SW5231001_Stormwater Report_20240404

MEETING MINUTES RS&I1
Subject: Park Economy 3 Post Construction Stormwater RDUAA No.: 080799
Permitting
Project: RDU Park Economy 3 Expansion RS&H No.: 1051-0068-002
Meeting Date: February 12, 2024 Prepared By: John Holmes
Location: RDUAA MOC Date: February 14, 2024
Comments
Incorporated:
Attendees
RDUAA: Ron Jewett, Bill Sandifer, France Campbell
RS&H: John Holmes, Tim Kennerly (Kennerly Engineering)
OTHERS: Jim Farkas (NCDEQ), Dr. Bill Hunt (NCSU), Caleb Mitchell (NCSU)
The purpose of this meeting was to discuss the comments received for the Park Economy 3 Expansion Post-
Construction Stormwater Permitting process from NCDEQ.
RS&H and NCDEQ discussed the comments received. NCDEQ pointed out the following two comments for
further discussion:
1. "5b. Specify a soil media mixture that meets the bioretention mixture requirements in lieu
of the provided wetland soils mixture."
• Mr. Farkas noted that the NCDEQ stormwater design manual contains an error and the specified
soil mixture for bioretention cells is incorrect. He stated that the statute is correct though and to
update the plans to that. He is going to send a link to the correct information. UPDATE: Link has
been received.
• Mr. Holmes stated that this will be updated in the plans.
• ACTION ITEM: RS&H to revise media mix.
2. "5d. Limit the ponding depth of the design volume to no more than 15" above the top of
the soil layer.
• Mr. Farkas stated his concerns about the temporary water depths exceeding 15-inches above the
soil level and the health of the wetland plants.
• Mr. Holmes cited the Mitchell et. al paper and that the plants selected were narrowed down from the
NCDEQ wetland plant list to plants that were better suited for temporary inundation. Mr. Holmes
also stated that the drawdown time is 24-72 hours but all SCMs would be under the 1-in event
depth within 24 hours as designed.
• Mr. Farkas asked why the weirs were being placed higher than the required treatment elevations.
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MEETING MINUTES RS&I1
• Mr. Holmes stated that RDU is seeking to exceed minimum treatment amounts based on their
Sustainability Management Plan (SMP) and is looking at fully treating 2-yr storm events and
attenuating 100-yr events, if possible.
• Dr. Hunt stated that 18 inches is typically acceptable without loss of plant life and greater depths
are allowable if more mature plants are planted and established. Dr. Hunt suggested allowing for an
adjustable weir to allow lower depths initially and then higher depths after establishment.
• Mr. Holmes stated that the adjustable weirs ultimately become a maintenance issue for the Airport
and are not desirable if possible.
• Dr. Hunt suggested potentially reducing some SCMs will maintaining the depths of others.
• Mr. Holmes suggested 1) lowering the weirs for 3 of the SCMs to reduce the ponding depth to 15-in,
2) keeping 2 SCMs at the current design, and 3) lowering the weirs of the remaining 2 SCMs to be
"somewhere in the middle" as a possible approach in order to study and evaluate the effects of
water depth on the plants. Weirs can ultimately be lowered in the future if problems persist.
• Mr. Farkas and Dr. Hunt both agreed that this would be a good approach.
• ACTION ITEM: RS&H to revise weir elevations accordingly.
Permitting Schedule: Mr. Campbell and Mr. Sandifer asked about the permitting schedule. Mr. Farkas stated
that a response has to be provided to the permit within 90 days. The response to comments was received by
NCDEQ on 1/24/2024. Mr. Farkas stated that RDU's place in the queue would remain the same but the revised
plan sheets could be submitted. Mr. Sandifer emphasized the importance of this project and this permit to the
success of the program.
These notes represent the items discussed and the conclusions reached during this meeting. Any request for
edits or modifications to the above notes shall be submitted in writing within five business days.
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