Smoke Bomb Hill AAFES Mini-Mall Express

From: Branch Smith
To: Randall, Mike; Ward. Lee P CIV USARMY IMCOM ATLANTIC (US); David Heins (david.a.heins.civCd)mail.mil)
Subject: RE: Smoke Bomb Hill AAFES Mini -Mall Express
Date: Monday, March 30, 2015 3:10:12 PM
Attachments: 2222 001.odf
Mike:
I see there were a few numbers reported incorrectly. Sorry about that. Also, the intent of this
SW design needs clarification. As you'll see from the revised pages and DA Map, the drainage
area AAFES wants to treat within the BMP (Infiltration Basin) is only what they are
redeveloping. Out of the total project area of 6.65 acres, 6.20 acres is going to the Infiltration
Basin. Out of the 6.20 acres, about 54% is impervious, which results in the revised treatment
storage of about 21,752 cf. The provided storage is above this at 22,484 cf, so we should be
ok. There is approx. 22 acres (based on a rough GIS storm drainage area) that supposedly
comes through this infiltration basin. So that is offsite, but I didn't include any offsite in these
numbers. Not sure how you report this?
Take a look at these revised numbers and let us know.
Thanks
Branch
From: Randall, Mike [mai Ito: mike. [e-mail]]
Sent: Friday, March 27, 2015 10:20 AM
To: Ward, Lee P CIV USARMY IMCOM ATLANTIC (US); David Heins ([e-mail]); Branch
Smith
Subject: Smoke Bomb Hill AAFES Mini -Mall Express
I have some questions regarding the Smoke Bomb Hill AAFES Mini -Mall Express Application form and
Supplement Form.
Page 3 of 6 of the application form.
1. The total Drainage area is identified as 431,375 ft2 (or 9.9 acres) the Total property is 6.65
acres. I take that to mean that the additional drainage area is outside the "Property Area"
2. The onsite drainage area is 289,888 and the offsite drainage area is 746,122 (1,036,010).
The Onsite Drainage area and Offsite Drainage Area (1,036,010) should equal the Total
Drainage Area (431,375)?
3. The Proposed Impervious Area (275,402) should equal the Total Impervious Surface Area
(222,156)?
The supplement form indicates that the both the Drainage Area and the Impervious Area is 222,156?
It appears that the Water Quality Treatment Volume Provided (22,484 ft 3) is not adequate based on
the P95 Storm, BUA and DA?

Volume = 3630 * Rd * Rv * Ac
Where Ac=(Drainage Area in sf)/43,560 sf/ac = 431,375 ft2 /43,560 ft2/ac = 9.9 acres
Rd = Design Storm = 1.8 in (Fort Bragg)
I = Impervious Portion / Drainage Area = 222,156/431,375 = 51.5 %
Rv=0.05+(0.9 * 1)=0.05+(0.9 *0.515)=51.34
Fort Bragg requirement to meet the Energy Independence and Security Act, Section 438
95th % rainfall event (1.8 inches)
Volume Fort Bragg 95%storm= 3630 * 1.8 * 0.51 * 9.9 Acres= 33,000 W
Estimate volume provided 180 ft * 40 ft * 3.0 feet deep = 21,600 ft3
Mike Randall
Stormwater Permitting Program
INC Division of Energy, Mineral and Land Resources (DEMLR)
1617 Mail Service Center
Raleigh, INC 27699-1617
Office: 919-807-6374
Cell: 919-389-7801
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