LEA Advisory #45 Attachments—Methodology for Determining Remaining Landfill Capacity

Table 1: Comparison of Recommended Methods for Determining Remaining Capacity

Method	Cost	Accuracy	Type of Landfill	Size of Landfill	Equipment/ Expertise Required
Aerial Surveys with Computer-assisted Calculations	Generally highest cost, though may be less expensive than ground surveys for larger (over 10 acres) landfills.	Highest level of accuracy, with built-in cross checks. Should be accurate to within 10%.	All types of area landfills.	Appropriate for landfills over 10 acres.	Airplane, photogrammetry equipment, stereo plotter, autocad with add-on; operators for all of this equipment.
Ground Surveys with Manual Calculations	Middle cost; cost is generally less than aerial surveys for sites under 10 acres.	Depending on expertise and care of surveyors, map-makers, and whoever performs calculations, 10-20% accuracy.	Appropriate for all area-type landfills.	Best for landfills under 10 acres, or for larger landfills if it can be accomplished in-house at lower cost.	Manual surveying equipment, drafting equipment, planimeter or grid paper, calculator or computer spreadsheet; operators for all of this equipment.
Weight-Based	Low cost, particularly after first use of this method.	Accuracy of 20-25 percent is possible.	Appropriate for area-type landfills.	Appropriate for smaller and low-volume landfills.	Calculator or computer spreadsheet, accurate records of incoming material in volume or weight; care in performing calculations.
Trench Volume	Very low cost.	Accurate to within five percent.	Trench-type landfills with consistent trench dimensions, and area-type landfills with consistent cell dimensions.	Any size.	Calculator or computer spreadsheet; ability to perform basic geometric calculations.

* Table 1 is reproduced from the report entitled Determining Remaining Permitted Capacity of California’s Sanitary Landfills (Table 2, page 15)

Attachment B-1

The example calculations below demonstrate how remaining capacity may be determined from a topographical map. This form of calculation is commonly referred to as the "average end method." That is because you calculate the area of two end sections and determine the volume between them. The distance between the end sections can vary depending on the size of the landfill or the need for accuracy. Generally, 100-foot cross sections are used; however, decreasing the distance to 50 feet between sections can increase the accuracy of the calculations.

In Attachment B-2, a plan view of a typical landfill is shown. The darkened area of the plan view represents the footprint of the currently filled area and the lighter area represent the footprint of the total permitted area that is yet to be filled. An additional view of the landfill is displayed in the 3-D view located to the right of the plan view. Note that corresponding cross sections for the landfill are shown for both the plan and 3-D views. The distance between the two cross sections is indicated as 100 feet. This dimension was chosen as an example only and can be shortened or enlarged as needed or as calculations necessitate. As the size of a landfill varies, so will the number of cross sections necessary to determine the remaining capacity.

Cross sections A-A' and B-B' are displayed on the lower part of the page. The darkened area of the cross sections reflect the currently filled area and the lighter shaded areas indicate the area remaining to be filled. Note that on cross section A-A' the total permitted area of 18,000 sq ft includes the 12,000 sq ft of currently filled area; therefore, only 6,000 sq ft is available for filling. Likewise the total permitted area of cross section B-B' includes the filled area of B-B'.

Attachment B-2

Attachment B-3

3a. Total Permitted Volume - Currently Filled Volume = Remaining Volume (Capacity)

Methodology for Determining Remaining Landfill Capacity

Attachment A

Attachment B-1

Attachment B-2

Attachment B-3