Approved LUMO Amendments: Stormwater Quality and Peak Flow Rate Requirements

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On May 1, 2024, Council adopted the amendments to LUMO Section 5.4.6 Stormwater Management that

address the peak flow rate requirements and
clarify the Total Suspended Solids (TSS) water quality requirements.

What are the adopted changes?

LUMO Section 5.4.6 includes the performance requirements for development and redevelopment.

The final adopted changes available online.

This performance objective...	... regulates this...	... using this Engineering Design Criteria.	The proposed amendments will make these changes.
Water Quality treatment	Total suspended solids (TSS) potentially caused by the development	85% pollutant removal from 1-inch rainfall	Clarify the TSS volume requirement
Peak Flow Control	How fast runoff flows off the site	1-year, 2-year, and 25-year, 24- hour rain event	Add the 100-year rain event
Peak Volume Control	How much runoff flows off the site	2-year, 24-hour rain event	No change

Developers meet these requirements by building Stormwater Control Measures (SCMs) to temporarily store and treat the excess stormwater runoff caused by adding hard (impervious) surfaces to the site. Ever noticed a pond near a new development? Then you've seen a stormwater control measure.

How many inches of rain counts as a 1-year storm?

To determine how much rainfall we can expect during a 1-year rain event (or any other duration), the Town uses data from the NOAA Atlas-14 Point Precipitation Frequency Estimates. These estimates are based on historical data and tell us how much rain is likely to occur within a specific time period.

For example, in Chapel Hill, if we receive approximately 2.96 inches of rain within a 24-hour period, we consider it a 1-year storm. This means that, based on past data, we can expect this amount of rainfall to happen at least once within a year.

How did the public share feedback prior to Council adopting the changes?

The public could

Email comments to Council at mayorandcouncil@townofchapelhill.org with "stormwater ordinance changes" in the subject line.
Share feedback during the Town Council's public hearing on March 20 and the regular meeting on April 24.

Staff held two hybrid public information meetings on February 13, 2024. Participants joined in person at the Library and online through Zoom.

What is the timeline?

June 2021

Several Council members presented a petition to the Town Council requesting a comprehensive review of the Town’s stormwater management regulations.

Fall 2022

The Town hired the firm SRF Consulting Group to complete a comprehensive review of the Town's stormwater regulations. They focused on the Town's post-construction stormwater management regulations as stated in the Land Use Management Ordinance 5.4 (LUMO 5.4).

SRF presented to several stakeholders to hear feedback on LUMO 5.4

November 14, 2022 – Town Council Work Session
November 14, 2022 and December 7, 2022 – Technical Advisory Committee Engagement Meetings
November 15, 2022 and December 7, 2022 – Community Open House
November 15, 2022 and December 1, 2022 – Professional Stakeholders Group Engagement

April 2023

SRF completed their report, which is available online. The recommendations include the proposed changes to LUMO 5.4.

May 2023

The Booker Creek Working Group finalized their report, including Recommendation 5: Modification to the Land Use Management Ordinance (LUMO) to Address the 100-Year Storm Event in Chapel Hill.

October 2023

Staff sent a summary of SRF’s report to Town Manager, Chris Blue.

November 2023

The Mayor and several Council members presented a petition to the Town Council requesting that the addition of the 100-year storm event be added to the regulations as soon as possible.

January 2024

Council called a Legislative Hearing on March 20 for consideration of the proposed changes to LUMO 5.4.

February 13, 2024

Staff held two hybrid public information meetings at the Chapel Hill Public Library and via Zoom. Drop-in hours were from 12:30-2:00 PM and 6:00-7:30 PM. Find more information on the Town Calendar.

Late February and Early March

Staff will present the proposed changes to the Stormwater Management Utility Advisory Board and the Planning Commission.

March 20, 2024

Council will hold the legislative hearing about the proposed text amendments to LUMO 5.4. Find more information on the Town Calendar.

May 1, 2024

Council adopted the proposed changes. The full text is available online.