Calculating Consequence Scores

Critical factors that are unchecked in the criticality calculator are ignored when scoring the pipe.

Critical factors are assessed as follows:

Critical factor	Individual criticality rating
Surface water pollution risk Property flooding risk Odour/Nuisance risk Ground water pollution risk Repair cost risk Traffic risk score Rail/Business disruption risk	Consequence rating determined from values entered manually in pipe data fields. Note that Repair cost risk and Traffic risk score may be calculated automatically (see SRM rating calculations section below)
Under building	Consequence rating of 5 is assumed for pipes with Under building field checked.
Access restrictions	Consequence rating of 3 is assumed for pipes with value set in the Access restrictions field.

The Consequence Calculator may be used to automatically calculate Repair cost factor, Repair cost risk and Traffic risk score values for each pipe. The values are calculated based on pipe category according to tables in the SRM Procedure.

Check the options in the SRM Rating group of the consequence calculator to automatically calculate pipe values.

Calculating repair cost risk and repair cost factor

A repair cost risk and repair cost factor may be calculated based on pipe properties and ground type. The repair cost factor may then be used in conjunction with traffic data to calculate a traffic delay consequence rating.

Repair cost risk and repair cost factor values are calculated based on pipe depth, pipe material, pipe size and ground type, where:

• Pipe depth is determined from the average of US depth from cover and DS depth from cover values, (if only one value is specified, the single value will be used)
• Pipe material is assumed to be brick if either US pipe material or DS pipe material field set to BR (Brick)
• Pipe size is determined from the larger of the values in the US width and DS width fields
• Ground type is determined from the Ground type field

The Repair cost factor and Repair cost risk pipe fields will be updated with the cost factor and cost risk values according to the following tables. Field values will be set to zero for pipes that do not have adequate data to determine a value.

 

Depth (m)	1.0 - 1.99	2.0 -2.99	3.0 -3.99	4.0 - 4.99	5.0 - 5.99	6.0 +
Repair Cost Factor Good ground	1.0	2.0	3.0	4.0	5.5	7.0
Repair Cost Factor Bad ground	1.5	2.0	3.5	5.0	6.5	8.5
SRM Category	C		B		A
Repair Cost Risk	1		3		5

Pipes up to and including 900 mm diameter

 

Depth (m)	1.0 - 1.99	2.0 -2.99	3.0 -3.99	4.0 - 4.99	5.0 - 5.99	6.0 +
Repair Cost Factor Good ground	4.0	7.0	13.0	19.0	26.0	33.0
Repair Cost Factor Bad ground	5.5	9.0	16.0	24.0	31.0	40.0
SRM Category	B	A
Repair Cost Risk	3	5

Pipes with more than 900 mm diameter and all brick sewers

 

Major sewers are assigned a minimum Repair cost risk according to the following:

Pipe properties	SRM Category	Repair Cost Risk
Combined/storm sewers > 1500 mm diameter	A	5
Foul sewers > 600 mm diameter	A	5
Combined/storm sewers > 600 mm diameter but less than 1500 mm diameter (inclusive)	B	3
Foul sewers > 450 mm diameter but less than 600 mm diameter (inclusive)	B	3

Calculating traffic delay risk score

The value in the Traffic level field and the setting of the Traffic divertable field are used in conjunction with the Repair cost factor (RCF) to determine a Traffic risk score, calculated based on the road traffic delay overall cost model in the SRM Procedure.

Repair cost factor may be manually specified or calculated automatically by the consequence calculator (see above).

An overall cost factor is calculated as follows:

Traffic flow (vehicles/day)	Roads without adequate diversion	Roads with adequate diversion
5,000 - 7,499	4.8 x RCF	1.6 x RCF
7,500 - 9,999	6.3 x RCF	1.9 x RCF
10,000 - 12,499	7.8 x RCF	2.1 x RCF
12,500 - 14,999	9.3 x RCF	2.4 x RCF
15,000 - 17,499	10.8 x RCF	2.6 x RCF
17,500 - 19,999	12.3 x RCF	2.9 x RCF
20,000 +	13.8 x RCF	3.1 x RCF

Overall cost factors (OCF)

 

A traffic risk score is then determined:

Overall cost factors (OCF)	0 -2.9	3.0 - 5.9	6.0 +
SRM Category	C	B	A
Traffic risk score	1	3	5

Overall cost categories

Critical factors that are unchecked in the criticality calculator are ignored when scoring the pipe.

Critical factors are determined as follows:

Critical factor	Individual criticality rating
Disruption risk	Consequence rating determined from value entered in pipe Disruption risk field.
Under building	Consequence rating of 5 is assumed for pipes with Under building field checked.
Access restrictions	Consequence rating of 3 is assumed for pipes with a value set in the Access restrictions field.

Ratings are calculated based on the number of customers supplied by the pipe and the internal diameter of the pipe.

The criteria to be used to determine a consequence rating are defined in the Criticality matrix in the Consequence Calculator. The criteria in the calculator can be edited, rows may be deleted from the grid or further values added to the bottom of the grid.

The Criticality score field of the pipe is updated with the consequence score calculated from the Criticality matrix. If the Criticality score is greater than the consequence ratings determined from the Critical factors, the Criticality score will be the value with which the pipe Consequence score field will be updated.

Criticality matrix column	Description
Score	Consequence rating.
Occupancy	Number of customers supplied by the pipe. Calculated as the sum of the Occupancy values of Property objects associated with the pipe. If a property does not have an Occupancy specified, the Default occupancy value specified in the Consequence Calculator is used for that property.
Key Occupancy	Number of key customers supplied by the pipe. Calculated as the sum of the Occupancy (Key) values of Property objects associated with the pipe. If a property does not have an Occupancy (Key) specified, the Default key occupancy value specified in the Consequence Calculator is used for that property.
Internal Diameter	Diameter of the pipe taken from value specified in Internal diameter field of pipe.