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Home My WebLink AboutCity Hall ExpansionFontana City Hall Expansion Hydrology Report February 1, 2006 Pr FE IKE CONSULTING ENGINEERS Purpose Fontana City Hall lies between Sierra Avenue and Wheeler Avenue, north of Seville Avenue in central Fontana. The City of Fontana has plans to expand the existing City Hall to better serve the community. This expansion consists of two major components — a new 2 -story office building to the south of the existing City Hall and a parking structure in the east parking lot. This hydrology study shows the proposed hydrology after the both project aspects are complete. Description of Watershed This study looks at a 1.58 acre watershed that will be the site of the parking structure and the adjusted surface parking between the parking structure and City Hall. Currently this area surface drains along Wheeler Avenue and is collected in an underground storm drain system at the corner of Wheeler and Seville. As a result of this project, an additional catch basin will be added at the south end of the new parking garage. Both roof drains from the garage and flow from the new surface parking lot will drain to this catch basin. Ultimately, this water will flow to the same storm drain system. The proposed parking structure will be built over an existing road and parking lot. The permeable area will be slightly reduced in this part of the project. The surface parking will, however, result in an increase in permeable area — to 25%. The office building will not cause a change in the amount of permeable area in that portion of the project. The water from the office building site today surface drains across a parking lot. The proposed building will drain to the large landscape area south of the building. This portion will result in lower runoff and a longer time of concentration. Methodology The procedure described in Section D of the San Bernardino County Hydrology Manual, August 1986 edition, was used for the rational method analysis. City Hall Expansion Fontana February 1, 2006 Hydrology Study Page 1 Conclusion The proposed expansion to Fontana City Hall does not increase the peak stormwater flow. The peak flow as it enters the storm drain system will be reduced from 1.51 cfs to 1.48 cfs for a 10 -year storm event and reduced from 1.84 cfs to 1.82 cfs for a 25 -year storm event. There will not be an impact to the storm drain system as a result of this project. Table 1 below lists the calculated results. EXISTING CONDITIONS 10 year storm 25 ear storm Flow to storm drain 1.51 cfs I 1.84cfs PROPOSED CONDITIONS 10 year storm 25 year storm Flow to storm drain 1.48cfs 1.82cfs Table 1. Stormwater runoff, existing and proposed conditions. City Hall Expansion Hydrology Study Fontana Page 2 February 1, 2006 Client City of Fontana Designed by RL Date 2/1/06 Project City Hall Expansion Checked by MI Date 2/1/06 IKE Client City of Fontana Designed by RL Date 2/1/06 Project City Hall Expansion Checked by MI Date 2/1/06 IKE 3.5 3 2.5 W w U Z 0.4 = 2 F— a w 0 0.5 3.5 3 2.5 2 1.5 to 110*1 ::�± 0.5 0 0 2 5 10 25 50 100 RETURN PERIOD IN YEARS NOTE, 1. FOR INTERMEDIATE RETURN PERIODS PLOT 10 -YEAR AND 100 -YEAR ONE HOUR VALUES FROM MAPS, THEN CONNECT POINTS AND READ VALUE FOR DESIRED RETURN PERIOD. FOR EXAMPLE GIVEN 10 -YEAR ONE HOUR • 0.98" AND 100 -YEAR CNE HOUR ■ 1.60", 25 -YEAR ONE HOUR a 1.1 Go. REFERENCE IN0AA ATLAS 2, VOLUME 3I-CAL.,19T3 RAINFALL DEPTH VERSUS SAN BERNARDINO COUNTY RETURN PERIOD FOR HYDROLOGY MANUAL PARTIAL DURATION SERIES D-7 FIGURE 0-2 Curve (1) Numbers of Hydroloftic Soil -Cover Complexes For Pervious Areas -AMC a Cover Type (3) Quality of Cover (2) Soil roup 77 83 (Coniferous or broadleaf trees predominate. Fair NATURAL COVERS - 66 73 79 Canopy density is at least 30 percent.) Good Barren 33 78 86 91 93 (Rockland, eroded and graded land) 73 82 96 (Coniferous or broadleaf trees with canopy Fair Chaparral, Broadleaf Poor 33 70 80 83 (Manzonita, ceanothus and scrub oak) Fair 40 63 73 81 Good 31 37 71 78 Chaparral, Narrowleaf Poor 71 82 88 91 (Chamise and redshank) Fair 33 72 81 86 Grass, Annual or Perennial Poor 67 78 86 89 44 Fair 30 69 79 84 33 Good 38 61 74 80 Meadows or Cienegas Poor 63 77 83 88 (Areas with seasonally high water table, Fair 31 70 80 84 principal vegetation is sod forming grass) Good 30 38 71 78 Open Brush Poor 62 76 84 88 (Soft wood shrubs - buckwheat, sage, etc.) Fair 46 66 77 83 Good 41 63 73 81 - Woodland Poor 43 66 77 83 (Coniferous or broadleaf trees predominate. Fair 36 66 73 79 Canopy density is at least 30 percent.) Good 23 33 70 77 Woodland, Grass Poor 37 73 82 96 (Coniferous or broadleaf trees with canopy Fair 44 63 77 82 density from 20 to 30 percent) Good 33 38 72 79 URBAN COVERS - Residential or Commercial Landscaping Good �32 36 69 73 (Lawn, shrubs, etc.) Turf Poor 38 74 83 87 (Irrigated and mowed grass) Fair 44 63 77 82 Good 33 38 72 79 AGRICULTURAL COVERS - Fallow 77 86 91 94 (Land plowed but not tilled or seeded) SAN BERNARDINO COUNTY I CURVE NUMBERS FOR HYDROLOGY MANUAL PERVIOUS AREAS Figure C-3 0 of 2) mlowunmon dldliiaiiiiMM Ebb5 w///■//u■��■rr/■:�■ .:ssssss::s:::=aim: o �, 1 SZ AMC -r 600 50 O 500 1";9035 L=Sgo g 350 v OF300 c 250 t a 0 200 J c E c 0 ir 150 • P Develooment E f- 100 SAN BERNARDINO COUNTY HYDROLOGY MANUAL 25 Tc L 75- Mobil* Home 100 1000 17 90 900 H 80 600 14 TO 700 •i3 too r 60 600 50 O 500 1";9035 L=Sgo g 350 v OF300 c 250 t a 0 200 J c E c 0 ir 150 • P Develooment E f- 100 SAN BERNARDINO COUNTY HYDROLOGY MANUAL 25 Undeveloped Good Cover Undeveloped Fair Cover 2 SufuFq.ce LIMITATIONS, 75- Mobil* Home 1. Maximum length =1000 Feet 2, Maximum area = 10 Acres 17 ei v 16 H .. Y vSoo « $ 400 14 300 ca •i3 too N ~ 100 11 / — so op e0 10 �-- « 30 v >a to N - c Undeveloped Good Cover Undeveloped Fair Cover 2 Poor Cover (Min) 75- Mobil* Home 18 Single Family 17 (5-7 Du/AC) 16 20- Single Family -1 Acre Lot 15 C(Pavedla 14 e 13 (1) L= 550', H=5.do K- Single Family (5-7 Du/Ac) 12 `Z1 0 11 / D 10 Development, Tc=9.7 min. P,4 (' V-IN� Tc 5— 80- Apartment (Min) 75- Mobil* Home 6 65- Condominium 60- Single Family -59000 ft Z Lot 40 - Single Family -1 /4 Acre Lot 20- Single Family -1 Acre Lot 7 10 - Single Fatuity -21/2 Acre Lot e 5 (1) L= 550', H=5.do K- Single Family (5-7 Du/Ac) e 0 D 1� Qb* Development, Tc=9.7 min. B ! (I) 11 t 12 w 1; 13 _ •e �Ia 4 0Zl 15 s 16 7 18 '6 19 u - KE.Y. 20 L -H -Tc -K -Tc' w 25 9 80- Apartment 75- Mobil* Home c� 8 .�{ 65- Condominium 60- Single Family -59000 ft Z Lot 40 - Single Family -1 /4 Acre Lot 20- Single Family -1 Acre Lot 6 10 - Single Fatuity -21/2 Acre Lot SAMPLE 5 (1) L= 550', H=5.do K- Single Family (5-7 Du/Ac) Development, Tc=12.6 min. K- Comm (2) L= 550', He 5cIai 4 Development, Tc=9.7 min. 30 35 40 b. 0 E• c t N v c 0 t C 0 s w Figure D-1 D-4 8 c g 0 I1 2Eq, =. 0 600 06 50 0 d 500 ,8 33 0 400 30 350 ^j— 250 Jr z a 0 200 J F- 150 Zeis] c 23 LIMITATIONS PA4ZK-4n1 G- �7Tz'UC7V 24E i. Maximum length - 1000 Feet Tc L 5 100 1000 (MIN 90 900 H 80 6 800 400 TO o w 700 13 13 60 P. 8 c g 0 I1 2Eq, =. 0 600 06 50 0 d 500 ,8 33 0 400 30 350 ^j— 250 Jr z a 0 200 J F- 150 Zeis] c 23 LIMITATIONS PA4ZK-4n1 G- �7Tz'UC7V 24E i. Maximum length - 1000 Feet Tc 2. Maximum am - 10 Acres 5 w 5 (MIN r 16 H 6 X 400 14 -KEY � L -H -R -K -Tc' o w 300 13 13 oo 7 o N QQ~ Ia0 g out 6600 l�=8.Z8 cc v 30 9 O- Apartment 1'l) to 75- Mobile Home . o 10 t0 K 3, s 40 - Single Family -1/4 Acre Lot 35 tG 63 20 -Single Family -I Acre Lot tJ od od Cover 0 $ 3 2 12 llndewio to 13 Fair Cover 0 t ;� 14 _ .4 �- M 20 �Po" Coo�ver o l'Z� IS • 19 m 16 5 is 17 Single s- i ou/ac e Famn 16 18 15 Cpierclol� (Paves) 'moi, 19 14 -KEY � L -H -R -K -Tc' 0 20- 13 13 c 12 � 25- 5 10 10 Development 9 O- Apartment o 75- Mobile Home 30 13 65- Condominium•EE 60- Single Family -59000 ft2 Lot F 40 - Single Family -1/4 Acre Lot 35 tG 63 20 -Single Family -I Acre Lot 6 10 -Single Family -21/2 Acre Lot 40 EXAMPLE= 5 (1) L x 55d, H- 5.d, K+ SM910 FaWly (5-7 DU/AC) Development, Tc=12.6 min. (2) L- 550', H- 5.01, K- Commercial 4 Development, Tc -9.7 min. SAN BERNARDINO COUNTY HYDROLOGY MANUAL Figure D-1 D-4