Calculating Debris Removal
Debris removal calculations can vary widely if proper methods for computing how much quantity will be removed. FEMA and other state agencies can require initial estimates of debris to be removed or award this type of project under a time and material contract agreement. However, calculating debris removal can be assessed using three common methods:
- Ground Measurement
- Aerial Photos
- Computer Models
Debris Removal: Ground Measurements
The first and preferred method of estimating debris removal quantities is performing ground measurements. Calculating debris removal using ground measurement must be completed following these recommendations:
- Define the area that is covered by the debris. Be specific and set your boundaries clearly.
- Differentiate between debris types and amounts. These quantities might be influenced by land use, grading and location.
- Divide the area into sections and classified them by debris classification, i.e. vegetative, buildings, metals, among others.
- Select an appropriate method to measure the area. You can perform representative samples or measure the entire area for example by blocks, or by elevation.
- Determine the equipment that will be used to complete the estimate, including surveyors, photos, tapes, roll-off wheel, and lasers.
- Determine and select the team that will be completing the debris removal estimate.
- Determine if debris removal activities will include personal property, such as furnishings, clothing, or related indoor equipment.
- Take a part all electronic devices and other harmful debris components, such as tires and oil storage containers.
- Recognized that some debris can undergo changes in volume during the handling process. For example soils could account for larger volumes when removed and vegetative debris could reduce its volume after being loaded into dump trucks.
- One acre of debris 10 feet high converts to 16,133 CY.
Debris Removal: Aerial Estimates
The second method available for estimating debris removal is the aerial measurement. Aerial estimates of debris removal could be used in areas where access is blocked, remote locations or large areas. It is also recommended to complete quick or emergency estimates by assuming or extrapolation of debris information gathered by ground crews. However, it might produce inaccurate values of volumes because it will be based on aerial photos, or satellite images that might not represent the best data of the impacted area. If the aerial measurement will be used to estimate debris removal, you can follow these recommendations:
- Compare before and after aerial photos of the disaster area.
- If available, compare several photos taken at different angles.
- Select a reference object with known dimension that will be used as the scale comparative to perform dimensional measurements.
- Consider a nominal value of uncertainty based on previous experience to account for areas not visible to aerial photography.
- Remember that some debris can undergo changes in volume during the handling process. For example soils could account for larger volumes when removed and vegetative debris could reduce its volume after being loaded into dump trucks.
Debris Removal: Computer Models
Recent technological advances can also be useful when completing estimates of debris removal. Computer models such as