On July 1, 2017, the Halifax Water enabled stormwater credits for the Site Related Flow charge for Non-Residential stormwater customers.
In order to qualify, non-residential customers must meet the eligibility requirements.
In order to qualify for the credit program, the private stormwater management system for the property must match the post-development peak flow rate with the pre-development peak flow rate for, at minimum, the 1:5 year storm event. This can be achieved utilizing a number of design components such as, but not limited to:
- Detention Ponds
- Detention Tanks
- In line pipe storage
- Roof Storage
- Engineered Wetlands and/or
- Green Infrastructure
A Non-Residential Customer that demonstrates their Site Related Flows are detained on their property or an adjacent property, as part of an overall stormwater management plan, is eligible to receive a credit. The initial stormwater credit application must be submitted and accompanied by a record drawing for the site specific stormwater management plan or site grading plan prepared and stamped by a professional engineer. The record drawing must include the calculations confirming the stormwater management system for the property either matches the post-development peak flow rate with the pre-development peak flow rate the 1:5 year storm event, or betters the post-development peak flow rate to a larger storm event. Record drawings prepared in support of a Building Permit Application process can be considered. The Building Permit Application process shall include information on the recommended maintenance and cleaning activities and the respective frequency.
The stormwater credit must be re-applied for annually using the Stormwater Credit Renewal Form and the application shall provide confirmation that the private stormwater management system was maintained and cleaned as per the recommendations of the professional engineer or the manufacturer’s recommendations. The certification can be provided by the person responsible for maintaining and managing the property or site.
In areas where combined stormwater and wastewater systems exist, a credit cannot be provided, as the detention achieved in these sewersheds may be used to create wastewater capacity for development.
Residential Customers that would like to apply for a credit and be billed as a Non-Residential Customer, must complete the initial stormwater credit application and submit all of the same documentation for review.
You are also required to reapply annually with the Stormwater Credit Renewal Form.
- Pervious asphalt promotes groundwater recharge and this area can be removed from the impervious area calculation. It cannot be used in obtaining a credit where its functionality is seasonal in nature. It shall be cleaned regularly to ensure it is functional. A Customer will be required to apply annually for this billing adjustment and provide certification that the pervious asphalt is functioning as designed.
- For properties sharing a private stormwater management system, Halifax Water may request letter(s) from the respective property owners outlining how the system operates and agreements that exist to enable the sharing of the system(s). Details on the design functionality of the system are to be supplied by an engineer.
- Halifax Water reserves the right to audit a property and the private stormwater management components being utilized to obtain the peak flow reduction. Audits will be as required, in response to a reported operational issue, or at least once within a 24 month period, as determined by Halifax Water.
Halifax Municipality is eligible for the credit program, provided they meet the established criteria:
- A stormwater management system(s), as noted above, has been installed on property owned by Halifax Municipality
- An engineered stamped stormwater management plan has been submitted, illustrating the area tributary to the stormwater management component, the amount of stormwater detained, annual application is required.
Credits will not be issued for private infrastructure installed to manage stormwater quality.
Over the years various design approaches have been used in meeting the detention requirements. The Halifax Water Design and Construction Specification current detention requirements. However, in order to recognize past and current methodologies and their associated benefits, Table 1 was developed.
Table 1 - Detention Credit
|Storms||Over Detain to Pre-Development||Match to Pre-Development||Credit Percent|
|1:5 Year||1:5 Year||1:5 Year||30%|
|1:10 Year||1:5 Year||1:10 Year||35%|
|1:25 Year||1:5 Year||1:25 Year||40%|
|1:50 Year||1:5 Year||1:50 Year||45%|
|1:100 Year||1:5 Year||1:100 Year||50%|
Standard detention design has two pathways:
- Discharging to the HRWC pipe system (Over Detention). In this approach higher level storms are detained on-site to meet the pre-development peak flow to the 1:5 YEAR STORM. That is, for example, the 1:100 year, 1:25 year, and 1:10 year post-development storms are detained such that the peak flow from the detention facility is no more than the pre-development 1:5 year storm.
- Discharging overland or to watercourses (Matching Detention). In this approach, all post development storms are detained such that the peak flow from the post-development site is MATCHING to the pre-development flows for each return period. That is, the 1:5 year post development flow matches the 1:5 year pre-development flow, and so on respectively for each of the higher level storms up to the 1:100 year storm.
Credit levels are determined based on a combination of volume retained and key return period storm reduction capabilities. No credit will be given for practices that do not reduce flows to either the 1:5 year level for the over-detention approach nor will credit be given for peak flow matching that does not include at least the 1:5 year storm. Table 1 provides credit amounts for over-detention designs or matching.
If an application is submitted for a storm not listed in Table 1, adjustments will be made to the credit to reflect the relative benefit to the system. The benefit to the system is not linear as reflected in the graph below:
Essentially, a 30% system benefit in detention relates to a 5% credit between the storms identified in the graph above. For the detention of storms not noted in Table 1, Halifax Water staff will prorate the credit utilizing data from the graph.
When a Customer applies and is approved for a credit, the Customer will receive the calculated amount of the credit in the form of a credit for each applicable billing period for the year.
For example if a Customer is billed on a monthly basis, and their stormwater Site Related Flow charge would normally be $5,000 a year, or $416.67 per month and they are eligible for a 30% credit, the $1,500 annual credit would be divided by 12 and a credit of $125 would appear on each monthly bill. For Customers billed on an annual or quarterly basis, the same credit will be applied in accordance with the frequency of billing. Halifax Water will coordinate the application of the credit to the bill or rebate as necessary with the Customer.
A reminder notice will be sent to the Customer two months prior to the annual expiry of the credit.
If a Customer fails to re-apply for the credit, they will be immediately removed from the credit program on the first day of the month following expiration of the first annual credit period. If as a result of Audit it is determined that a stormwater management system has not been properly maintained, the Customer will be given 30 days to provide a corrective action plan and 60 days to implement the plan. If the customer is still in a noncompliance situation, they will be removed from the credit program on the first day of the following month.