20150615 Ver 1_Wet Pond Calcs_20160427

Strickland, Bev
From:Devane, Boyd
Sent:Wednesday, April 27, 2016 10:57 AM
To:Strickland, Bev
Subject:FW: Rockingham Grocery stormwater plans #15-0615
Attachments:Rockingham Wet Pond Calcs 160426.pdf
Please file this in #15-0615 thanks.

NC Division of Water Resources
919-807-6420

From: Andrew Allison \[mailto:[e-mail]\]
Sent: Wednesday, April 27, 2016 9:56 AM
To: Devane, Boyd <[e-mail]>
Cc: Turlington, Chad <[e-mail]>; Andrew Moriarty <[e-mail]>; Wyatt Bone
<[e-mail]>; [e-mail]
Subject: RE: Rockingham Grocery stormwater plans #15-0615

Boyd,

I have attached the updated calculations that now include all three pages. We have changed the orifice diameter to
1.25”. Our calculations show that with a 1.5” orifice the drawdown time would become 1.6 days. We have opted to
reduce the orifice to 1.25” in order to stay within the 2 to 5 day drawdown time period. Our detail was modified
accordingly.

You should receive a link to our full set of plans. We will mail hard copies that are signed and sealed. How many copies
will you require?

Chad,

Three (3) original copies of the O&M agreement will be mailed directly to you if that is okay.

Thanks!

Andrew Allison, E.I.
Bohler Engineering NC, PLLC
4011 Westchase Boulevard, Suite 290, Raleigh, NC 27607
[phone]

From: Devane, Boyd \[mailto:[e-mail]\]
Sent: Monday, April 25, 2016 4:34 PM
To: Andrew Allison <[e-mail]>
Cc: Turlington, Chad <[e-mail]>
Subject: FW: Rockingham Grocery stormwater plans #15-0615

Thanks for your call offering help. This has been a confusing situation.

1

th
Brian sent me a wet pond spread sheet on December 18 that had three pages. Because of a discrepancy in the orifice
size with the plan sheets, I asked him to check into it and resubmit the information with corrections. I also included a
stth
copy of the updated calculations on April 1 so he could see what I received. (See attached) I wrote him back on the 4
th
of April and said: “The Wet Pond calculations page in the March 24 Letter of Transmittal had two pages entitled “Wet
Detention Basin Design”. Did you omit the second page in your submittal on Friday?”

He wrote back on 4/19 and said that “The second page included the stage-storage volume of the pond and is attached to
the email that you sent me.”

As I tried to explain, the earlier submittal contained 3 pages and the later (attached above) had two. After some study, I
realized that the updated page that he failed to resubmit had the project area and runoff volume calculations. Maybe
that page was correct but I wanted him to send me all three pages (preferably with page numbers and dates) so I would
know what the official submittal was.

st
He also said in his April 1 email that “We will update the plan sheet accordingly and get you updated copies.” I have
never received the updated page(s) that had the correction of 1.5” orifice.

st
Also, as Chad’s March 1 email (below) indicated, we need three copies of the signed and notarized O&M agreement. I
have not seen that.

Perhaps I’m missing something and the proper information was sent. Please have Brian call and explain if I have missed
something. If not, send the final wet pond calculations and corrections to any of the plan sheets that are needed
because of the orifice discrepancy. Thanks.

From: Turlington, Chad \[mailto:[e-mail]\]
Sent: Tuesday, March 01, 2016 2:44 PM
To: Brian O'Kane <[e-mail]>
Subject: MGP Rockingham Retail

Brian,
The following items are what Boyd said that were needed to process the stormwater component of the 401 Application
for the MGP Rockingham Retail 401 application.

1.Four paper copies of the plans and specs (on 24” x 36” sheets).

2.One disc containing copies of the plans and specs.

3.The original and 3 copies of a signed (and notarized) O&M agreement.

4.Four copies of all stormwater calculations for the sizing of the stormwater treatment device.

NC Division of Water Resources
919-807-6420

From: Brian O'Kane \[mailto:[e-mail]\]
Sent: Friday, April 01, 2016 7:36 AM
To: Devane, Boyd <[e-mail]>
Cc: Turlington, Chad <[e-mail]>
Subject: RE: Rockingham Grocery stormwater plans #15-0615

Boyd – Here’s a copy of the latest spreadsheet in PDF version. We had to reduce the size of the draw-down orifice to 1”
to meet the requirements for draw-down time. We will update the plan sheet accordingly and get you updated
2

copies. Let me know if you see anything else that you need changed or if you want us to make this change and resend
the sheets.

Thanks!
Brian

From: Devane, Boyd \[mailto:[e-mail]\]
Sent: Thursday, March 31, 2016 2:30 PM
To: Brian O'Kane <[e-mail]>
Cc: Turlington, Chad <[e-mail]>
Subject: RE: Rockingham Grocery stormwater plans #15-0615

Just wanted to let you know that I never received anything you were going to send last Thursday. Did you send it?

NC Division of Water Resources
919-807-6420

From: Brian O'Kane \[mailto:[e-mail]\]
Sent: Monday, March 28, 2016 7:49 AM
To: Devane, Boyd <[e-mail]>
Cc: Turlington, Chad <[e-mail]>
Subject: RE: Rockingham Grocery stormwater plans #15-0615

Thanks Boyd. I will send them over to you today.

From: Devane, Boyd \[mailto:[e-mail]\]
Sent: Thursday, March 24, 2016 5:18 PM
To: Brian O'Kane <[e-mail]>
Cc: Turlington, Chad <[e-mail]>
Subject: Rockingham Grocery stormwater plans #15-0615

Today, I received four copies of the drawings for the stormwater plan for the Rockingham Grocery project. The plans did
not include an updated “Wet Detention Basin Design” calculations sheet. We received a copy of the calculations that
was dated Dec 18, 2015 but it does not seem to have been updated to reflect the drawings. In just a quick look, I did
th
notice the orifice drawings showed a 1.5” draw-down orifice and the December 18 Wet Detention Basin Design sheets
showed a 1.0” draw-down orifice. Please send me copy of the engineering calculations for the wet detention basin that
you intend to apply to the drawings that I received today. You can email them to me at [e-mail].
Thanks

NC Division of Water Resources

NC Division of Water Resources
919-807-6420

From: Brian O'Kane \[mailto:[e-mail]\]
Sent: Friday, April 01, 2016 7:36 AM
To: Devane, Boyd <[e-mail]>
Cc: Turlington, Chad <[e-mail]>
Subject: RE: Rockingham Grocery stormwater plans #15-0615

3

Boyd – Here’s a copy of the latest spreadsheet in PDF version. We had to reduce the size of the draw-down orifice to 1”
to meet the requirements for draw-down time. We will update the plan sheet accordingly and get you updated
copies. Let me know if you see anything else that you need changed or if you want us to make this change and resend
the sheets.

Thanks!
Brian

From: Devane, Boyd \[mailto:[e-mail]\]
Sent: Thursday, March 31, 2016 2:30 PM
To: Brian O'Kane <[e-mail]>
Cc: Turlington, Chad <[e-mail]>
Subject: RE: Rockingham Grocery stormwater plans #15-0615

Just wanted to let you know that I never received anything you were going to send last Thursday. Did you send it?

NC Division of Water Resources
919-807-6420

From: Brian O'Kane \[mailto:[e-mail]\]
Sent: Monday, March 28, 2016 7:49 AM
To: Devane, Boyd <[e-mail]>
Cc: Turlington, Chad <[e-mail]>
Subject: RE: Rockingham Grocery stormwater plans #15-0615

Thanks Boyd. I will send them over to you today.

From: Devane, Boyd \[mailto:[e-mail]\]
Sent: Thursday, March 24, 2016 5:18 PM
To: Brian O'Kane <[e-mail]>
Cc: Turlington, Chad <[e-mail]>
Subject: Rockingham Grocery stormwater plans #15-0615

Today, I received four copies of the drawings for the stormwater plan for the Rockingham Grocery project. The plans did
not include an updated “Wet Detention Basin Design” calculations sheet. We received a copy of the calculations that
was dated Dec 18, 2015 but it does not seem to have been updated to reflect the drawings. In just a quick look, I did
th
notice the orifice drawings showed a 1.5” draw-down orifice and the December 18 Wet Detention Basin Design sheets
showed a 1.0” draw-down orifice. Please send me copy of the engineering calculations for the wet detention basin that
you intend to apply to the drawings that I received today. You can email them to me at [e-mail].
Thanks

NC Division of Water Resources
919-807-6420

4

BOHLER
Project Information
Wet Detention Basin Design
Project: Rockingham Grocery
Location: 705 U.S. 74 Business
Project Number: NCR151000
Date: Apr -26-2016
Designed: KW
Checked: WLB
Site Information
Sub Area Location: Wet Detention Basin 1
Drainage Area (DA) = 109,791 Sf
Impervious Area (IA) = 89,308 Sf
Percent Impervious (1) = 81.3 %
Elevations
Top of Bank Elevation =
264.00 ft
Emergency Elevation =
263.00 ft
Temporary Pool Elevation =
260.29
Permanent Pool Elevation =
259.00 ft
Bottom of Pond Elevation =
253.00 ft
Sediment Cleanout, Bottom Elevation =
253.00 ft
Basin Areas/Volumes
Area of Permanent Pool =
4,297 sf
Area of Bottom of Shelf =
3,156 sf
Area of Bottom of Pond =
106 sf
Area of Temporary Pool =
6,336 sf
Volume, main pool =
7,257 cf
Volume, forebay (sum of forebays) =
1,614 cf
Volume, permanent pool =
8,871 cf
Forebay % of permanent pool volume =
18.2 %
Average Depth
Depth of Pond =
5.5 ft
Average Depth =
3.28 ft
Use Average Depth of =
3.00 ft
Aperm pooh (includes main pond & forebays) (Elev = 259.00 )
A bot shelf (includes main pond & forebays) (Elev = 258.50 )
Abot_pond (excluding sediment storage & forebays)
A temp_p-d (includes main pond and forebays) (Elev = 260.29 )
V malnl,00l (from Hydraflow)
V forebay (from Hydraflow)
V penn_,00l (Vforebay+Vmainyool)
OK
Depth (dist. btwn. bot. of shelf & btm. of pond, excludes sediment)
Round down to nearest 0.5
Required Surface Area - Wetland
SA/DA = 3.36 (85% TSS Removal via Pond)
Min Req'd Surface Area = 3,689 sf (at Permanent Pool)
Required Storage Volume - Using Simple Method
Design Storm = 1.0 inch (Project Does Not Drain to SA Waters)
Determine Rv Value = 0.05 + 0.009 (1) = 0.78 in/in
Storage Volume Required = 7,156 cf (above Permanent Pool)
Side Slopes of Pond = 3 :1
Is Permenant Pool Surface Area Sufficient (yes/no)? Yes ( 4297 > 3689 ) sf

BCH LER
V N C I N E I'. R f N C
Wet Detention Basin Design
1.0 inch Volume Elevation
Required Temporary Pool Volume = 7,156 cu ft
Temporary Pool Lower Elevation Bound =
260.00
Temporary Pool Upper Elevation Bound =
261.00
Temporary Pool Lower Volume Bound =
5,186 cu ft
Temporary Pool Upper Volume Bound =
12,052 cu ft
Temporary Pool Elevation = 260.29
Orifice Sizing - Wet Detention
02 Days = 0.0415 cfs
05 Days = 0.0124 cfs
Orifice Size = 1.25 in
Driving Head (Hc) =
0.41
ft
O orifice =
0.026
cfs
Drawdown Time =
2.4
days
less than 5 days (yes/no) ?
Yes
0
greater than 2 days (yes/no) ?
Yes
259.50
Anti -Flotation Device
2,470
2,470
Outside Length =
4.00
ft
Outside Width =
4.00
ft
Inside Length =
3.00
ft
Inside Width =
3.00
ft
6745
Bottom Thickness =
0.50
ft
Top of Riser =
261.00
ft
Invert of Riser =
257.97
ft
Area =
16.0
sf
Volume =
56
cf
Weight =
3,524
lbs
Factor of Safety =
1.10
WT Req'd of Anti -Flotation Device =
3,877
lbs
Volume of Concrete Req'd =
44.3
cf
Depth Provided =
1.00
ft
Volume Provided =
45.2
cf
WT of Anti -Flotation Device Provided =
3,960
lbs
Contour
Contour
Area
Incremental Accumulated
Volume Volume, S
Stage, Z
sq ft
cu ft
cu ft
ft
259.00
4302
0
0
0.0
259.50
5577
2,470
2,470
0.5
260.00
6045
2,906
5,375
1.0
260.29
6335
1,795
7,170
1.3
261.00
6745
4,643
11,814
2.0
262.00
7565
7,155
18,969
3.0
263.00
8425
7,995
26,964
4.0
264.00
9325
8,875
35,839
5.0
(Flowrate required for a 2 day drawdown)
(Flowrate required for a 5 day drawdown)
(Diameter)
0
(Outside Dim. = 4 -ft x 4 -ft, Inside Dim. = 3 -ft x 3 -ft)
(Water Displaced - Top of Riser to Bottom of Riser)
(Weight Water Displaced)
(Unit WT of Concrete = 150 pcf) Submerged Concrete Unit Weight 87.6 pcf
(4 -ft x 4 -ft Box filled 1.00 -ft deep with concrete)
OK

)rebav volume
Contour
Contour
Area
Accumulat
Increment ed
al Volume Volume, S
Stage, Z
sq ft
cu ft
cu ft
ft
255.00
99
0
0
0.0
256.00
222
161
161
1.0
257.00
379
301
461
2.0
258.00
569
474
935
3.0
259.00
789
679
1,614
4.0
Contour
Contour
Area
Accumulat
Increment ed
al Volume Volume, S
Stage, Z
sq ft
cu ft
cu ft
ft
253.00
106
0
0
0.0
254.00
301
204
204
1.0
255.00
590
446
649
2.0
256.00
962
776
1,425
3.0
257.00
1,600
1,281
2,706
4.0
258.00
2,176
1,888
4,594
5.0
258.50
2,481
1,164
5,758
5.5
259.00
3,513
1,499
7,257
6.0