Changes

Assumptions for the above costs and the following table below are based on the following:

Assumptions for the above costs and the following table below are based on the following:

*For rainwater cisterns it is assumed that no rehabilitation work will be needed to maintain acceptable storage and drainage performance over a 50 year period of operation (40 for plastic cisterns), given that pretreatment devices are in place and are being adequately maintained. The annual average maintenance cost value represents an average of routine maintenance tasks, as outlined in Table 7.28. All cost value estimates represent the NPV as the calculation takes into account average annual interest (2%) and discount (3%) rates over the evaluation time periods.

*For rainwater cisterns it is assumed that no rehabilitation work will be needed to maintain acceptable storage and drainage performance over a 50 year period of operation (40 for plastic cisterns), given that pretreatment devices are in place and are being adequately maintained. The annual average maintenance cost value represents an average of routine maintenance tasks, as outlined in Rainwater Harvesting: Key Components, Descriptions and Routine I&M Requirements table above. All cost value estimates represent the NPV as the calculation takes into account average annual interest (2%) and discount (3%) rates over the evaluation time periods.

*Life cycle cost estimates have been generated for two design variations that can be used year-round: underground concrete cistern; and indoor plastic cistern systems. For each design variation, life cycle cost estimates have been calculated for two level-of-service scenarios: the minimum recommended frequency of inspection and maintenance tasks in the table below to provide an indication of the potential range. Only the indoor plastic cistern requires rehabilitation within the 50 year evaluation period. At year 40 it is assumed the plastic cistern is replaced with anew one.  

*For maintenance frequencies and requirements and the life span of each practice are based on both literature and practical experience. Life cycle and associated maintenance costs are evaluated over a 50 year timeframe, which is the typical period over which infrastructure decisions are made.

*For maintenance frequencies and requirements and the life span of each practice are based on both literature and practical experience. Life cycle and associated maintenance costs are evaluated over a 50 year timeframe, which is the typical period over which infrastructure decisions are made.

*For [[bioretention]], it is assumed that some rehabilitation (e.g., rehabilitative maintenance) work will be needed on the filter bed surface once the BMP reaches 25 and 50 years of age in order to maintain functional drainage performance at an acceptable level. Included in the rehabilitation costs are (de)mobilization costs, as equipment would not have been present on site. Design costs were not included in the rehabilitation as it was assumed that the original LID practice design would be used to inform this work. The annual average maintenance cost does not include rehabilitation costs and therefore represents an average of routine maintenance tasks, as outlined in the Table under section, [[Inspection and Maintenance: Bioretention & Dry Swales#Routine Maintenance - Key Components and I&M Tasks|Routine Maintenance - Key Components and I&M Tasks]] above. All cost value estimates represent the net present value (NPV) as the calculation takes into account average annual interest (2%) and discount (3%) rates over the evaluation time periods.

*For [[bioretention]], it is assumed that some rehabilitation (e.g., rehabilitative maintenance) work will be needed on the filter bed surface once the BMP reaches 25 and 50 years of age in order to maintain functional drainage performance at an acceptable level. Included in the rehabilitation costs are (de)mobilization costs, as equipment would not have been present on site. Design costs were not included in the rehabilitation as it was assumed that the original LID practice design would be used to inform this work. The annual average maintenance cost does not include rehabilitation costs and therefore represents an average of routine maintenance tasks, as outlined in the Table under section, [[Inspection and Maintenance: Bioretention & Dry Swales#Routine Maintenance - Key Components and I&M Tasks|Routine Maintenance - Key Components and I&M Tasks]] above. All cost value estimates represent the net present value (NPV) as the calculation takes into account average annual interest (2%) and discount (3%) rates over the evaluation time periods.