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CC - Storm Drainage Calcs Storm rN: . lm '9 t fO . LAVENDER HEIGHTS SUBDIVISION NO. 3 Meridian, ID AL � ..� T 042 f0 . 7/07/2021 Civil Innovations® PLLC 1043 E. Park Blvd.Ste. 101 Boise, ID 83712 Phone: (208) 884-8181 www.civil-innovations.com Introduction The Lavender Heights Subdivision is located on approximately 55 acres on the North Side of Lake Hazel Road approximately%mile east of Locust Grove Road. Lavender Heights Subdivision No. 3 is third of four expected phases. Existing Storm Drain Conditions The area that makes of Lavender Heights No.3 was farmed previously. Irrigation has been accomplished with sprinklers and so there are no existing drainage systems in place. Proposed Storm Drain Design Storm water runoff from Lavender Heights will flow overland into seepage beds located under the sidewalk and planter strips between the curb and sidewalk and in common lots where possible. The calculations that follow show that the proposed seepage beds are of adequate size to handle runoff from this development as required by the 2017 drainage policy. Weighted runoff coefficients, or"C" values, are determined by calculating by applying a value of 0.24 for pervious areas and 0.95 for impervious areas over each drainage basin where no home lots are included. A"C"value of 0.4 was used where homes are located. A design infiltration rate of 8" per hour was utilized for the seepage bed calculations. The soil profiles done on the site show pit run gravel starting at depths between 47 and 64 inches below existing ground level. The pit run soils should produce infiltration rates well in excess of 8 inches per hour. No groundwater has been encountered on this site to data. 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No. 3 Seepage Bed Calculations SG # Basins High Flow Bypass Design Storm Design Flow SG Size C.F.S. 10 10A+ 10B No 100 3.87 1500 11 11A+ 11B No 100 3.13 1000 12 12A+ 12B No 100 2.29 1000 13 13A+ 136 No 100 4.04 1500 1000 Gallon = 3.33 CFS 1500 Gallon =4.15 CFS Lavender Heights Subd. No. 3 Pipe Sizing Calculations DI#10A to DI#1013 Q(25)= 1.66 CFS Slope= 0.0085 Diameter= 12 inch Mannings "n" = 0.012 A= 0.79 sgft P= 3.14 ft R= 0.25 Full Flow Capacity= 3.57 CFS OK DI#1013 to SG#10 Q(25)= 2.76 CFS Slope= 0.0067 Diameter= 12 inch Mannings"n" = 0.012 A= 0.79 sgft P= 3.14 ft R= 0.25 Full Flow Capacity= 3.17 CFS OK Lavender Heights Subd. No. 3 Pipe Sizing Calculations DI #11A to DI#1113 Q(25) = 0.96 CFS Slope= 0.0085 Diameter= 12 inch Mannings "n" = 0.012 A= 0.79 sqft P= 3.14 ft R= 0.25 Full Flow Capacity= 3.57 CFS OK DI #11B to SG#11 Q(25) = 2.24 CFS Slope= 0.0072 Diameter= 12 inch Mannings "n" = 0.012 A= 0.79 sqft P= 3.14 ft R= 0.25 Full Flow Capacity= 3.28 CFS OK Lavender Heights Subd. No. 3 Pipe Sizing Calculations DI#12A to DI#1213 Q(25) = 1.02 CFS Slope = 0.0085 Diameter= 12 inch Mannings "n" = 0.012 A= 0.79 sqft P = 3.14 ft R= 0.25 Full Flow Capacity= 3.57 CFS OK DI#12Bto SG#12 Q(25) = 1.64 CFS Slope = 0.0072 Diameter= 12 inch Mannings"n" = 0.012 A= 0.79 sqft P= 3.14 ft R= 0.25 Full Flow Capacity= 3.28 CFS OK Lavender Heights Subd. No. 3 Pipe Sizing Calculations DI#13A to DI#13B Q(25) = 1.43 CFS Slope = 0.0085 Diameter= 12 inch Mannings "n" = 0.012 A= 0.79 sqft P= 3.14 ft R = US Full Flow Capacity= 3.57 CFS OK DI#13B to SG#13 Q(25) = 2.91 CFS Slope= 0.0085 Diameter= 12 inch Mannings"n" = 0.012 A= 0.79 sqft P= 3.14 ft R= 0.25 Full Flow Capacity= 3.57 CFS OK Lavender Heights Subd. No. 3 Seepage Bed Calculations Seepage Bed#10 (in common lot) V(100) DI#10A= 4230.0 CF V(100) DI#1013= 2751.0 CF V(100) = 6981.0 CF V(100) - Infiltration Volume 5711.0 Storage Required 5711.0 CF Bed Width 15.0 FT Bed Length 127.0 FT Bed Depth 7.50 FT Total Drainrock Footprint 14288 CF 18" Pipe Volume 224.3 CF Pipe Storage Volume 112.2 CF Drain Rock Volume 14063.2 CF Void Ratio 0.40 Drain Rock Storage 5625.3 CF Storage in Pipe 112.2 CF Storage in Drainrock 5625.3 CF Total Storage 5737.4 Time to Drain Infiltration Rate= 8.0 In/Hr Infiltration Area = 1905.0 SF Infiltration Volume= 1270.0 CF/Hr V(100) = 6981.0 CF V(100) - Infiltration Volume 5711.0 Time To Drain = 5.50 Hr Lavender Heights Subd. No. 3 Seepage Bed Calculations Seepage Bed#11 (in right-of-way) V(100) DI#11A= 2433.0 CF V(100) DI#11B= 2931.0 CF V(100) = 5364.0 CF V(100)- Infiltration Volume 3914.0 25%Sediment 978.5 CF Storage Required 4892.5 CF Bed Width 15.0 FT Bed Length 145.0 FT Bed Depth 5.60 FT Total Drainrock Footprint 12180 CF 18" Pipe Volume 256.1 CF Pipe Storage Volume 128.1 CF Drain Rock Volume 11923.9 CF Void Ratio 0.40 Drain Rock Storage 4769.6 CF Storage in Pipe 128.1 CF Storage in Drainrock 4769.6 CF Total Storage 4897.6 Time to Drain Infiltration Rate= 8.0 In/Hr Infiltration Area = 2175.0 SF Infiltration Volume= 1450.0 CF/Hr V(100) = 5364.0 CF V(100) - Infiltration Volume 3914.0 Time To Drain = 3.70 Hr Lavender Heights Subd. No. 3 Seepage Bed Calculations Seepage Bed#12 (in right-of-way) V(100) DI#12A= 2474.0 CF V(100) DI#1213= 1161.0 CF V(100)= 3635.0 CF V(100)- Infiltration Volume 2695.0 25%Sediment 673.8 CF Storage Required 3368.8 CF Bed Width 15.0 FT Bed Length 94.0 FT Bed Depth 6.00 FT Total Drainrock Footprint 8460 CF 18" Pipe Volume 166.0 CF Pipe Storage Volume 83.0 CF Drain Rock Volume 8294.0 CF Void Ratio 0.40 Drain Rock Storage 3317.6 CF Storage in Pipe 83.0 CF Storage in Drainrock 3317.6 CF Total Storage 3400.6 Time to Drain Infiltration Rate = 8.0 In/Hr Infiltration Area = 1410.0 SF Infiltration Volume= 940.0 CF/Hr V(100) = 3635.0 CF V(100)- Infiltration Volume 2695.0 Time To Drain = 3.87 Hr Lavender Heights Subd. No. 3 Seepage Bed Calculations Seepage Bed#13 (in right-of-way) V(100) DI#13A= 3332.0 CF V(100) DI#13B= 3497.0 CF V(100) = 6829.0 CF V(100) - Infiltration Volume 5069.0 25%Sediment 1267.3 CF Storage Required 6336.3 CF Bed Width 15.0 FT Bed Length 176.0 FT Bed Depth 6.00 FT Total Drainrock Footprint 15840 CF 18" Pipe Volume 310.9 CF Pipe Storage Volume 155.4 CF Drain Rock Volume 15529.1 CF Void Ratio 0.40 Drain Rock Storage 6211.7 CF Storage in Pipe 155.4 CF Storage in Drainrock 6211.7 CF Total Storage 6367.1 Time to Drain Infiltration Rate= 8.0 In/Hr Infiltration Area = 2640.0 SF Infiltration Volume= 1760.0 CF/Hr V(100) = 6829.0 CF V(100) - Infiltration Volume 5069.0 Time To Drain = 3.88 Hr I UNPLATTED BLACKROCK DRAINAGE AREA SW1 BLACKROCK Q SUBDIVISION NO.1 (TO"PRIVATE SEEPAGE BEDS" SUBDIVISION NO.1 mmil PSB1 THRU PSB13) mmil 38,362 S.F./0.88 ACRE EP do � ------ _- EP EP -_BLOFL ___��- -�� EP / EP 23 40 do 10 to LU 00 i ♦� � � � � � � � � � � � 1 m m m � � � � � � � � � �i � � � � � � � � � � � � � � � � ■i=�`" � � � � � � � � -- �� � � � � �mv-im °� �=ice 1 O N N i/ ♦ 15 16 to liz- 17 18 1 21 1 o I 1 1 ti C ' ,to 1 19 Y0 1 24 BLOCK 2 1 1 1 1 1 J amo °00 m° 1 DRAINAGE AREA 13A 1 LAVENDER HEIGHTS 1 I DRAINAGE AREA 5A 1 1 1 1 Q Y ,BLOCK 2 DRAINAGE AREA 12A 1 1 O SUBDIVISION NO.3 I DRAINAGE AREA 6A DRAINAGE AREA 7A L 14 105,008 S.F./2.41 ACRE °� 1 I 117,814 S.F./2.70 ACRE 1 1 1 1 IMPRESSIVE EAST RIDGE ' a �„ _> W 78,177 S.F. / 1.79 ACRE 1 1 49,004 S.F. / 1.12 ACRE 49,749 S.F./ 1.14 ACRE SUBDIVISION NO.1 o LIJ W LAVENDER HEIGHTS LAVENDER HEIGHTS 1 I EXISTING LAVENDER 1 I1 I O m z 3 1 1 SUBDIVISION HEIGHTS 1 SUBDIVISION N0.3 1 ° EXISTING LAVENDER EXISTING LAVENDER Ld o 3 0 1 HEIGHTS SUBD.NO.1 1 HEIGHTS SUBD. NO. 1 1 HEIGHTS SUBD.N0.1 1 1 M = ► I - ► DI 12A i - E.BRACE ST. - DI 13A DI 5A EXISTING E.BRACE DR. DI 6A f DI 7A f 1 ► - - - - - - - - - s - - 1 DI 126 i DI, \ - - -----------DI 5B -------------- -DI 6B f DI 7B--f-- 1 J ' w ► - - - - LAVENDER HEIGHTS EXISTING LAVENDER - - - ' 1 ► SB 12 - -SB 13 SUBDIVISION NO.3 HEIGHTS SUBD.NO.1 EXIST.SB 5 EXIST.SB 6 ` -EXIST.SB 7- 1 ► 13 -- -- o 0 1 DRAINAGE AREA 12B DRAINAGE AREA 13B } } Cj 36,631 S.F. / 0.84 ACRE 110,411 S.F. / 2.53 ACRE j } w ► BLOCK 10 BLOCK 10 28 } DRAINAGE AREA "OFFSITE" 2 3 4 5 6 1 7 8 9 10 11 12 13 14 - - - - °O 1 ► Uj LAVENDER HEIGHTS W DRAINAGE AREA 5B D A NAG A EA 6B Ln 1-: T - 4,173 S.F. / 0.10 ACRE a SUBDIVISION NO.3 W ww ► 12 W a 1 56,675 S.F./ 1.30 ACRE 133,932 S.F./3.07 ACRE }I } 1 1� ► v = 29 EXISTING LAVENDER EXISTING LAVENDERco min 1 1 ► LU 1 a i HEIGHTS SUBD.NO.1 HEIGHTS SUBD.NO.1 �- 1 ' ► 1 26 BLOCK 25 10 24 23 22 21 20 19 18 17 1 BL016 10 15 vs DRAINAGE AREA 7B 1 1 w a 52,634 S.F. / 1.21 ACRE 1 Iw " ► y }DRAINAGE AREA 11A 1 30 1 a Z} 1 EXISTING LAVENDER 1 IMPRESSIVE EAST RIDGE I ► 11 76,725 S.F. / 1.76 ACRE 1 m Q DRAINAGE AREA 8A HEIGHTS SUBD.N0.1 1 ; SUBDIVISION NO. ��oNAL �� 1 ► w DRAINAGE AREA 8B 82,842 S.F. / 1.90 ACRE 1 �� CXSTE �f 1 ► \ : . ... ... .. a 64,683 S.F./ 1.48 ACRE c EXISTING LAVENDER 1 ; 4� d p HEIGHTS SUBD.NO. �� UW DI 11A1 f f E. MAINACHT ST. f i 31 EXISTING LAVENDER N 1 �I f f yiou HEIGHTS SUBD.NO.2 X 1 1 ► \ -- = o W 1 1 1 ���071071.2 1 ► SB 11 LAVENDER HEIGHTS EXISTING LAVENDER CDw 1 1 � OF 'W W ► BLOCK 2 LAVENDER HEIGHTS _I_ SUBDIVISION N0.3 HEIGHTS SUBD �.N0.1 x 1- 1 1 1 ► 10 + + DRAINAGE AREA 10A SUBDIVISION N0.3 W �����-�-�� MIN P• 1 ► I W 133,493 S.F. / 3.06 ACRE BLOCK 3me WOUIN"I in m ► DRAINAGE AREA 11B a 7 8 9 10 11 12 13 4- -, + + 33 1 __ 1 1 w ♦ 92,432 S.F. / 2.12 ACRE - � __ -- 1 1 1 o J LAVENDER HEIGHTS I11 C013 f 6 LAVENDER HEIGHTS __ 1 DRAINAGE AREA SW2 1 W w m= oz SUBDIVISION NO.3 SUBDIVISION N0.3 BLOCK 2 1 f 1 1 z a o } Fq cc 34 j� DRAINAGE AREA 4A 35,435 S.F. / 0.81 ACRE o >- Q m Fq - c -- / _ �, 9 8 7 y BLOCK 3 j II II b a i \ ti , 6,526 S.F. / 0.15 ACRE, EXISTING LAVENDER 1 W z z �` �, 1 5 4 3 2 EXISTING LAVENDER FUTURE _ _ i HEIGHTS SUBD. N0.2 1 o z I ocw � HEIGHTS SUBD.N0.1 POOL SITE N I 11 1 z " cn Fp I cri 1 1 0/4q ♦ o 0 0 o z `F`\ LAVENDER HEIGHTS I --- EXIST � 1 L w CD FFp SUBDIVISION N0.3 - W 1 z o °C C) _ EXISTIN \` o 0 LU 0 `\ DI 10A t E.PHENOMENAL ST. I f EXISTING E.PHENOMENAL ST. i DRAINA E AREA 4B TIN Hl��o� 1 C Cn W w Fa UNPLATTED `F D. DI 10B ��f - - - -� i 14,880 S.F. /0.34 ACRE a EXISTING LAVENDER Ep TSB y0 .,• I ` L \� HEIGHTS SUBD.N0.1 ti \ 1 0 1 w Q o / -- - DRAINAGE AREA 10B W Ep\ V I EXISTING LAVENDER y� / DRAINAGE AREA 3 \ ~ z Ep 86,545 S.F. / 1.99 ACRE 1 \ 72 844 S.F. / 1.67 ACRE BLOCK 2 HEIGHTS SUBD.N0.1 ti 5 I EXISTING LAVENDER 1 1 `�\Ep ♦ - 4� I HEIGHTS SUBD. NO. 1 1 DRAINAGE AREA 2A Dl3 �EXI HEIGHTS SUB EXISTING VDENDER.NO 2 �� UNPLATTED • 1 1 76,902 S.F./ 1.77 ACRE STINGA�cEv_ Fp \ * 1 \ EXISTING LAVENDER \ j EP O HEIGHTS SUBD.N0.1 EXIST.TEMPORARY Fp \\ DRAINAGE POND Ep TO BE REMOVED p / � > _ \ DRAINAGE AREA 9A � Z \ \ \ 58,373 S.F./ 1.34 ACRE EXISTING LAVENDER \ \\EXIST SS 2 ti �126 i EXISTIN HEIGHTS SUBD.N0.2 1 CA DRAINAGE AREA LEGEND ` \ \ \E�A�ENSO i DRAINAGE AREA 2B \ ti I \(EST. Ir2A DRAINAGE AREA IDENTIFICATION NO. 133,977 S.F. / 3.08 ACRE y a /9q 0 EXISTING LAVENDER 4 , z 0.00 AC DRAINAGE AREA (ACRES) + + �/ HEIGHTS SUBD.NO. EXjS D196 \ / O= cm-ATIONs DRAINAGE AREA BOUNDARY ����_ /I T SB9 NORTH - �' o w y z a low / DRAINAGE AREA 913 y QLU o - - CD �' ♦ 147,330 S.F./3.38 ACRE \ w 1 DRAINAGE AREA PLAN I EXISTING LAVENDER 1 = UNPLATTED m HEIGHTS SUBD N0 2 o SCALE: 1" = 80'-0"HORIZONTAL D 60 EASEMeNr_ FARR 120 80 40 0 80 160 D LATERAL W m FUTURE LAVENDER HORIZONTAL SCALE IN FEET DRAINAGE AREA SW3 HEIGHTS SUBDIVISION 36,461 S.F./0.84 ACRE 1 EXISTING LAVENDER W � HEIGHTS SUBD.N0.2 Q DRAINAGE AREA 1 A DRAINAGE AREA 1 B �� Z 11,445 S.F. /0.26 ACRE 28,932 S.F./0.66 ACRE EXISTING LAVENDER r °T EXISTING LAVENDER �� 1 W HEIGHTS SUBD.NO.1 0 o HEIGHTS SUBD.NO.1 GIRR GIR,, 13 GIRR GIRR -EXIST. - III III WEG G ,-E�G- EG EG EG EG EG EG - - - EG _ EG EG EG EG EG EG PROJECT NO. 21-0216-LH3 G Ep E�C E� T- , P EP EP EP EP EP EP �E� SAWCUT SAWCUT SAWCUT SAWCUt SAWCUT SAWCUT E. LAKE HAZEL RD. SAWCUT �� SAWCUT SAWCUT - m lw� A W m AEU do �� MUNW-w r 1� m ft m i = � M 1�1 m � � � ff � m m = m m m m m ����arm m lw m arm = iwm f imaji/4 \ DWG FILE D.100 -SAWCUT SCUT SAWCUT SAWCUT SAWCUT S DRAINAGE AREA LAKE HAZEL SWALE DESIGNED BY BT 60,139 S.F. / 1.38 ACRE DRAWN BY JTA IMPERVIOUS = 31,864 S.F. CHECKED BY BT CITY OF MERIDIAN EXISTING LAVENDER ISSUE DATE 07/07/21 PARK SITE HEIGHTS SUBD.NO. 1 HORIZ.SCALE AS SHOWN VERT.SCALE AS SHOWN Dol 00 SHEET 1 OF 1 DACivil Innovations Projects\2021\21-0216-LH3 LAVENDER HEIGHTS NO.3\200-Construction Drawings\205-Construction\21-0216-LH3 D.100(Drainage Plan).dwg