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Home My WebLink AboutCOM 0306.003 2006-2008 rir or ~'~y Edwin S Tatra Harry Kim Ma or Housrng dAwnnsrrtnor y of Sri p~'N~:P ~ountp of ~atuaii OFFICE OF HOUSING AND COMMUNITY DEVELOPMENT i0 Wailuku Drive • Hilo, Hawaii 96720-?456 V/1 f (808) 961-8379 • FAX (808) 961-8685 July 3, 2007 Susan Fischer Keanahalululu LLC. P.O. Box 44417 Kawaihae, Hawaii 96743 SUBJECT: Keanahalululu LLC. Affordable Housing Condition TMK: 5-9-007:007 Pursuant to your telephone request of June 18, 2007, the Office of Housing and Community Development (OHCD) has consulted with Christopher J. Yuen, Planning Director, and determined that the affordable housing requirement for the above-referenced Kohala subdivision shall have a condition of satisfying one (1) affordable housing credit. If you have questions or need additional information, please call us at 961-8379. Thank you. Edwin S. Taira Housing Administrator ~om~ No. 30.3 Ref. To: ?~eh w Ref. Dote 1362pasr EQUAL HOUSING OPPORTUNITY 'HAWAI'I GDUNTV IS AN EDUAL OPPORTUNITY PROVIDER AND EMPLOYER" CONTINUED ABOVE j I , ~ l/il~~l~ ~ ~ ~ ~ ~ i ~ _ . s ~ i i I ~ ii i ~ .I~l~ lilt i~'~ - ~ ~ ~ ~ \,\A~~A ~i' ~ 1 \ _ _ i ' i i i 1 1 VA ~1 ~i, ~~~~i~~il~il~l~l~llll~l',~w~ 161 ,1 ~~~~VA~,~~~~~~ I I 1 \ i i i ' 1 \ ~ \ ' 1 I v' 111 I'I'' ~;i ~ ~ ~ ' ~ ~ I ~ i . ,i i i I ~ i t ~ ~1 ~•vA ~ A v ~ 1 Ili ~ ~ ~ ~-.v ` V 'V~~~ ul~ ~'~V ~ I'. 1d1d \ i 'i ~ '~~v~ ~~~~AA~~ .~IA~ _ \ VA~ g \ ~ - ' ~ ' x`11 \ ~ ~ _ ~ ~ ~ - ~ 1 - _ - - l I ' ~ \ ~ III \ % ~ ~ ~ I ~ I \ %s'Rgr 1 I ,~j ~,~l l ~ ~ ~ ~a iiil ~ ~ l \ ,V A A mil= ~ ~ , _ ` ` ` . ~ y „i ~ i~ ~ r ~ ~ IO - / ~ 1'r~ ~ ~ / VIII li i II ~I rl I i i lc CONTINUED BELOW m W ~ ..,v.. ~ ~ °~mOX' Keanahalululu e`+x^^+~ Subid~ision of Lot 14 w.. x' R SAS ~ K hp0 E fOtee BNpfN88RIN0 O - GRADING PLAN a TRIAD ENGINEERING 440 w. Benson Blvd.. Suite tt 206 telephone 907-561-6537 P.O. BOX 110890 Fax 907-561-6869 Anchorage. Algskq 9951 I-0890 a-moil: davegrenier@lonlechi.com July 9. 2007 Count)' of Hawaii Public Works Engineering 75-5706 Kuakini Hwy., Suite 107 Kailua-Kona, Hawaii 96740 Subject: Keanahalululu Subdivision; Updated Drainage Calculations TMK's: (3) 5-9-07: Folder No. 5941 The following report updates the previous drainage calculations dated 7-21-95 for the proposed Keanahalululu Subdivision. The project consists of 8 residential lots on approximately 29 acres and will have paved roads and driveways along with water service provided by Kohala Ranch Water Company. This report compares the before development condition to the afrer full development condition. The difference between the two reports is that drainage basins are now proposed to handle the on site drainage rather than 8 K sumps as previously shown on the construction plans. The attached drainage plan shows the proposed drainage basin locations. The Rational Method with a 10 year recurrence interval was used in determining the anticipated flows from the drantage basins with non-paved & paved azeas calculated separately and then combined for a total figure. The drainage ways I'or [he mauka off site runoff originating from Easement 820 & 82 ] will not altered or disnrrbed with the exception road crossings. The following calculations assume 714 sf/cfs of infiltration for the drainage basins, as recommended by the County for similar- projects. This value is conservative based upon the assumption that siltation and poor maintenance of the basins will be the nornt rather than the exception. PROJECT DRAINAGE BASIN: o Present Condition: Area: 28.83 ac; Length: 550 If; Av. Slope: 8%Ave; Tm (10 yr): LS Per Plate 3 Tc: 15 min Per Plate 4 1: 2.7 C: ]nfiltration 0.07 (medium) Relict 0.06 (hilly) Cover 0.0~ (poor) Develop. "Type 0.15 (Ag.) 0.33 Q =CIA =(0.33)(2.7)(28.83) = 25.7 cfs I of5 DRAINAGB BASIN 1: o Present Condition: Area: 2.56 ac; Length: 370 If; Av. Slope: 5°i~ Ave: Tm (10 yr): 1.5 lime of Concentration: Per Plate 3 Tc: 14 min Per Plate 4 I: 2.8 C: Infiltration 0.07 (medium) Relief 0.06 (hilly) Cover 0.05 (poor) Develop. Type 0.15 (Ag.) 0.33 Q =CIA =(0.33)(2.8>(2.56) = 2.36 cfs o After Development: Unpaved Area: 2.1 ac: Length: 370 lf; Av. Slope: Tm (10 yr): 1.5 Time of Concentration: Per Plate 3 'I~c of 14 min: Per Plate 4 is 2.8 C: Infiltration 0.07 (medium) Relief 0.06 (hilly) Cover 0.05 (poor) Develop, Type 0.15 (Ag.} 0.33 Q =CIA =(033)(2.8)(2.1) = 1.94 cfs Paved Area: 0.46 ac: (20' paved road 0.26 ac; houses & drives 0? ac) Length: 400 lf; Av. Slope: 1%: Tm (10 yr): 1.5 Time of Concentration: Per Plate 3 '['c of 8 min Per Plate 4 I: 3.3 C: L~Itration: 0.95 For Pavement Q =CIA =(0.95)(3.3)(0.46) = 1.44 cfs Drainage Basin 1 Smnmary: After Development: 1.94 + 1.44 = 3.38 cfs Before & After Development Difference: 3.38 - 2.36 = 1.02 cfs Basin No. l Capacity: 3,200 cf; Surface Area Available for Infiltration: 1.600 sf. Using an Infiltration Rate of 714 sf per cfs (I "/min), Basin No. 1 capable of 2?4 cfs. DRAINAG)C BASIN 2: o Present Condition: Area: 6.92 ac; Length: 460 lf; Av. Slope: 17% Ave: Tm (10 yr): I S Time of Concentration: Per Plate 3 Tc: 12 min Per Plate 4 I: 2.9 C: Infiltration 0.07 (medium) Relief 0.06 (hilly) Cover 0.05 (poor) Develop.'I'ype 0.15 (Ag.) 0.33 Q =CIA =(033)(2.9)(6.92) = 6.62 cfs o After DevelopmenL• Unpaved Area: 6.50 ac; Length: 4601f; Av. Slope: I7%; Tm (l0 yr): L~ Time of Concentration: Per Plate 3 Tc of 12 min: Per Plate 4 I: 2.9 C: Infiltration 0.07 (medium) Relief 0.06 (hilly) Cover 0.05 (poor) Develop. Type 0.15 (Ag.) 0.33 Q =CIA =(0.33)(2.9)(6.50) = 6.22 cfs Paved Area: 0.42 ac: (20' paved road 0.42 ac; no houses or drives) Length: 540 lf; Av. Slope: 5%: Tm (10 yr): 1.~ "Time of Concentration: Per Plate 3 Tc of 6 min Per Plate 4 I: 3.9 C: Infiltration: 0.95 For Pavement Q =CIA =(0.90(3.9)(0.42) = 1 S6 cfs Drainage Basin 2 Summary: After Development: 6.22 + 1.56 = 7.78 cfs Before & After Development Difference: 7.78 - 6.62 = 1.16 cfs Basin No. 1 Capacity: 2,900 cf; Surface Area Available for Infiltration: 1,450 sf. Using an Infiltration Rate of 714 sf per cfs (I"/min), Basin No. 1 capable of 2.03 cfs. DRAINAGE BASIN 3: o Present Condition: Area: 2.99 ac; Length: 600 If; Av. Slope: l0% Ave; Tm (10 yr}: 1.5 Time of Concentration: Per Plate 3 Tc: 15 min Per Plate 4 I: 2.7 C: Infiltration 0.07 (medium) Relief 0.06 (hilly) Cover 0.05 (poor) Develop. Type 0.15 (Ag.) 0.33 Q =CIA =(0.33)(2.7)(2.99) = 2.66 cts o After Development: Unpaved Area: 2.60 ac; Length: 600 lf; Av. Slope: 10%; '1'm (10 yr): 1.5 Time of Concentration: Per Plate 3 Tc of 15 min: Per Plate 4 L 2.7 C: Infiltration 0.07 (medium) Relief 0.06 (hilly) Cover 0.05 (poor) Develop. Type 0.20 (Ag.) 033 Q =CIA =(0.33)(2.7)(2.60) = 2.32 cfs Paved Area: 0.39 ac: (20' paved road 0.19 ac; houses & drives 0.2 ac) Length: 300 li; Av. Slope: 5%: Tm (10 yr): 1.5 Time of Concentration: Per Plate 3 Tc of 5 min Per Plate 4 I: 3.9 C: Infiltration: 095 For Pavement Q =CIA =(0.95)(3.9)(0.39) = 1.44 cfs Drainage Basin 3 Summary: After Development: 2.32 + 1.44 = 3.76 cfs Before & After Development Difference: 3.76 - 2.66 = 1.10 cfs Basin No. 1 Capacity: 5.000 cf; Surface Area Available for Infiltration: 2,500 sf. Using an Infiltration Rate of 714 sf per cfs (I"/min), Basin No. 1 capable of 3.5 cfs. DRAINAGE BASIN 4: o Present Condition: Area: 2.66 ac; Length: 4901f; Av. Slope: 18% Ave; Tm (10 yr): 1.5 Time of Concentration: Per Plate 3 Tc: 12 min Per Plate 4 I: 2.9 C: Infiltration 0.07 (meditun) Relief 0.06 (frilly) Cover 0.05 (poor) Develop. Type 0.15 (Ag.) 0.33 Q =CIA =(0.33)(2.9)(2.66) = 2.55 cfs o After Development: Unpaved Area: 23 ac; Length: 490 lf; Av. Slope: 18%; Tm (10 yr): I S Time of Concentration: Per Plate 3 Tc of 12 min: Per Plate 4 I: 2.9 C: Infiltration 0.07 (medium) Relief 0.06 (frilly) Cover 0.05 (poor) Develop. Type 0.20 (Ag.) 0.33 Q =CIA =(0.33)(2.9)(2.30) = 2.20 cfs Paved Area: 0.36 ac: (20' paved road 0160 ac; houses & drives 0? ac) Length: 320 (f; Av. Slope: 13%: Tm (10 yr): 1.> Time of Concentration: Per Plate 3 Tc of 5 min Per Plate 4 1: 3.9 C: hrfiltzation: 0.95 For Pavement Q =CIA =(0.95)(3.9)(0.36) = 1.33 cfs Drainage Basin 4 Summary: After Development: 2.20 + 1.33 = 3.53 cfs Before & After Development Difference: 3.53 - 2.55 = 0.98 cf's Basin No. 1 Capacity: 2,000 cF, Surface Area Available for Infiltration: 1,000 sf. Using an Infiltration Rate of 714 sf per cfs (1 "lmin), Basin No- 1 capable of 1.4 cfs. 5umma~y~: The proposed drainage basins are capable of handling a mitumum of 9.17 cts, compared with the increase of 4.26 cfs due to the development. _ Submitted By: ~;~'~tj?, ,?Qr ~,'r David A. Grenier, P.E. ~'~:~YT., T, ~`l~V °~yry,r ~ € 6 1.%r~~~.~-_ir I • v m '-r-"-_ ,~,,1 , ~r c~c o , - . = ,~\J . ~ J 7~11~~~/ ~~Ir I(' ~I~(l ~l ~ 1~~~~: ~\1 i . 1.. ~ y ~u ~ z ~ ~ =a _ ~ \ ! Q Q J \ / C 2 ~ ~ ~ O K 1' ~ N O ~ ' / Y ~r'(A . „T., n sf i ~ ~ is \ ~ ~ T. ti o ~ . ~ > _ J_~" eb _ _