David Langley is a retired engineer who has studied the proposal to construct a treatment plant in the Saanich East – North Oak Bay (SENOB) catchment area, probably at Haro Woods. The following is his presentation to the Core Area Liquid Waste Management Committee, delivered Aug 12, 2009:
Why is a plant needed in Saanich East – North Oak Bay?
The latest CRD Wastewater Update Newsletter (July/August 2009) provides five reasons supporting the need for this proposed facility. More information is now available through the extensive CRD documentation of reports and discussion reports that relates to the SENOB plant as part of the regional wastewater treatment system. My observations regarding the five stated reasons are as follows:
The size of the downstream central plant can be reduced.
- True, but what are the treatment cost implications? A graphic provided in a CRD PowerPoint presentation in April 2009 showed that smaller plants such as SENOB have substantially higher unit treatment costs than larger central plants.
- In this situation, at typical cost rates, the extra capital costs at the central plant to provide additional treatment capacity without the SENOB plant would be little more than half the SENOB capital costs
- The Macaulay/McLoughlin treatment plant capital costs may well be higher than typical. On August 26, the report on the best balance between future capacity and cost provisions at the Macaulay/McLoughlin treatment plant and the South Colwood plant will be coming to committee. The combined treatment plant cost rates at these two locations ($ per 1000m3/day) can then be compared with the SENOB cost rates
- If the SENOB plant is implemented, the sludge from this plant will be transferred to the central plant for treatment. What are the cost implications of this double treatment process?
Local opportunities will be created for heat and energy recovery and reuse
- Such opportunities would also be available in other areas of the region
- Potential buyers and revenues are very uncertain
- The Peer Review Group strongly recommended the exclusion of resource recovery and revenue considerations in the determination of the best overall treatment system
Capacity can be freed to handle a greater proportion of wet weather flows
- The SENOB catchment area has the lowest wet weather flow infiltration rates in the region
- At the critical wet weather management plant, Clover Point, the removal of the SENOB flows would reduce total flows by about 12%, not sufficient to avoid the proposed Stage 1 investment of $141 million in that location (CRD Discussion Paper 035-2)
The plant will increase future flexibility when planning for population increases
- According to CRD documentation of population projections for the whole sewage treatment area (038-DP-1) the potential SENOB area growth over 50 years is 33%. The estimated increase over 50 years in sewage flows to be treated is less than 10%
- The SENOB plant would serve a self-contained low-growth area (representing only 6% of the 50 year population growth in the whole treatment area) Its “flexibility” contribution to the rest of the regional system where 94% of the growth is taking place would be virtually zero
Attenuation tanks and upgrades to the trunk sewer will not be required.
- CRD have identified $45 million as these costs under the current waste management plan set in place several years ago. Long term requirements are for three tanks
- Only one tank is required in the Stage 1 time period.
- These earlier requirements, without a SENOB plant, should be reassessed in the light of all the new data and information available.
Summary
The progression from a “Centralized” to a “Distributed” to a “Flexible” regional treatment system has made the inclusion of a SENOB plant look more and more attractive. These are only words of comfort for the decision makers, with little regard to the facts.
The evidence to date shows that implementing a SENOB plant would increase total regional costs (where is the proper analysis of the “Least Cost Option”?) It would do nothing to support a flexible response to future regional growth patterns.
The August 26 report on Options 1 a) b) c) will provide the information to look again at the “with and without” SENOB scenarios in terms of total regional costs in conjunction with the two other plants.