Practice Notes
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Approved for Publication 03.02.2005
Public Buildings Committee
Practice Note No 20
REVALUATION 2005
WASTE WATER TREATMENT WORKS
1.0 INTRODUCTION
This report Practice Note deals with the valuation of all Public Waste Water Treatment works, including Public Septic Tanks but does not apply to Effluent/Water Treatment facilities, which are “used or intended to be used mainly or exclusively in connection with services to the land or buildings”. (e.g. Effluent Treatment facilities within a Paper Mill.)
2.0 BASIS OF VALUATION
All treatment works are to be valued on the Contractor's Basis using costings appropriate for the tone date of 1st April 2003 having regard to Basic Principles Practice Note 2 and Public Buildings Practice Note 4, where appropriate.
3.0 CLASSIFICATION
Sewage Works have historically been classified in the following manner.
-
Biological Plant
-
with sludge thickening and sludge treatment
-
with sludge thickening but without sludge treatment
-
without sludge thickening or sludge treatment
-
-
Activated Sludge Plant
-
as A(i)
-
as A(ii)
-
as A(iii)
-
-
Extended Aeration Plant or Oxidation Ditch with no Primary Settlement
-
as A(i)
-
as A(ii)
-
as A(iii)
-
-
Primary Settlement only
4.0 METHOD OF VALUATION
In the absence of detailed information to allow a full Contractor's Basis valuation to be made for smaller Sewage Treatment Works serving populations up to 8,000 the following method should be adopted. A valuation may be carried out by reference to the table of rates based on a cost per head of optimum (design) capacity by Sewage Works type.
The unit cost rates to apply are which has been provided as an appendix to this note.
The rates shown cover all elements excluding Land value
Adjustments will require to be made for non - rateable items and guidance is provided below.
Works serving up to 1,000 population - an adjustment of 15% should be made for non rateable items.
Works serving between 1,001 and 4,500 - an adjustment of 17.5% should be made for non rateable items.
Works serving between 4,501 and 8,000 - an adjustment of 20% should be made for non rateable items.
Larger works serving over 8,000 population should be valued on the full Contractor's Basis and the table should not be used.
5.0 OVER-CAPACITY
Treatment works are generally built with a design capacity of at least three times the anticipated average Dry Weather Flow. (Dry weather flow is the daily flow into the works after a period of 7 days dry weather). No allowance needs to be made for this additional capacity as it is required to deal with seasonal fluctuations in flow.
If a treatment works serves an area where there is a local tourist industry which may produce different Dry Weather Flows at different times of the year the works will have been designed to be capable of dealing with the quantity of flow at peak holiday times. In comparison the flow at off peak times will be considerably reduced.
No over-capacity allowance should be given for tourist season fluctuations.
If, however, a Treatment works has been built with a capacity which reflects a projected population increase which has not been reached, and is not likely to be reached during the quinquennium, or for the treatment of a trade effluent process which may now have ceased, then it may be necessary to make an allowance.
The figure for "used capacity" is derived by taking the actual equivalent population as a percentage of the optimum design population.
The following allowances should be applied to all works, where appropriate
Over - Capacity Allowances
|
Used Capacity |
Percentage deduction |
|
80% or more |
NIL |
|
79%-75% |
5% |
|
74%-70% |
10% |
|
69%-65% |
15% |
|
64%-60% |
20% |
|
59%-55% |
25% |
|
54%-50% |
30% |
|
49%-45% |
35% |
|
44%-40% |
40% |
|
39%-35% |
45% |
|
34%-30% |
50% |
|
29%-25% |
52.50% |
|
24% or less |
55% |
6.0 AGE AND OBSOLESCENCE
Allowances should be applied in accordance with Basic Principles Practice Note 2 should be applied taking care to apply the appropriate allowance (Buildings), (Plant), (Civils) or (Tanks) allowance.
Please note that Concrete tanks e.g Storm or Settlement etc should be treated as Civils when considering any age and obsolescence allowance.
For those works serving populations up to 8,000, valued using the table of rates provided, a notional age and obsolescence should be applied having regard to the ratio of buildings: civils: tanks etc.
7.0 LAND VALUE
It should be borne in mind that the level of value adopted should reflect the assumption that the development of the site is confined to the class of subject under construction. The prevailing use value in the locality may be a useful indicator but care must be taken to ensure that any values attributable to say residential or commercial uses , for example, are discounted where appropriate.
The level of value applied to the site should be not be lower than agricultural value or higher than prevailing residential value for adjacent land.
8.0 DECAPITALISATION RATE
The appropriate statutory decapitalisation percentage should be applied
TABLE OF RATES PER HEAD OF POPULATION TO REPLACEMENT CAPITAL VALUE (EXCLUDING LAND)
| TYPE OF WORKS | |||||||||||
| OPTIMUM / DESIGN CAPACITY |
(A)(i) |
(A)(ii) |
(A)(iii) |
(B)(i) |
(B)(ii) | (B)(iii) |
(C)(i) |
(C)(ii) |
(C)(iii) |
(D) |
SEPTIC TANKS |
| 100 | £780 | £650 | £390 | £780 | £650 | £390 | £670 | £480 | £290 | £170 | £320 |
| 200 | £760 | £590 | £370 | £760 | £590 | £370 | £650 | £450 | £270 | £160 | £290 |
| 300 | £730 | £550 | £330 | £730 | £550 | £330 | £620 | £430 | £260 | £140 | £270 |
| 400 | £700 | £530 | £330 | £700 | £530 | £330 | £600 | £410 | £240 | £140 | £240 |
| 500 | £680 | £520 | £310 | £680 | £520 | £310 | £570 | £390 | £230 | £130 | £230 |
| 750 | £630 | £430 | £260 | £630 | £430 | £260 | £530 | £350 | £200 | £130 | £200 |
| 1000 | £570 | £410 | £240 | £570 | £410 | £240 | £480 | £310 | £160 | £120 | £160 |
| 1250 | £530 | £390 | £210 | £530 | £390 | £210 | £450 | £290 | £150 | £110 | £150 |
| 1500 | £510 | £370 | £200 | £510 | £370 | £200 | £420 | £270 | £130 | £110 | £130 |
| 1750 | £470 | £340 | £180 | £470 | £340 | £180 | £400 | £260 | £130 | £90 | £130 |
| 2000 | £440 | £310 | £170 | £440 | £310 | £170 | £370 | £240 | £120 | £80 | £120 |
| 2250 | £410 | £290 | £150 | £410 | £290 | £150 | £350 | £230 | £110 | ||
| 2500 | £400 | £290 | £140 | £400 | £290 | £140 | £350 | £220 | £110 | ||
| 2750 | £390 | £270 | £140 | £390 | £270 | £140 | £330 | £210 | £110 | ||
| 3000 | £370 | £260 | £140 | £370 | £260 | £140 | £310 | £200 | £110 | ||
| 3250 | £350 | £260 | £130 | £350 | £260 | £130 | £290 | £200 | £90 | ||
| 3500 | £350 | £250 | £110 | £350 | £250 | £110 | £280 | £190 | £90 | ||
| 3750 | £330 | £240 | £110 | £330 | £240 | £110 | £280 | £180 | £90 | ||
| 4000 | £330 | £240 | £110 | £330 | £240 | £110 | £270 | £170 | £90 | ||
| 4250 | £320 | £240 | £110 | £320 | £240 | £110 | £270 | £170 | £90 | ||
| 4500 | £310 | £240 | £110 | £310 | £240 | £110 | £260 | £170 | £90 | ||
| 4750 | £310 | £240 | £110 | £310 | £240 | £110 | £250 | £170 | £90 | ||
| 5000 | £290 | £240 | £110 | £290 | £240 | £110 | £240 | £170 | £90 | ||
| 8000 | £270 | £220 | £110 | £270 | £220 | £110 | £230 | £160 | £90 | ||
NOTE: Categories A - D require adjustment for non-rateable
items
up to 1,000 -15%
Between 1,001 and 4,500 - 17.5%
Between 4,501 and 8,000 - 20%
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