SW3190704_Add Info_20200429

Farkas, Jim J
From: Farkas, Jim J
Sent: Wednesday, April 29, 2020 8:04 AM
To: [e-mail]
Subject: SW3190704 - Skyland Drive Townhomes
Barry,
I took a look at what was submitted on March 161", 2020. Everything looks good except for the following:
- Original Comment 11— The provided SHWT report indicates that the SHWT is located somewhere below
elevation 669. The plans indicate that the excavated bottom of the sand filter will be at elevation 662.5 (the
boring is not deep enough to show the SHWT separation). In order to meet Sand Filter Minimum Design Criteria
1, a vertical separation of at least 2 feet between the lowest excavated point of the sand filter and the SHWT
must be shown (The boring must go at least as deep as elevation 660.5).
- The provided WQv calculations appears to be incorrect.
o Rv = 0.05 * 0.9 (60% Impervious) = 0.59
■ The equation is written incorrectly, it should be "Rv = 0.05 + 0.9 (% Impervious)"
■ The percent impervious area (60%) does not match the Supplement-EZ form (63%) or the post -
construction drainage area map (1.411 ac / 2.305 ac = 61%). Please revise all applicable
submittal items so all values coincide.
o WQv = 3630 * 1" * Rv * 4.335 ac = 4,819 cf
■ The drainage area to the sand filter (2.305 ac) should be used instead of 4.335 ac. Please
correct/recalculate this value as well as WQv adj and revise all applicable submittal items to
show the correct value.
Since these are really minor things, once I get the hard copies of anything that may have changed from addressing these
issues and the documents are uploaded to Laserfiche (Provided everything is still in order), we can issue the permit
without doing another formal 30-45 day review.
If you believe that it will take more than 30 days to get all of the resubmittal information to me (I understand that the
soil boring information may take some time to get), please reach out to me and ask for an extension, otherwise the
submission will be returned as incomplete if not resubmitted within 30 days.
Let me know if you have any questions.
Jim Farkas
Environmental Engineer
North Carolina Department of Environmental Quality
Division of Energy, Mineral, & Land Resources — Stormwater Program
512 N. Salisbury Street
1612 Mail Service Center
Raleigh, NC 27699-1612
[phone]
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