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Home My WebLink About20150615 Ver 1_Wet Pond Calcs_20151218 Strickland, Bev From:Devane, Boyd Sent:Friday, December 18, 2015 11:24 AM To:Strickland, Bev Subject:Please file this in 15-0615 Attachments:Rockingham Wet Pond Calcs 12152015.pdf From: Brian O'Kane \[mailto:bokane@bohlereng.com\] Sent: Friday, December 18, 2015 10:08 AM To: Devane, Boyd <boyd.devane@ncdenr.gov> Subject: RE: I did get the attachments. Boyd – I’ve attached the update wet pond spreadsheet. If you can take a quick look at this and the plans, I’d greatly appreciate it! I’m happy to discuss any concerns or big picture questions, and can get hard copies of the plans, full calculation booklet (with narrative, etc), and other updated paperwork to you asap. Thanks again for your help! Brian From: Devane, Boyd \[mailto:boyd.devane@ncdenr.gov\] Sent: Friday, December 18, 2015 9:51 AM To: Brian O'Kane <bokane@bohlereng.com> Subject: I did get the attachments. From: Brian O'Kane \[mailto:bokane@bohlereng.com\] Sent: Friday, December 18, 2015 9:46 AM To: Devane, Boyd <boyd.devane@ncdenr.gov> Subject: Rockingham Grocery Boyd – I’ve attached PDFs of the following plans: Cover Sheet Construction Details (2) – Shows cross section of the pond and Rip Rap Pad Existing Conditions Plan Site Plan Grading and Drainage Plan I’ll follow up with the calculations book in a separate email due to file size. These plans are the latest based on our iterations with NCDOT and keep all grading related to the pond out of the NCDOT Right-of-Way. Thanks, Brian 1 Brian O'Kane Bohler Engineering, NC, PLLC 4011 Westchase Boulevard, Suite 290 | Raleigh, NC 27607 P: 919-578-9000 l bokane@bohlereng.com Serving the East Coast Visit our new website! Confidentiality Note: This e-mail, and any attachment to it, contains confidential information intended only for the use of the designated recipients, which information may also be privileged. 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If you have received this e-mail in error, please notify the sender via reply e-mail and immediately delete this e-mail from your system. 2 BOHLER Project Information Wet Detention Basin Design Project: Rockingham Grocery Location: 705 U.S. 74 Business Project Number: NCR151000 Date: Dec -18-2015 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 = 1.00 in Driving Head (Hc) = 0.42 ft O orifice = 0.017 cfs Drawdown Time = 3.7 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