What do price excavation and backfill mean?

Backfill, in construction, is the activity of returning the soil and gravel that are removed during building construction or using them again to toughen and support the foundation of the building or any other structural component.

The cost of excavation = Total excavation by volume x Excavation cost per unit.

A usual residential excavation construction work runs around $5,000 and many companies demand from $40 to $150 an hour. Project bids are created in accordance with the number of cubic yards of dirt transported, from $50 to $200 per cubic yard. Considering the standard cost of excavation and estimation depending on the size of the project and soil or gravel to be excavated is called pricing excavation.

Nowadays, in the construction industry, the excavation trade is typically carried out by contractors who are experts at this job. Excavation contractors are more experienced who concentrate on a certain single type of construction. Many subcontractors do backfill work by using excavators.

Excavation equipment

The transportation cost of minor items like plate compactors, rollers, bobcats, and small tractors to and from the construction site is priced on the ‘General Expense Sheet’ below “Trucking and Material Handling.” Transportation of major instruments like backhoes, bulldozers, road rollers for leveling, loaders, power shovels, and so on are priced better on one-to-one equipment basis considering the loading, unloading, truck expenses as well as any rental charges. All these item prices cover the cost of trucking, related to carrying some subsidiary construction goods and equipment where the supplier does not dispatch them to the site.

Types of excavation methods in general building construction

Site cut-and-fill operations

Expansive operations require large-sized, earth-transferring scrapers and bulldozers usually working in teams to excavate and deposit huge amounts of material, which is then leveled and compacted by another team of rollers, water trucks, and graders.

Basement-type excavations

To excavate the basements, a track backhoe between 0.5 to 1 cubic yards quantity is necessary. For massive basements, one or more than one track loaders of 2 to 3 cubic yard quantity are used to excavate and dig the pit but this may not be cost-effective.

Trench excavations

Smaller trenches for shallow pipes and cables are dug by trenching machines but for the larger trenches, backhoes are essential. Large backhoes are required to excavate deep trenches, and generally, they place the excavated material on either side of the trench, where it remains until obtained for backfilling. The backfill material is then transferred back to the site when it is used.

Pit and sump excavations

To excavate by pit and sump method, backhoes are required. A particular size of a backhoe is used and it depends on the hole size to excavate from the trench. Many tiny pits over the site area are dug and the backhoe is mounted on rubber-tired tractors as they have greater maneuverability over track-mounted machines.

Hand excavation

It is more economical to use the correct piece of equipment to excavate rather than to perform by hand. In certain rare situations, hand excavation is more efficient than the use of machinery. Also, for trimming edges of the trench, small backhoes are useful for precision.

Excavation productivity

It depends on the following aspects:

Job factors

1. Type of material to be backfilled or excavated.
2. Moisture condition of materials.
3. Expected Weather conditions and calamities.
4. Access to the construction site.
5. Availability of gravels and fill materials.
6. Wage and price levels at the work location.

Labor and management factors

1. Quality of job supervision, contracting work, and labor.
2. Types and quality of tools and equipment.
3. Experience and records of previous projects.

Type of material to be backfilled or excavated

Various soils, gravel, and rocks can give variants in the productivity rates but may be tedious to locate the quality and nature, to excavate the materials. Even when soil reports are available, the information they contain may be incorrect as the data produced from the sampling procedures may contain approximate results. Thus, detailed reports during site investigation provide accessibility to reliable soil reports. The proof of soil reports must be carefully and deeply discussed to estimate efficiently.

Moisture conditions of materials

Wet substances are heavier than dry substances, thus, the removal rate of debris may reduce when a substance is wet. In clayey soil, moisture leads to slippery surroundings that slow the work progress. Also, some soils can be sticky in wet circumstances that too reduces productivity.

If the addition of water to soil is regulated so that it does not get too sticky like clay soil or too much dried up like a dry backfill, maintaining the optimum moisture content in the soil, then removal of soil can become faster and easier.

Expected weather conditions and calamities

The weather conditions are sometimes unpredictable, especially the soil erosion (topsoil is washed away) during heavy rain pours. The unit cost used in the estimate relies on the assumption that the weather will be suitable. Hence, necessary measures must be taken before the demolition of the site area.

Access to the construction site

Productivity may be reduced when the vicinity of the site is in a congested area forcing the excavator to work around the other site activities. Thus, to estimate the conditions on site and adjust the cost, the estimator must predict the same.

Productivity rates

If contractors do not have the productivity records, various contractors refer to Building Construction Cost Data that give crew productivity rates data. For instance, the productivity of hydraulic excavators can be taken from information published by Caterpillar, Inc. But, it is advisable to maintain the records by the contractor since they give better productivity rates.

Excavation materials

Materials in the excavation and backfill work contain gravel to meet the designer’s specifications to backfill the area. Material prices for backfill have two elements, the price of providing material to the site and the price of scattering and compacting the material. To estimate the ‘supply cost’ of these substances is the job of the estimator. To estimate the materials that are in-ground and compacted, the estimator does it separately for cost-effectiveness and clearing. To backfill or excavate the basement, the excavator leaves behind enough material before transferring to dump trucks next to the basement area to use the backfill material around the completed basement.

Calculating trucking requirements

To estimate the optimum number of trucks required to transfer soil and gravel, an equation is used,

$Number of Trucks Required=\frac{Unloading Time}{Loading Time}+1$

Most excavation companies and estimators prefer to have more rather than less capacity so that the excavator is kept busy.

Context and Applications

• Bachelors in Technology (Civil Engineering)
• Masters in Science (Geotechnical Engineering)
• Masters in Science (Soil Mechanics)  

Practice Problems

1. Which of the following statements is correct?

1. The proof of soil reports must be carefully and deeply discussed to estimate efficiently by the estimator for assessing soil and gravel conditions.
2. The gravel material can be used for backfilling.
3. Excavation trade is typically carried out by contractors.
4. All of these

Correct option- d

Explanation: The proof of soil reports must be carefully and deeply discussed for the estimator to estimate the soil and gravel conditions. The gravel material can be used for backfilling and the excavation trade is typically carried out by contractors. All the statements are correct.

2. How much do the companies usually demand for excavation?

1. $40 to $150 an hour
2. $50 to $160 an hour
3. $60 to $170 an hour
4. None of these

Correct option- a

Explanation: The expense that companies demand for excavation is between $40 to $150 an hour.

3. Which one of the following is a type of excavation?

1. Excavator method
2. Basement type excavations
3. Boulder’s method
4. Backhoe loader method

Correct option- b

Explanation: The type of excavation is basement-type excavations.

4. What is the cost per day of a 0.5CY wheel backhoe?

1. $375
2. $380
3. $385
4. $390

Correct option- c

Explanation: The cost per day of a 0.5CY Wheel backhoe is $385.

5. Which excavation is normally used for shallow pipes?

1. Trench excavations
2. Pit and sump excavations
3. Site cut-and-fill operations
4. Hand excavations

Correct option- a

Explanation: The excavation normally used for shallow pipes is the trench excavations.

Related Concepts

• Proper slope and drainage of soil due to erosion
• To estimate the unit cost compatible for homeowners
• Cable-operated excavator