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10/07/2024 11:34 am

Sewer Capacity Studies

Downstream Sewer Capacity Analysis submittals and approval.

Updated: Oct 7, 2024

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Downstream Sewer Capacity Evaluation Downstream Sewer Capacity Study Data Request and Submittals Downstream Sewer Capacity Study Submittal Downstream Sewer Capacity Study Review and Approval Reimbursement Eligibility

Raleigh Water may determine during the rezoning, development plan, or building permit review process that the increase in sewer discharge associated with a project will exceed the available capacity of downstream sewer mains and that replacement of the existing downstream sewer mains may be required. Where adequate sewer capacity is a concern, a sewer study will be necessary. 

With projects that anticipate an increase in sewer discharge capacity, Raleigh Water may require a sewer main replacement be made. During the rezoning, development plan, or building permit review process, where adequate sewer capacity is a concern, Raleigh Water will require a sewer capacity study to make the replacement determination.

Downstream Sewer Capacity Evaluation

Developers must identify the proposed increase in sewer capacity.  The guidance below will help determine the necessity of a sewer capacity study:

  • The average daily sewer demand is 2,500 gallons per day or greater
  • A subdivision with 40 lots or more
  • Existing capacity is determined to be insufficient If a sewer capacity study is required, the reviewer will inform the applicant during the plan review process and revise the development plan to require a submittal for a study. The analysis should be made only from the project site to the nearest fifteen (15) inches or greater gravity main, and may include an analysis of pump stations, as well. The City may determine that the study extend further than the nearest fifteen (15) inch gravity main on a case-by-case basis.

An applicant must apply for data requests to begin a sewer study through the Permit and Development Portal. The Permit and Development Portal is a tool used to manage development review and permitting processes. Customers that apply for permits frequently are encouraged to set up a portal account. Please review the Permit and Development Portal Help Center page for information on accounts and payments.

Downstream Sewer Capacity Study Data Request and Submittals

To request a sewer capacity study, please follow these steps: 

1.  Apply for the Plan type under the Category Sewer Capacity Study Request (CAPS). 

2.  Provide the associated development plan, Property Identification Number (PIN) or address, and the estimated peak flow in gallons per day (GPD). 

3.  Submit the Utility Plan identifying the immediate downstream manhole and peak flow into the discharge manhole. If there are multiple points, each must be identified. 

4.  Once submitted, a review team member will provide the following information as an attachment in the portal: 

5.  Aggregated billing data to establish existing flow rates. 

6.  Pipe sizing and slope information, if available. 

7.  Where appropriate, developers may base the study on standard flow rates and minimum slopes to simplify calculations. 

8.  Developers may choose to install gravity sewer flow meters to obtain more accurate average daily and peak flow rates. These meters should capture sufficient wet weather events to determine peak flow. 

9.  If no existing data is available, developers may use their own survey data. 

Downstream Sewer Capacity Study Submittal

Please use this Standardized Template when submitting the Sewer Study together for review.  Once submitted, the applicant must:

  • Select their request case in the portal and choose the “Apply” option under Sub Records.
  • Ensure the design engineer is listed or submit the study as the design engineer.
  • Attach the Downstream Sewer Analysis Document, signed by the design engineer.
  • Pay the required submittal and review fee through the portal.

Downstream Sewer Capacity Study Review and Approval

After submission, City staff will review the Downstream Sewer Capacity Study and provide feedback through the Permit and Development Portal. Once the study is approved, any required updates or designs for sanitary sewer upgrades identified in the study must be incorporated into the Site Permit Review (SPR) or Construction Drawings for the Merger Community before final approval.

Reimbursement Eligibility

If sanitary sewer pipes need to be replaced because capacity exceeds 65% due to the proposed development, the developer may be eligible for reimbursement. The reimbursement amount is calculated using a spreadsheet provided by Raleigh Water, based on unit costs for upgrading the sewer main, which are updated annually. 

Raleigh aims to reimburse upgrades based on the remaining capacity in each pipe before the development and the additional capacity provided to the City for future development flow.

Developers can apply for reimbursement through the Permit and Development Portal once the upgraded pipes have been installed, inspected, and conditionally accepted by Raleigh.
 

Visit the Steps for Raleigh Water Reimbursement Requests to begin the process. 

Contact

 

For further questions about the sewer capacity studies process related to land development:
Raleigh Water Development Review Team

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