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Home My WebLink AboutTHE GATES AT WOODRIDGE PUD, 3RD FILING - FINAL - 55-87H - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORT ! ® • I FINAL DRAINAGE AND EROSION CONTROL STUDY FOR THE THE GATES AT WOODRIDGE THIRD FILING FORT COLLINS, COLORADO I October 26, 1992 I 1 Prepared for: Woodcraft Homes 111 1501 N. Cleveland Avenue Loveland, Colorado 80538 Prepared by: RBD, Inc. Engineering Consultants 2900 South College Avenue 1 • Fort Collins, Colorado 80525 (303) 226-4955 1 RBD Job No. 434-008 I 1 ® • 930NC. ' Engineering Consultants • 2900 South College Avenue Fort Collins,Colorado 80525 ' 303/226-4955 FAX:303/226-4971 October 26, 1992 Ms. Kathy Malers City of Fort Collins Utility Services Stormwater 235 Mathews Street Fort Collins, Colorado 80522 RE: Final Drainage and Erosion Control Study The Gates at Woodridge Third Filing Dear Kathy: We arepleased to submit to you, foryour review and approval, this Final Drainage and PP � g Erosion Control Study for the Gates at Woodridge Third Filing. All computations within this report have been completed in compliance with the City of Fort Collins Storm Drainage Design Criteria ' We appreciate your time and consideration in reviewing this submittal. Please call if you have any questions. Respectfully, RBD Inc. Engineering Consultants (742r.a.)e Roger Curtiss, P.E. Project Engineer 1 cc: Mr. Gary Berger Mr. John Hutchinson 1 Other offices:Denver 303/458-5526•Vail 303/476-6.340•Longmont 303/678-9584 I ITABLE OF CONTENTS IDESCRIPTION PAGE I. GENERAL LOCATION AND DESCRIPTION 1 I A. LOCATION 1 B. DESCRIPTION OF PROPERTY 1 I II. DRAINAGE BASINS 1 A. MAJOR BASIN DESCRIPTION 1 I III. DRAINAGE DESIGN CRITERIA 2 A. REGULATIONS 2 B. DEVELOPMENT CRITERIA REFERENCE AND CONSTRAINTS 2 IC. HYDROLOGICAL CRITERIA 2 D. HYDRAULIC CRITERIA 2 E. VARIANCES FROM CRITERIA 2 1 IV. DRAINAGE FACILITY DESIGN 3 A. GENERAL CONCEPT 3 IB. SPECIFIC DETAILS 3 V. EROSION CONTROL 4 IA. GENERAL CONCEPT 4 B. SPECIFIC DETAILS 4 IVI. CONCLUSIONS 5 A. COMPLIANCE WITH STANDARDS 5 B. DRAINAGE CONCEPT 5 I' C. EROSION CONTROL CONCEPT 5 1 REFERENCES 6 APPENDIX IVICINITY MAP 2 DETENTION 3 I THIRD FILING HYDROLOGY 5 DESIGN OF CHANNELS, SWALES 8 EROSION CONTROL 10 ICHARTS, FIGURES AND TABLES 14 I I I 1 FINAL DRAINAGE AND EROSION CONTROL STUDY FOR THE GATES AT WOODRIDGE THIRD FILING FORT COLLINS, COLORADO 1 I. GENERAL LOCATION AND DESCRIPTION A. Location The Gates at Woodridge P.U.D. is bounded by Future Harmony Road on the west, open space (future filings) and Imperial Estates on the north, Webber Junior High School and Regency Park PUD to the east and by the Gates Second Filing and existing Harmony Road on the south. The site location can also be described as situate in the Southwest 1/4 of Section 34, Township 7 North, Range 69 West of the 6th P.M., City of Fort 1 Collins, Larimer County, Colorado. The site location can be seen on Exhibit 1 in the appendix. B. Description of Property The Third Filing of the Gates at Woodridge contains approximately 5.0 acres, more or less. Presently, the property is undeveloped. The property is being proposed for planned unit development within the City of Fort Collins Zoning District PUD, and will be developed consistent with the Gates First and Second Filing at Woodridge. Native grasses presently cover the property. The topography of the site generally slopes from west to east at approximately 1.5 percent. 1 II. DRAINAGE BASINS 1 A. Major Basin Description The proposed development lies within Basin 80 of the McClellands and Mail Creek Major Drainageway Plan prepared by Cornell Consulting Company. A natural drainageway runs from west to east along the northern edge of the project boundary within Basin 80. Runoff from Basin 80 is routed by open channels and culverts along the northern boundary of the First and Second Filings of The Gates, along the north side of Seneca Street past Webber Junior High School and then along the east side of Regency Drive to the existing Regional Detention Pond. 1 1 1 1 11110 III. DRAINAGE DESIGN CRITERIA A. Regulations The City of Fort Collins Storm Drainage Design Criteria is being used for the subject site. B. Development Criteria Reference and Constraints From the Preliminary Drainage Report for the 1990 Junior High School, the channel and culvert system along the north side of Seneca Street and the 1 east side of Regency Drive was sized for undetained off-site 100 year developed runoff from Basins 79, 80, and 85. A current SWMM model analysis for Basins 79 and 80, obtained by the City of Fort Collins, has determined that the existing channel, culverts and Seneca Street (downstream of the subject site) will receive greater 100 year developed runoff than was originally anticipated. The City of Fort Collins is currently reviewing this matter and has indicated that the downstream existing improvements may not be adequate to transport the entire 100 year developed runoff (318 cfs) that could be produced from the Woodridge property at Seneca Street and the East property line. The City is considering acquiring a portion of the Woodridge property for use as an additional regional detention pond. C. Hydrological Criteria The Rational Method for determining surface runoff was used for the project site. The 2 year and 100 year storm event criteria, obtained by the City of Fort Collins, was used in calculating runoff values. These calculations and criteria are included in the Appendix of this report. D. Hydraulic Criteria All hydraulic calculations within this report have been prepared in accordance with the City of Fort Collins Drainage Criteria and are also included in the Appendix. E. Variances from Criteria No variances are being sought for the proposed project site. i I 1 2 I 1 IV. DRAINAGE FACILITY DESIGN A. General Concept All on-site runoff produced by the proposed development of the Gates at Woodridge Third Filing will flow easterly to the existing drainageway along the east side of Seneca Street and eventually arrive at the Regional Detention Pond. Included in the back pocket of this report are the proposed drainage and grading plans. B. Specific Details The Gates at Woodridge Third Filing has been broken down into three subbasins; 18A, 18B, and 19. These subbasin designations correspond to the basin designations of the Preliminary/Master Drainage Study for the Woodridge development. Runoff from basins 18A and 18B will be directed to Silvergate Road and will travel easterly to curb inlets placed on either side of street at the intersection of Overlook Drive and Silvergate Road in the Gates Second Filing. Flows from these curb inlets is piped to the north to the Regional Channel and on to the existing drainageway at Seneca Street. The curb inlets were sized in the Second Filing Drainage Study to accommodate all of basin 18 as described in the Preliminary/Master Report for Woodridge, and also have been sized to accommodate 100 year flows (37.5 cfs) with an emergency overflow path north through an opening between lots 2 and 3. Runoff from Basin 19 will be directly overland to the Regional Channel. A portion of the regional channel has been constructed with the First and Second Filings of the Gates, up to a point just to the east of an existing Fort Collins - Loveland Water District water line. This project will require the lowering of that existing water main, and the completion of the interim fully developed regional channel up to Future Harmony Road. Storm water runoff collected in the regional channel will be directed easterly to the existing 42 inch culverts immediately north of Seneca Street. There flows travel via open channels and additional 42 inch culverts to the Regional Detention Pond at Wake Robin Lane and Regency Drive. The City of Fort Collins is currently studying the possibility of reconfiguring the two existing 42 inch culverts to provide a more efficient transmission of storm water to the east. 3 I I The existing downstream culverts, open channels and streets have the available capacity for the Gates at Woodridge Third Filing V. EROSION CONTROL A. General Concept This development lies within the High Rainfall Erodibility Zone and the Moderate Wind Erodibility Zone per the City of Fort Collins zone maps. The potential exists for moderate erosion problems after completion of the Third Filing improvements, due to some existing and proposed site slopes of greater than 2%. It is also anticipated that the project site improvements will be subject to both wind and rainfall erosion before new vegetation can take hold or before the new residential lots are developed. The Erosion os on Control Performance Standard (PS) for this project was computed to be 80% per the criteria in the City of Fort Collins Erosion Control Reference Manual for Construction sites. The Effectiveness (EEF) of the proposed erosion control plan was calculated to be 81%. Therefore, the erosion control plan below meets the City of Fort Collins' requirements. A copy of the calculations has been included in the appendix. 111 B. Specific Details After the overlot grading has been completed, all disturbed areas, not in a roadway, should have temporary vegetation seed applied. After seeding, a hay or straw mulch should be applied over the seed at a rate of 2 tons/acre minimum, and the mulch should be adequately anchored, tacked, or crimped into the soil. After the utilities have been installed, the roadway surfaces should receive the pavement structure. If the disturbed areas will not be built upon within one growing season, a permanent seed should be applied. After seeding, a hay or straw mulch should be applied over the seed at a rate of 2 tons/acre minimum, and the mulch should be adequately anchored, tacked or crimped into the soil. In the event a portion of the roadway pavement surface and utilities will not be constructed for an extended period of time after overlot grading, a temporary vegetation seed and mulch should also be applied to the roadway areas as discussed above. I 1 4 I I ® VI. CONCLUSIONS A. Compliance with Standards All computations that have been completed within this report are in compliance with the City of Fort Collins Erosion Control Reference Manual for Construction Sites and the Storm Drainage Design Criteria Manual. In addition, all computations are in compliance with the Preliminary/Master Drainage Study for Woodridge prepared by RBD, Inc. in December 1991. B. Drainage Concept The proposed drainage concepts adequately provide for the transmission of developed on-site runoff to the existing drainage devices at the eastern property line of the subject site. The existing storm sewer system installed in the Second Filing of the Gates will collect the 100 year developed flows generated by basins 18A and 18B, and discharge into the proposed regional channel. Basin 19 will discharge directly into the proposed regional channel. The 100 year runoff generated by development of this site will be carried to the existing off-site regional detention pond by a series of existing culverts, open channels and streets per the Preliminary/Master Drainage Study for Woodridge. The City of Fort Collins is currently studying the possible reconfiguration of the existing 42 inch culverts at Webber Junior High School adjacent to Seneca Street. Depending on the outcome of this analysis, the existing culverts may or may not be reconfigured for this development. In addition to the 42 inch culvert study, the City of Fort Collins is also evaluating the capacity of downstream improvements in regards to the new SWMM runoff flows which exceed the previously used downstream criteria. For the Gates Third Filing, adequate downstream capacity in the culverts, open channels, and street systems exists to safely convey developed runoff to the Regional Detention Pond east of Regency Drive. At the time of construction, if for some unforeseen reason groundwater is encountered during construction, a Colorado Department of Health Construction Dewatering Permit would be required. C. Erosion Control Concepts The proposed erosion control concepts adequately provide for the control of wind and rainfall erosion from the Gates Third Filing. Through the construction of the proposed erosion control concepts, the City of Fort Collins performance standards will be met. The proposed erosion control 111 5 1 1 concepts presented in this report and shown on the erosion control plan are in compliance with the City of Fort Collins erosion control criteria. REFERENCES 1. Storm Drainage Design Criteria and Construction Standards by the City of Fort Collins, Colorado, May 1984. 2. Erosion Control Reference Manual for Construction Sites by the City of Fort Collins, Colorado, January 1991. 3. Preliminary/Master Drainage Study for Woodridge by RBD, Inc. Engineering Consultants, December 27, 1991. 4. Final Drainage and Erosion Control Study for the Gates at Woodridge Second Filing and the Overlook at Woodridge Second Filing, by RBD, Inc. Engineering Consultants, March 3, 1992. 5. The McClellands and Mail Creek Major Drainageway Plan byCornell Consulting 9 Y Company, December 1980. 6. The Final Drainage Report for Regency Park PUD byParsons and Associates 9 p g Y Consulting Engineers, March 30, 1987. 7. Preliminary Drainage Report for the 1990 Junior High School by RBD, Inc. Engineering Consultants, February 5, 1988. 8. Final Drainage Report for Poudre School District R-1 Elementary School by Engineering Professionals, Inc. April 1987. • I I 1 I 1 6 1 1 APPENDIX 1 1 1 1 1 1 1 1 1 i 1 1 1 / • :* .1 , • 1 - :! : :1 '..: %) ed, 1 • ,; ;NI •,,,• i il .'• /11:i .:‘'. ..ye!,1.1;:........,...:, ... • , II : ,7..,, ...,.:// 'N }..•,..\.„.:,. 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U 1,-, _. _ _ I CC U 0 a c oo w \ U �, cJ ,- N O N N o Q Z 0 �. 0 0 0 0 0 ° W ( z u. ti M — 01 F- I tom- w } �� c°Ci 2 Z m E' O 0 0 � J m 0 Q 0 W^ W N e\ p\ X n\ U -- cn a w N N t� Ni N Nz Ux m N - I—}-- IG -- 0 lU 0 0 1) 0 Z N a O. - 3 t o 3 i s a M z t3 Q (� 0 0 p 0 ca _n p Q . . Q Q a M o aN c� o z (/� mQ wQy 0 r o r o mod 0 0 c� U O 0 I - 02 d Iav-s 1-, 2 a'v-).-, \ . • • • • • • • E o if) i N N . t o= tl` . 0 • • •0 1 •tl] • ,� Sd j. N 6- 0 1 X00010A N r . Q. —u6!sop N - — • Q 1- sd, of 1 < 4- xn30ID/� N 1 o el r S;D O, Q N u613DQ — + • �`�l 0 S;D oD j I W XI,I3DdDO — 1 0 0 • 11 Q • N aZiS tfi o 0.0 • \. t .. al wi CC .0 < • co DdoIS — Z s1.2 tit 2 clDDdoo to - olgoMolidF _ _ J W "' cr. 0 CCado�S "i ' C..+ of p q `- v s3o 3}ouna 4. N M 0;. NuoilDwwns m 0 Ni di }-- j.louna N� .. a logio s;D i N i d N noun a =I M 0 o N loD�1p co ti-j W DODO ndr, 0 2; I p 1� . 3 1 0 DDJ d r'd a a m o Xosuzluj N N N j O . II ict �'• �. no.. d 0 1 1ualo!UUDo3 d 0 6 A o 4 •uiw ._. r _a, _ r uo!1D.11uOouo3 r- m r X 10 Oulu a0 _ r �, •uiw Q� � Ddid I r •u1w gIODJs w)� uiw • owl.L 131u1 y16ua- 1. d d d d m Su1SDg N ' -A 03 Q\ d) 0 O I c 1O d_ o g • • J N i 0 1 I 1 r DESIGN OF CHANNELS, SWALES 1 I 1' I ■ I 1 1 1 I 1 1 ■ I ® • '42. I II RBD INC. ENGINEERING CONSULTANTS CHANNEL RATING INFORMATION INTERIM REGIONAL CHANNEL FULLY DEVELOPED CONDITION EAST OF HARMONY ROAD 11 STA ELEV Q Z.-=...._5 ..9---C 5..... .. . 1 0.00 20.00 - 20.00 15.00 (i oc . = 0.14-.l0 c.+-S 26.00 15.00 46.00 20.00 'N' VALUE SLOPE (ft/ft) I 0.035 0.0060 ELEVATION AREA VELOCITY DISCHARGE FROUDE (feet) (sq ft) (fps) (cfs,) NO. I 15.50 4.0 1.8 7.11 0.50 II 16.00 10.0 2.6 26.05 0.54 z= S-T.9 La ci = t, . S I 16.50 18.0 3.3 58.56 0.57 17.00 28.0 3.8 106.83 0.60. 17.50 40.0 4.3 173.02 0.61 Qloo = 2:-.I4.(o 42. G = Z.7' II 18.00 54.0 4.8 259.16 0.63 18.50 70.0 5.2 367.22 0.64 19.00 88.0 5.7 499.07 0.66 19.50 108.0 6.1 656.54 0.67 I 20.00 130.0 6.5 841.37 0.68 I I • I 7V' m cZ - 1 • 5' Via' e � EROSION CONTROL I ® ® It zz IRAINFALL PERFORMANCE STANDARD EVALUATION PROJECT: - STANDARD FORM A 1 COMPLETED BY: a-C e ss (IZ at7, - DATE: a3 9a DEVELOPED ERODIBILITY Asb Lsb Ssb Lb Sb PS ISUBBAMIN ZONE (ac) (ft) (%) (feet) (%) (%) Ilrc>14_Qn,kiFa. I --_-.. ),L3_A__._..._.. MO.D.E2ATE lU.i L10 _._.3.03._ . _-_(zz,-7 c..) _ _.__.Z._/ LZ._. _.._ ----c,,-2___ 1 Q:S _�� . l . I �b. - SuKA (.__LS[ .. ,kSb)-,/ U_M- _..L.Sb_. _ ED ' L.)N.A ( `..,S1_. 4i.e- A-S6) 7SL)%n 11-si:, _ _ I . _. L1„ _= C3.t> 0:::7-7 ( ,-7t] 4 5> r (0<4?�3 { tv ) I S6 _ (a_._(:)_3")(-7_"/� -r (Di.-7s Zf) -3-(e_9eXo-8)__- 1 4. fib_..__ .__ 1o.-7s%_ _ I12_o_nrl - ns__.- 8U o I I I MARCH 1991 8-14 DESIGN CRITERIA II zAz IEFFECTIVENESS CALCULATIONS PROJECT: oT� e- W Gc pJ>Y ..rc� �t�IN� STANDARD FORM. B ICOMPLETED BY: .S. G_U1;TIss 'ado, I *,c... DATE: LCS• z39Z Erosion Control C-Factor P-Factor Method Value Value Comment . I .Ro A --P0v e.D _If.,.GO_N._STY-L3CT_ED_ .?...,,2A.1,/St_.--1=t t_T- _2S.- 1 , coo . C) ,.80 _._I_t.I.LET_S I •• •,...r eAN.1...t—e-_,A.1._ff...s __ -14y__._Qe._STPuv iMULL+t ----------- - - -- I W/.1-EMP.__.5.=SD C]_..00., I,,,.O.- .. ....Li_ P.cn=-._..T..10T hd..-I - I .. - — - ------ -- z oo �+./oy. - MAJOR PS SUB AREA BASIN (%) 'BASIN (Ac) CALCULATIONS I r' o /- -- .- I t-1 .1.1 u-r._ICI T->_.__ PwK.1 _tS .TC, USE __::t._ r-n:P_,_S.EE-.._.-'�4--.n'tLx.CH ._. Al- DISTu.Q-ESED._.. . 1 .ArQ EoS N OT I tJ A-• P f>..n�'- ' 4 us ST2... y..i e7.1c..La.S. I767-pc_ 1STUP ; .O LDS - 4.-72_ .oc,_ I vMJ= 24DnS NOT !-C)$..IS �., Ll-/I:-n4-1L fo_ .V./1=E lLS - --- - I • __. . - (I - C 41 in)( I c.o.') __ _ 1_ (Os_ )o.ap31ha.___ - .. - _-C__ - 19Z X c -J - - 3.1 D:� I 1 IMARCH 1991 8-15 DESIGN CRITERIA • 13/ i IIIzz ' 1 CONSTRUCTION SEQUENCE 1 PROJECT: (/' b1 r1=S ,1/oop2_1 11:>C, rd '-t u sLC_ STANDARD FORM C I SEQUENCE FOR 19 93 ONLY COMPLETED BY: 3. ( i )�ns5 DATE: C.cr. Z3 , 19,Z L3 eD, hue_ Indicate by use of a bar line or symbols when erosion control measures will be installed. Major modifications to an approved schedule may require submitting a new schedule for approval by the City Engineer. 11 1993 YEAR 1` MONTH I I I J IF I >uI 111.E I J I I I OVERLOT GRADING 1 l WIND EROSION CONTROL Soil Roughening Perimeter Barrier 1 Additional Barriers • Vegetative Methods Soil Sealant • II Other EROSION CONTROL IRAINL STRUCTURAL: _ Sediment Trap/Basin Inlet Filters II Straw Barriers Silt Fence Barriers Sand Bags II Bare Soil Preparation Contour Furrows Terracing Asphalt/Concrete Paving I/ Other II VEGETATIVE: j Permanent Seed Planting Mulching/Sealant II Temporary Seed Planting ! Sod Installation • Nettings/Mats/Blankets Other I• l "STRUCTURES: INSTALLED BY MAINTAINED BY VEGETATION/MULCHING CONTRACTOR DATE SUBMITTED APPROVED BY CITY OF FORT COLLINS ON I 11 MARCH 1991 8-16 DESIGN CRITERIA I 4�Zz 1 • • 1 1 1 1 CHARTS, TABLES AND FIGURES 1 1 I I I 1 I p I I I ® ® ZZ DRAINAGE CRITERIA MANUAL RUNOFF 1 • 1 1 50 30 IIIII lirII . • I t . 20 0 2 0 * W �e o. • r �ry 4 h. * ti . CC J LU y .ate 0Air V. 4 . o. 10• . �4, UJv o �i Lau" rw 41 �v /°e a �32. � ys' ice■ I II I HI ' 24 i yvt4°1 cc �~3 / 4?/ 111111 . / 4 A1®11 1 v. AIMIMMIMMII w �y Q iZr i ' I .1 .2 .3 ,5 1 2 3 5 10 20 VELOCITY IN FEET PER SECOND • FIGURE 3-2. ESTIMATE OF AVERAGE FLOW VELOCITY FOR , IUSE WITH THE RATIONAL FORMULA. ' I * MOST FREQUENTLY OCCURRING "UNDEVELOPED'•' LAND SURFACES IN THE DENVER REGION. REFERENCE: "Urban Hydrology For Small Watersheds" Technical Release No. 55, USDA, SCS Jan. 1975. • 5-1-84 • IURBAN DRAINAGE & FLOOD CONTROL DISTRICT ' ® 16/ I ® zz . • I 0 as 0 0 �w �0 ° 1- . 1! • _ _..J - U •F-- IL cc _-- _ _ _ ■ - _. : _ N .v , -_—__ - r p _ _� `n WZoo _ _ ■ -- PI-- 2 cr o J - --____ _-- - ae _ a i a�i O W a2.6 U - _ ____ _ 2 0 W 1 �- --- --- m oo.� , — N V► El - --- ■ �- cr z W QI 3 __ ___ C1 Q N -- -- -. 0 Ili > wx -- _ ■ �. f J W oQo ' _ 1 / a MI CO Y -- Film 0 cr 1 0z _ -- _ - : ill Z _ - __-- ; - 17 ■- -...< 4:t. fli Lill _- i . h_1 Iiiii f 1...._ GP ___ ____ ___111_•• 411. ° JO I i , _____L_ pd il • gi ? il i . -_-- • —1 ... 0 ----- -- - --- -----N -- - ti (D in 0 IJ1iOH 133d S3HONI —NOLLVIld103»d • IMAY 1904 3-2 DESIGN CRITERIA 17/ I ill ® zZ Calculations for Curb Capacities and Velocities III Major and Minor Storms il per City of Fort Collins Storm Drainage Design Criteria ll RESIDENTIAL with drive over curb and gutter Prepared by: RBD, Inc. a is for one side of the road only February 28, 1992 V is based on theoretical capacities 11 Area = 2.63 sq.ft. Area = 20.11 sq.ft. : : : Minor Storm : : Major Storm Slope : Red. Minor Q V Major Q V (X) :Factor : X : (cfs) : (fps) : X : (cfs) : (fps) . 1 0.40 : 0.50 : 86.71 : 2.74 : 2.09 : 696.73 : 22.03 : 2.19 : 0.50 0.65 86.71 : 3.99 2.33 696.73 32.02 2.45 0.60 : 0.80 : 86.71 : 5.37 : 2.55 : 696.73 43.17 : 2.68 : I0.70 0.80 : 86.71 : 5.80 2.76 a 696.73 : 46.63 2.90 : 0.80 : 0.80 : 86.71 : 6.20 : 2.95 : 696.73 : 49.85 : 3.10 : 0.90 : 0.80 : 86.71 : ' 6.58 : 3.13 : 696.73 52.88 : 3.29 : 1.00 : 0.80 : 86.71 : 6.94 : 3.30 : 696.73 : 55.74 : 3.46 : I1.25 0.80 : 86.71 : 7.76 : 3.69 : 696.73 62.32 3.87 : 1.50 : 0.80 : 86.71 : 8.50 : 4.04 : 696.73 : 68.27 : 4.24 1.75 : 0.80 86.71 : 9.18 : 4.36 : 696.73 : 73.73 : 4.58 : I2.00 : 0.80 : 86.71 : 9.81 : 4.66 : 696.73 : 78.83 : 4.90 : 2.2S : 0.78 : 86.71 : 10.15 : 4.95 : 696.73 : 81.52 5.20 : 2.50 0.76 : 86.71 : 10.42 : 5.21 : 696.73 : 83.72 : 5.48 I 2.75 : 0.74 : 86.71 : 10.64 : 5.47 : 696.73 : 85.50 : 5.75 : 3.00 : 0.72 : 86.71 : 10.81 : 5.71 : 696.73 : 86.89 : 6.00 : 3.25 : 0.69 : 86.71 10.79 : 5.94 : 696.73 : 86.67 : 6.25 : 3.50 : 0.66 : 86.71 : 10.71 : 6.17 a 696.73 : 86.03 : 6.48 : I3.75 : 0.63 : 86.71 : 10.58 : 6.38 : 696.73 : 85.00 : 6.71 : 4.00 0.60 : 86.71 : 10.41 : 6.59 : 696.73 83.61 : 6.93 : 4.25 : 0.58 : 86.71 10.37 : 6.80 : 696.73 : 83.31 : 7.14 : I4.50 0.54 : 86.71 : 9.93 : 6.99 : 696.73 79.81 : 7.35 4.75 : 0.52 : 86.71 : 9.83 : 7.19 : 696.73 78.96 : 7.55 : 5.00 : 0.49 : 86.71 : 9.50 : 7.37 : 696.73 : 76.34 7.75 : 5.25 0.46 : 86.71 : 9.14 7.55 : 696.73 : 73.43 7.94 : I5.50 0.44 86.71 8.95 : 7.73 : 696.73 : 71.89 8.13 5.75 0.42 : 86.71 : 8.73 : 7.91 : 696.73 : 70.17 : 8.31 : 6.00 : 0.40 : 86.71 : 8.50 : 8.08 : 696.73 : 68.27 : 8.49 : 1 I I I I 1 e,/ I0 0 i al z' CLIENT ci,-.1 c:::, . ...„,,47.7,--ci-A,_,Qs. 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PG M OrlrlririNNNNNNNNNNNNNNNNNNNNN W tCO W W W W WWW W W W W W W W W W W W W W W W W W a In MIn01NMd' u110NNn W W to01M01010101000000 ,a N 0100rirtr4rir4r1e-i .-irlrlr4rlrirlrir11-4NNNNNIV s c0 c W W W W W W W W W W W W W W W W W W W W W W W Z 0 d' InOMu110 W CC101000e-Irir-� r-INNNNMMMMMM I g . . . . . . . . . . . . . . . . . . . . . . . . . . N ' W010000000r1r1r1rir1r1r1rlr e-1 l "-11.1rir t'iHri N N W W W W W W W W W W W W W W 00 W W W W W W 00 W W In W N W rl d' In N n W d1 01 O O ri ri rl rl rl N N N M M M M M rt 10 W W 0101010101010101000000000000000 bN N rr N N N NNN co co co W co co co W CO CO W W 00 00 co 0 Wrei0d' 1- 01OTAN11Md' d' (nmMul1010wW1-. NOWw O . 00 . 00008 . 004 . 00M00000000 111 r-I d' 1D N N N N to W W W W CO CD W W W CO W W W W W W W W W N N N N N N 1- N N r N N N l- n N N N N N N N N N N N 0 M O tr O S W W S N N W 1D 10 1n M M N N M W d' r4 01 W / . O ONNNNNNNNNNNNNNNNNNNrlHHH00 NNNNNNNNNrnrNNNNNNNNNN NNNN x E4 — 00000000000000000000000000 O U' E4 o o 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0. 0 0 0 0 0 -14Z44 rINMsYI koN W 010r1NMd' u110nto010ln0I0i0 c 4 N s— ri ri ri ri rl ri t-1 ri r- rl N fV M M d' d' In a MARCH 1991 8-4 DESIGN CRITERIA I 0 I Zy zz 1 Table 8B C-Factors and P-Factors for Evaluating EFF Values. Treatment C-Factor P-Factor I BARE SOIL Packed and smooth 1.00 1.00 Freshly disked 1.00 0.90 I Rough irregular surface 1.00 0.90 SEDIMENT BASIN/TRAP 1.00 0.50'" II STRAW BALE BARRIER, GRAVEL FILTER, SAND BAG 1.00 0.80 SILT FENCE BARRIER 1.00 0.50 IASPHALT/CONCRETE PAVEMENT 0.01 1.00 ESTABLISHED DRY LAND (NATIVE) GRASS See Fig. 8-A 1.00 1 SOD GRASS 0.01 1.00 TEMPORARY VEGETATION/COVER CROPS 0.45'2' 1.00 IHYDRAULIC MULCH @ 2 TONS/ACRE .............................. 0.10' ' 1.00 SOIL SEALANT 0.01-0.60'4j 1.00 1 EROSION CONTROL MATS/BLANKETS 0.10 1.00 GRAVEL MULCH I Mulch shall consist of gravel having a diameter of approximately 1/4" to 1 1/2" and applied at a rate of at least 135 tons/acre. 0.05 1.00 HAY OR STRAW DRY MULCH I After olantina arass seed, apply mulch at a rate of 2 tons/acre (minimum) and adequately anchor, tack or crimp material into the soil. Slope (%) 1 to 05 0.06 1.00 6 to 10 0.06 1.00 11 to 15 0.07 1.00 16 to 20 0.11 1.00 I 21 to 25 0.14 1.00 25 to 33 0.17 1.00 >33 0.20 1.00 1 NOTE: Use of other C-Factor or P-Factor values reported in this table must be substantiated by documentation. (1) Must be constructed as the first step in overlot grading. / (2) Assumes planting by dates identified in Table 11-4,thus dry or hydraulic mulches are not required. (3) Hydraulic mulches shall be used only between March 15 and May 15 unless irrigated. (4) Value used must be substantiated by documentation. 1 I . I MARCH 1991 8.6 DESIGN CRITERIA I 411 II -az/ za ITable 8-B C=Factors and P-Factors for Evaluating EFF Values (continued from previous page). Treatment C-Factor P-Factor I CONTOUR FURROWED SURFACE Must be maintained throughout the construction period, otherwise P-Factor = 1.00. Maximum length refers to the down slope length. I Basin Maximum Slope Length (%)_ (feet). I 1 --to 2 400 1.00 0.60 3 to 5 300 1.00 0:50 6 to 8 200 1.00 0.50 9 to 12 120 1.00 0.60 I 13 to 16 80... 1.00 0.70 17 to 20 60 .: .. :: . :. .: :.. .........: 1.00 0.80 >20 50 1.00 0.90 I TERRACING Must contain 10-year runoff volumes, without overflowing, as determined by applicable hydrologic methods, otherwise P-Factor = 1.00. I Basin Slope (%) 1 to 2 1.00 0.12 I 3 to 8 1.00 0.10 9 to 12 1.00 0.12 13 to 16 1.00 0.14 17 to 20 1.00 0.16 I >20 1.00 0.18 NOTE: Use of other C-Factor or P-Factor values reported in this table must be substantiated by documentation. I I I I I I I . MARCH 1991 8-7 DESIGN CRITERIA