Lesson 6: Solid Waste Collection

TIME IS MONEY!!

• To determine:
  • Capacity of vehicle
  • # of vehicles required
  • Crew size
  • Labor required

   

• Look at: (divide collection into specific tasks)

• Time required to put trash into the vehicle (pick-up time)
• Time required to drive between containers (c) or generation locations (l) (dbc or dbl)
• Time required to drive to and from the disposal site (haul time)
• Time spent at the disposal site unloading trash (at-site time)
• Amount of non-productive time (off-route time)
• Container capacity, waste vol

Used in both HCS and SCS analyses

Pick up time, P

• P_HCS(conventional)- time spent manipulating the container(s) at one waste generation site and driving to the next generation site
• P_HCS(swap/exchange)-time spent manipulating the container(s) at one waste generation site
• P_SCS - time spent on the designated service zone from time vehicle stops for first container till last container is loaded (same for manual and mechanical loading systems).
• Note: the pickup time may be further subdivided into
  • pc - the time required to pick up the waste container (may include dumping trash into vehicle)
  • uc - the time required to replace (unload) the waste container
  • zc - any special waste container handling time required

Haul time, h

• HCS, h= time spent driving between waste generation and disposal site
• SCS, h= time spent driving between waste generation and disposal site
• May be expressed as a one-way or a round trip time
• Does not include time spent at disposal site

To/From Dispatch Time, t₁ & t₂

• Time required to drive from dispatch to the first site at the start of the work day (t₁)
• Time required to drive from disposal site to dispatch at the end of the work day (t₂)
• Note: if the disposal and the dispatch site are the same thing, then t₁ & t₂ are essentially identical to the haul time (h)

At-site time, s

• Time spent at disposal site or transfer station

Round trip time, T

• Average time required to make one round trip to and from the disposal site
• Includes P_{(HCS or SCS)}, s, and h [ T=P + s+ (1or 2)h ]

Length of work day, H

• Amount of labor paid for (in hours or minutes) on a daily basis

Off-route time, W

• Non-productive time (fraction of work day)
• Necessary
  • check in/out
  • lost to traffic congestion
  • equip repairs, maint, etc.
• Unnecessary
  • excessive lunch time
  • unauthorized coffee breaks
  • talking
• W= (nonproductive time)/(total time)
• Range: 0.1-0.25 avg: 0.15
• Used to adjust H to the time available for work

Trips per day, N

• Number of times a vehicle can go out to collect waste per day
• HCS - same as the number of containers serviced
• SCS - the number of times the vehicle can go out to collect waste.  In an SCS system, the vehicle collects from multiple locations before returning to the disposal site.

Number of locations serviced per trip, L

• Used only in SCS systems
• Number of locations serviced before the vehicle returns to the disposal site.

Number of containers emptied per trip, C_t

• Similar to L above
• Used only in SCS systems
• Number of containers emptied before the vehicle returns to the disposal site.

Used primarily in SCS analyses to determine the maximum number of homes or containers a vehicle can service

Container volume, c - average volume of containers serviced

Container utilization factor, f - average portion of container containing garbage

Collection vehicle volume, v - volumetric capacity of collection vehicle

Compaction factor, r - factor which adjusts for the use of compactors within the packer trucks

Calculating the maximum number of containers a packer truck can service in one trip

C_t(max)= (v*r) / (c*f) = (effective vehicle volume) / (volume of waste in a container)