPE and his own educational company. He’s an active member of ASPE’s National Education Committee, and collaborates with estimators and project managers across various industries, delivering expertise and guidance.
