Wastewater System - Tavistock

The County maintains a diverse portfolio of assets that are required to provide the community of Tavistock with the safe collection and treatment of wastewater. The Tavistock wastewater sewage lagoon provides wastewater treatment for residential, commercial, industrial and institutional users in the Village of Tavistock.

The wastewater collection network transports waste to the lagoon for treatment. The wastewater collection network consists of a mix of gravity mains, low pressure mains and forcemains. Wastewater flows by gravity wherever possible, where changing elevations require the use of sewage pumping stations (SPS). Other specialized structures such as maintenance holes, valve vaults, meter stations, diversion structures and siphons are required to convey wastewater to the lagoon.

Inventory

The replacement cost valuation for the linear assets in this portfolio are based on current tender prices, where available. The replacement cost valuation for wastewater vertical is based on the latest information available, which includes current replacement costs, insurance valuations, inflation, and valuations from studies and assessments completed in prior years.

Data quality improvements have resulted in reductions to the sanitary mains as some assets were found to be storm mains or were not County owned assets and quantity updates were made to align with the County’s Geographical Information System ensuring more accurate and current information.

Condition

The percentage of assets in poor or critical condition has increased from 19% as reported in the 2024 AMP to 22%. The percentage of assets in good or excellent condition has decreased from 53% as reported in the 2024 AMP to 51%. As assets continue to age their condition rating will decline until lifecycle strategies are triggered and completed.

Key Performance

The wastewater network collects and treats wastewater from homes, businesses, institutions, and industry. Wastewater travels through the sanitary sewer system to the lagoon for treatment. It is intended that all wastewater assets will be maintained, rehabilitated, and replaced to perform the same function and manage the same capacity as they are currently designed to do. To ensure levels of service are maintained, staff monitor impacts from changes to capacity demands to plan for changes to current practices and budget requirements.

Proposed Levels of Service Review

Information on the scenarios reviewed is contained within the AMP document. As the system’s reserve balance and proposed funding under all scenarios are sufficient to fund the short-term lifecycle replacement needs, the average expected condition of the portfolio is the same under all scenarios for nearly 30 years, which aligns with the 2025 Budget Survey responses where 68% of respondents indicated that the service level related to municipal water and wastewater services in East Zorra-Tavistock should be maintained. The high overall risk under all scenarios is driven by the replacement cost and lifecycle needs related to the lagoon system in the long-term which can be mitigated using debenture funding if those assets are at risk of being unable to provide the required services.

Based on the analysis, staff are recommending Scenario D. The proposed level of service target is to fund the system at 60% of overall lifecycle needs. The use of PVC pipes for linear started becoming popular in the 1970’s; their useful life of 90 years is theoretical as this material has not been in use long enough to confirm the lifespan. Staff also identified an improvement area in 2024, to look at the lifecycle strategies for process assets as it may be beneficial in the long-term to incorporate various strategies and not anticipate a run-to-failure strategy on some of these assets. Once incorporated this may result in reductions to the annual investment required, as such staff feel it is not prudent to target the fully funded scenario at this time.

Funding Gap Analysis

Planned Investment Level
An estimated inflationary rate is not included in the planned investment in the table below as the 2025 investment level exceeds the proposed investment recommended.

Proposed Investment Change
As the 2025 investment level exceeds the proposed level identified, staff are proposing a reduction to the annual contribution to reserve of $250,000 for 2026, which results in a reduction in the monthly fixed charge for the average residential user of approximately $14.13 or $169.56 annually. The industry in Tavistock is currently undergoing changes that are anticipated to reduce the overall system revenue, thus resulting in a decrease to the contribution to the Wastewater – Tavistock reserve. Staff will continue to re-assess with each budget cycle to determine if further rate reductions can be achieved.

Comparison of required investment to proposed investment (millions)