the weekend as is often the arrange- ment. Otherwise there should be some spare disposal capacity to avoid congestion at the weekend.
DISPOSAL CAPACITY
Disposal capacity is defined as the cubic capacity of the receptacles
dustbins or containers regularly filled and emptied in a given period. For comparison of schemes with different frequencies of collection this period is taken as a week. and the capacity is expressed in cubic feet per week. It has been found that the average disposal capacity per dwelling varies widely from scheme to scheme. In those examin- ed with dustbin disposal it ranged from 1 to 3 ft3 per dwelling per week; with communal container dis- posal from 23 to 8 ft3: and with chute disposal from 13 to 11 ft3. In many of the examples with high dis- posal capacity per dwelling this was the result of high frequency of col lection rather than of high re ceptacle capacity. It is necessary to consider each case individually to decide what is the most economical and otherwise suitable combination of these factors to achieve a par- ticular disposal capacity.
As a result of the user study it has been concluded that, with dust- bin and communal container SVS- tems, an average disposal capacity of 3 ft3 per dwelling is desirable for ordinary households. In the former case this may suitably be provided by means of one 34 ft3 British Standard dustbin (B.S. 792) per dwelling and one collection per
week. In the case of communal con- tainers, this disposal capacity re- quires, with once-weekly collection. ayd3 container per 8 dwellings. 14 yd3 container per 10 dwellings.
OI
а
This disposal capacity conforms with that suggested in the Code of Practice 1 ft3 per person-if it is assumed that dwellings, on the aver. age, house 3 persons. For dwellings with chutes, however. it appeared from the user study that a somewhat higher weekly disposal capacity would be desirable up to say 5 ft3 per dwelling. There may be various reasons for this difference, and the following factors are relevant;
(a) Conditions at the base of સ chute where some refuse arrives
132
with considerable force, tend to cause spillage before the con- tainer is full,
(b) It is not possible for users to pack and compress the refuse at the time of disposal as it is with dustbins and sometimes with communal containers, though at some schemes care- takers do this systematically.
(c) Tenants with communal con- tainer disposal tend more than those with chute disposal to keep refuse before disposal, and consequently can more often select their time for disposal; further, since a communal con- tainer is generally visible to the user while a container at the base of a chute is hidden, users in the former case are more likely to retain their refuse when they know the container is full and so ensure a more even output.
(d) Where weekly disposal capaci
ties are up to 5 ft3 per dwelling the proportion of dwellings with 2 or 3 collections per
week
is greater with
with chute systems than with communal containers. Consequently chutes are more liable to the difficulty of reduced disposal capacity at week-ends when output of re- fuse is highest.
In addition to adequate overall disposal capacity, it is desirable to provide for a degree of flexibility in refuse disposal systems. This is particularly important with chutes, where users are generally not aware of congestion at particular con- tainers. Flexibility is more easily achieved where replacement of full containers between collections is a normal part of the system. since means are then available for moving containers to those positions where they are most required. Provided such means lifting trolleys or wheels on containers-are supplied. flexibility ran sometimes be intro- duced merely by the interchange of containers between heavily and lightly loaded chutes; alternatively some spare containers
may be pro- vided.
Table 1
——
ESTIMATED CAPITAL COSTS
System
1. Single refuse container with lid, stand-
ing in open on concrete plinth
2. (a) Single container with lid in three- sided brick enclosure and concrete roof
(b) Two containers with lids, all as
2(a)
Estimated Number of
Capital cost
capital
cost
dwellings served
per
dwelling
£36
20
£1.8
£95
20
£4.75
£150
40
£3.75
3. (a) Two containers in brick enclosure, concrete roof, steps to hopper, screen walls, and steel roller shut- ters
£331
40
£8.25
£615
30
£7.7
(b) Four containers, all as 3 (a)
4. (a) Twin 15 in. diam. standard salt- glazed pipes as refuse chutes, two containers, chamber built on end of main staircase serving 8-storey blocks of flats
(b) As 4 (a) but constructed in a pro-
prietary system
in.
18 5. Single
diam spun concrete chute, two containers on wheels, chamber. Built free-standing in stair- well. Serving 10-storey block
6. Garchey system of refuse disposal, including sink receiver, main receiver tanks, pumps, ducts and incinerator house
Le
£775
40-24
£19.4
- £32.3
£930
40-24
£23.25-£38.8
£421
40-24 £10.5
-£17.5
£98 -£105
THE HONG KONG & FAR EAST BUILDER VOLUME 18, NUMBER 5