Guidelines for Establishing Transfer Stations for Municipal Solid Waste
Section 3: Design Guidelines
Solid waste quantities anticipated at a transfer station should be based on estimates for the area to be served. These estimates are normally contained in the Regional Solid Waste Management Plan. These estimates are usually given in tonnes per year. Since a transfer station is concerned with the volume of waste that must be received, held, and transported, the estimated annual tonnage should be converted to cubic metres. Where local density information is not available, a conversion factor of 150 kg/m3 may be used for standard, uncompacted municipal refuse. Compacted refuse may have a density of 2 to 4 times greater, but waste discharged from a packer truck does tend to "spring back" and reduce its density again. For a station receiving about half of its waste from packer trucks, a density of about 200 kg/m3 may be assumed.
The annual tonnage or volume should be used as a basis to calculate the average daily quantity, based on the number of days that waste is received at the station. A peaking factor should then be applied, to convert the average daily quantity to a peak daily quantity. It is often useful to calculate an estimated peak weekly quantity as well, particularly for small stations, that may only haul waste weekly. Failure to provide for peak volumes may result in premature filling of the containers to the point of over-flowing, an unplanned for increase in haulage (and the associated costs) and unsightly conditions at the site.
Local conditions are very important in determining densities and peaking factors. For example, local building demolition activity can contribute high density wastes. The appropriate peaking factor can vary widely, depending on local waste stream components and population characteristics. Areas with large seasonal tourist populations or seasonal agricultural activities can have high peaking factors. For these reasons, average and peak quantities must be estimated in the context of local conditions, with reference to the Regional Solid Waste Management Plan.
A transfer station must provide sufficient volume, between one waste pickup and the next, to ensure that the bins or transfer trailer provided do not fill to overflowing. A direct dump station must provide sufficient tipping area to accommodate the numbers and types of vehicles arriving, their unloading times, and any waste sorting or processing that is to be done. Sufficient volume must be provided to accommodate peak waste periods, statutory holidays, and long weekends. Storage volume provided and pick-up frequency are essentially a trade-off. For a given population served (or waste generation rate), the larger the storage volume provided, the less frequent the waste pickups.
In some cases, acceptance of bulky goods such as appliances, auto hulks, furniture and wood wastes at transfer stations may provide the most convenient and practical method to the public for handling these types of wastes. Volume (space) provisions should be made for storing these wastes, if they are accepted at the site. Failure to provide bulky goods services may result in these items being placed in transfer station bins, resulting in inefficient use of bin space, premature filling of the bins to the point of over-flowing, more frequent hauling and an associated increase in operating and haulage costs. For transfer station sites in remote locations, the option of requiring the public to haul bulky items to a regional landfill site may be too onerous.
If bulky items are accepted at a transfer station site, they should be segregated to dedicated storage piles/containers. The piles, if kept properly clean of contaminants, could be allowed to build-up until economical loads are available for transport. The time period before economical loads are available for transport could be several months to several years.
Roads to a transfer station site and within the site should be designed to provide all season, all weather access. The minimum road width should be 8 metres. Designs must be in accordance with standard practice for the anticipated traffic volume and speeds. Sufficient space should be provided for queuing, such that vehicles need not stop on a public road or highway when entering the site. Traffic flow through the site should be considered. Gravelled surfaces may be acceptable, depending on the local context, but if dust or mud is a problem, asphalt paving should be provided.
Provision should be made to prevent stormwater and runoff from contacting waste. All waste containers should be leak-proof, or should provide for the collection of contaminated water and illegally dumped liquids. Tipping floors should provide drains and sumps to collect washdown water and illegally dumped liquids. Proper disposal of contaminated water should be ensured.
Transfer stations serving populations of 5,000 or more, or receiving 5,000 tonnes / year or more, should install weigh scales. Smaller stations should consider installing weigh scales or using an alternative (ministry approved) method of measuring waste quantities received, or instituting charges per vehicle or waste container, as a means of allowing the collection of tipping fees and thus of paying the costs of staffing and operating the station. The accuracy of specific scales or types of scales, for the purpose of charging fees, should be confirmed with the federal department of Consumer and Corporate Affairs - Weights and Measures.
Perimeter fencing, such as the chain link variety, is the first defence against wildlife intrusion. Bear-proof electric fencing has been used with success for both black bears and grizzly bears at several landfills in the province and should not represent a prohibitively expensive alternative for the small perimeters associated with most transfer stations. Electrifying the normal perimeter security fence may be feasible, with appropriate attention to warning humans of its presence, such as by using signs and other measures, and otherwise ensuring it is safe and user friendly. Careful attention must be paid to gate design, on the one hand to promote responsible use by humans (including both easy access and after use closure) while at the same time to prevent wildlife from entering the site.
Containers intended to receive organic waste should have lids, screens, or covers that will prevent access by bears and other predators, rodents, and birds. Alternatively, containers may be placed inside predator-proof enclosures that provide both easy access to users and promote closure after use (e.g., garage door type designs). Consideration should also be given to washing out containers between uses, either at the transfer station or at the landfill. Only sturdy, easily cleanable, animal-proof containers should be used. Buildings at direct dump facilities should be designed to minimize areas/spaces that afford a harbour for rats and other small mammals, and to be predator-proof. The importance of predator-proof containers cannot be over-emphasized as this design feature will prevent rewarding wildlife with a food source in the event that the exterior fencing is breached (e.g., by a gate left open, etc.).
Fencing should be provided around the perimeter of the site, with a lockable gate at any entrance point. The type of fencing may vary with the natural site features.
Transfer stations should be provided with a sign (or signs) posted prominently at the entrance, that contains the following information:
- facility name
- owner / operator with phone number and address
- emergency phone numbers for fire, police and medical assistance
- hours of operation (if applicable)
- prohibited materials
- materials accepted for recycling
- tipping fee schedule (if applicable)
- the presence of an electric fence (if applicable)
If recyclables are not accepted at the station, a sign should indicate the location of the nearest facility that does accept them. In addition, the sign should indicate locations, if known/available, where prohibited materials such as paint, used oil, lead-acid batteries and other items can be safely taken.
For facilities with buildings, employing staff during operating hours, water for fire protection should be provided in accordance with the Water Supply for Public Fire Protection — A Guide to Recommended Practice, as available through the Insurers Advisory Organization. For these larger stations, washdown water should also be provided.
A transfer station is an ideal location to provide bins for the dropoff of reusable and recyclable materials. Similar design considerations apply as for waste; the station should provide sufficient storage space, weigh scales and fire protection for larger stations, and signs giving users appropriate instructions. The dropoff of organic materials for composting requires that the bins be emptied frequently, depending on the type of material. Yard waste containing a significant amount of grass should be picked up daily, unless it can be shown that odours are not a problem at either the transfer station or the composting site. Yard waste consisting mainly of brush and leaves may be picked up weekly. Food wastes should be picked up daily.
At some rural transfer stations, waste oil receptors and lead-acid battery bins (with alkali material placed in the bottom to neutralize spilled acids) have been provided. This allows the public a convenient method of disposing of these materials which might otherwise be put into the transfer station bins.
In cases where recycling facilities are not located at the transfer station, a sign should be provided directing patrons to the nearest available facility.
Most transfer stations involve the dropping or pushing of waste down into a bin or trailer. It is important that safety features such as guard rails be incorporated to prevent people from falling into a bin, and stop logs or bars to prevent vehicle accidents. Transfer buildings should be designed with sufficient ceiling clearance to accommodate the vehicles that may enter and dump. It is desirable that transfer buildings have clear spans, without central columns to impede traffic.