Section 6.4 of the HRS Guidance Manual
Tier C of the HRS is used when the volume of the source can be determined. Tier C cannot be used for the unallocated source.
The following may provide accounts of the source volume (i.e., capacity):
- PRP data
- State records
- Property records
- EPA signed and finalized compliance orders
- Aerial photographs.
To calculate the volume of the source, all of the following must be true:
- The volume of the source can be estimated.
- The hazardous constituent quantity and/or hazardous wastestream quantity were not adequately determined for the source.
If the volume of the source can be estimated:
- Evaluate the volume measure using the dimensions for the source type, specified in HRS Table 25.
This measure can be obtained by using the engineered capacity for certain source types (e.g., landfills) or the maximum volume for source types that are not specifically engineered (e.g., piles, quarries).
- Based on the volume, assign the source a value for volume using the appropriate Tier C equation found in HRS Table 25.
- Assign the source a value of 0 for the area measure (Tier D). Select the highest of the values assigned to the source (hazardous constituent quantity, hazardous wastestream quantity, and volume) as the source hazardous waste quantity value. (Do not round to the nearest integer.)
If the volume of the source cannot be determined:
- Assign the source a value of 0 for Tier C.
- Evaluate Tier D for this source.
TIPS AND REMINDERS
- Tier C is based on capacity, not the actual contents of the source (e.g., use the total drum volume, not the volume of the waste when deposited; use the surface impoundment oncefilled volume, not the volume of the waste disposed of in the impoundment).
- Use Tier C for containerized types (e.g., drums, tanks) and for source types with reasonably welldefined horizontal and vertical boundaries (e.g., waste piles).
- Subsurface source types generally need engineered drawings to support volume calculations (e.g., landfills, buried surface impoundments). Obtaining representative depth measurements of these source types during the SI is not recommended. Geophysical surveys generally should not be used to document source volume.
- Waste permit applications often include waste unit designs specifying volume capacity.
- Tier C is not applicable for unallocated sources.
- For a quarry, Tier C volume measures cannot be assumed to be equal to the volume of the filled quarry unless there is a reasonable basis for making that assumption. The scorer should attempt to estimate the level at which the waste accumulated in the quarry. For dry quarries or quarries where waste has migrated, the scorer should look for indicators of the previous maximum depth of wastes (such as contaminated waterlines). Volume may be calculated based on this depth. If the scorer cannot establish that waste was historically deposited to a certain depth, calculate hazardous waste quantity based on current conditions (i.e., using Tiers A, B, and D, as appropriate).