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HomeMy WebLinkAboutDrainage Reports - 09/05/1989FAA*4 44009 tr aAO* &J 9/T/� T3D,NC Engineering Consultants 2900 South College Avenue Fort Collins, Colorado 80525 303/226.4955 Ms. Susan Hayes Stormwater Utility Dept. City of Fort Collins P.O. Box 580 Fort Collins, Colo. 80522 August 22, 1989 RE: OAKRIDGE VILLAGE P.U.D. EIGHTH FILING - CHANGES IN DRAINAGE REPORT Dear Susan: The purpose of this letter is to point out the changes recently made in the drainage report for the above referenced project. The two most significant changes are the elimination of Sawtooth Oak Court in the southwest corner of the development and the slight northern shift in the north property line of the development. These two changes slightly f6ffected the drainage basin areas within the site. The changes in basin areas are reflected in the revised drainage plan. Two year flow rates in- creased slightly at Design Points 4 and 5. These increases, however are easily handled by the prescribed drainage approach. Otherwise, the drainage patterns and flows remained the same as the earlier report. Calculations for the new sidewalk chase at the end of Redhud Crnrrt annaar in ralrr,lntinn F,.,t,;.,.; �V, narrative reDort. I trust this letter will clarify the changes made and expedite the approval process. Sincerely, G Nyt� Stan A. Myers cc: Bob Zakely, Everitt Companies 035-080 A\\����1tU11I i I1111111I�i/��� \NAQ REGjso �,r.,,,�, 18060 •� Y p: •c4 a Other Offices: Vail, Colorado 303/476-6340 • Colorado Springs, Colorado (719) 598.4107 ■rYINC Engineering Consultants 2900 South College Avenue August 22, 1989 Fort Collins, Colorado 80525 303/226-4955 Ms. Susan Hayes Stormwater Utility Dept. City of Fort Collins P.O. Box 580 Fort Collins, Colo. 80522 RE: OAKRIDGE VILLAGE P.U.D. EIGHTH FILING - DRAINAGE VARIANCE REQUEST Dear Susan: The purpose of this letter is to request a variance to the City of Fort Collins drainage design criteria as it relates to the curb and gutter capacity for the initial storm flows. The Oak - ridge Village P.U.D. Eighth Filing - Revised Drainaee Report dated August 4, 1989, by R.B.D. Inc. details the background and calculations for this development. The section of curb and gutter at issue is the south curb line of Redberry Court west of its intersection with McMurray Drive. Calculations show that the 2 year flows slightly exceed the capacity of the street gutter in the south curb line of Redberry Court west of its intersection with McMurray Drive. Several measures are being employed to address this potential problem. The curb type in this section is six inch vertical in order to provide additional capacity. In addition, no parking is allowed along this section of curb and gutter and access to Lot 24 will be off of Red Oak Court. The final foundation grades of housing on Lots 47 and 24 have been raised at least 2.4 feet above the adjacent flowline elevations to provide an extra factor of safety. It should also be pointed out that the landscape strip along the west side of McMurray Drive provides additional capacity as these flows turn southward. The final foundation grade elevations of housing in the Sixth Filing is well above the flowline elevation of McMurray (+5.0 feet). All these factors provide for safe conveyance of flows in this area. . Other Offices: Vail, Colorado 303/476-6340 • Colorado Springs, Colorado (719) 598-4107 Based on these mitigation measures we request a 'variance from .the normal drainage criteria for gutter capacity for the initial storm flows (Section 4.2 of the City of Fort Collins Storm Drainage Manual). Sincerely, Stan A. Myers P.E. cc: Bob Zakely, Everitt Companies 035-080 I ■�/YiNC Engineering Consultants 2900 South College Avenue Fort Collins, Colorado 80525 303/226-4955 Ms. Susan Ilayes Stormwater lltll.i.t:y I)ep(:. City of Fort Collins P.O. Box 580 Fort Collins, Colo. 80522 RE: OAK1(TDCE VILLAGE P.H.D. DRAINACE REPORT Dear Susan: ~48W v4r/w7 j0C1Ng1w Rev.,er August 4, 1989 EIGHTH FILING - UPDATED FINAL URI) Inc. 1.s pleased to submit t:his letter as the Final Drainage Report for the Oakridge Village P.U.D. Eighth Filing a planned unit development by Everitt Companies. L,OCAT.fON AND EXTSTINC CONDTTTONS This 23.29 acre site is located within the Oakridge Village development. The site is bounded on the south by the Sixth Filing of Oakradge Village. Tt: is bounded on the east by McMur- ray Avenue and on Like west- by Wheaton Drive. The area north of the site is undeveloped between this Filing and the existing Com- HA near Brrildi.ng. The principal drainage Swale in the area lies to the north of t:h:is leiling as well. More specifically the site Is located In the northeast rluart:er of Section 6, Township 6 Nor1.11, Range (i8 West, of I:ho fill' I'.M. The site is currently covered wal:h field stubble and grasses and slopes generally to the east_ and southeast: at a grade of one percent. The overal I drainage 11.1.an for Lhis area was covered in the Final Irainage Tlives 1:1Rat:ioil for Oakritigo Business Park dated May 17, 19117 by ,lames H. -Stewart and Associates, Inc. and The Final Drainage Report for the Seventh Filing of Oakridge Village P.11.D., Nevi.sed dated September 9, 1988, by RBD Inc. The earlier report called for a detenta.on area to be located in the northeast corner of "le proposed Eight:h Fi-ling. This pond was eliminated in the l.rtt:er report: by raising t:he maximum ponding elevation of the regionwide pond along t:he railroad embankment east of the Sevenl:h Filing (see Overall Drainage Plan attached). The prin- cipaI drainage swale :locat:ed to the north of this Filing carries detained fa.ows from the area nort:h of l:he Swale and undetained flows from the area south of the swa.le. Other Offices: Vail, Colorado 303/476-6340 • Colorado Springs, Colorado (719) 598-4107 DESIGN APPROACH The design approach t.jlcen for this site Is very straight forward. Off site flows are ant.ic:ipated for the time being from a small undeveloped area just north of the northwest corner of the site (see Basins 01 and 02 on Overall Drainage Plan). The 100 year flows from this area are mini.ma.l. When the area to the north is developed these flows w I I I be channeled northeast and will no longer enter I:he site. No on site detention is required based on t:he overall. drainage plan for the Oalcridge Village area which is outlined in the latter report referenced above. The site is divided Into three subbasins draining into the street system and adjacent dralnago swale. Through these conveyances the un- d(0:ained 17'1Ows eventual.ty reach the regionwide detention area, where the flows are detained. One of the cr:itica.laspects of the final design is to determine if the proposed street system has the required capacity for the i.nit:ial. (2 year) storm. The attached calculations show that the 2 year flows slightly exceed the capacity of the street gutter in the south curb line of Redberry Court west of its intersection with McMurray Drive (design points 4 and 5). Several measures are employed to address this potential problem. The curb type in this section is six inch vertical in order to provide additional capacity. In addition, no parking is allowed along this section of curb and gutter and access to Lot 24 Is off of Red Oak Court. The final. foundation grades of housing on lots 47 and 24 have been raised at ].east: 2.4 feet above the adjacent flow.line eleva- tlons I:o pcov:icle an exl:ra factor of safety. .it should also be pointed out that the landscape strip along the west side of McMurray Drive provides additional capacity as these flows turn southward. The final. foundation grade elevations of housing in the Sixth Filing is well. above I:he flow.Line e.levat:ion of McMurray (+5.0 feet). All these factors provide for safe conveyance of flows in this area. Another aspect: of: final clesi.gn concerns the principal drainage swale along the north side of t:h s filing. This swale is designed to carry flows from the areas adjacent to it between Wheaton Drive and McMurray Drive. In addition, it carries upstream flows from the areas north and west of Wheaton Drive. In Lho aroa between Wheaton Drive and McMurray Drive areas south of "It! swale flow .Into at undetafned. Areas north of the swale are detained and released into the swale at a rate of 0.5 c.f.s. per acre. The offsite, uncletalned, and detained flows total 152 c.f.s. at a design point (design point 2) just north of the swale's crossing with McMurray Drive. It should he pointed out that this figure (152 e.f.s.) is conservative because the method used does not Lake into account the timing of peak flows. This quantity of flow requires an additional culvert at the swale's crossing with McMurray Drive. The attached calculations determine the size of this new culvert Drainage wil.l. flow 1:hrough this site in a controlled manner when the finaldesign is implemented. This approach will satisfy the hydrologic and ►rydrau:i.ic concerns and current City of Fort Col- Lins standards for storm water management. Slncere.ly. Stan A. Myers P.R. cc: Bob Zalcel.y, Everitt Companies 035-080 GUTTER CAPACITY CALCULATIONS Q w cc G J W cr U) w z cc 0 WIN IIIIIIIIIIIIIIIIIII NER HIM MEIIIIIIIIIIIIIIIII n, IMMUNEUILU HIM 11111111111111111111111111 e , ,9 �I IN Lh cn - DRAINAGE CRITE^' ',ANUAL RUNOFF 50 30 ►- 20 !z w U IY w a 10 z w a O 5 fN w cc 3 O U 2 w F- 3 1 NIP. ii r ■■i■ ■loll■■ ■■■■■�■ �I��I%�■ ■ �I��I =D..►I I�■ �' %■ ■■■■� ••■••►� t MEMO �iri■�i�C■ �i AR FAR ■■NNEN 5` 5 •3 1 d 1. 2 3 5 10 20 VELOCITY IN 'FEET PER SECOND FIGURE 3-2. ESTIMATE OF AVERAGE FLOW VELOCITY FOR USE 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 ---- —' — URBAN DRAINAGE & FLOOD CONTROL DISTRICT DRCOG TDINC Engineering Consultants CLIENT PROJECT MADE BY - DATE JOB NO CALCULATIONS FOR - CH ECKED BY - DATE SHEET - OF 60 P.- 2/00.3 2.7.4 : r-, ' A,=' gia's + 7.3! 4 11,3 �2 H GUTTER CAPACITY CALCULATION 6 INCH VERTICAL CURB 2 YEAR STOF-31- I'1 p :19 Q= A (I - 486/1-0 (r". 666) 5) (REDUCT. FAc,rOR) A= r-0. 10571-19 F", = (I . i") I ', Q ... ...... . RED. F. S5 RED. F. 6. 07 65 2. 5 15.67 i t. 75 0.6 3. 1? 0. 80 3.0 16.48 0. 72 0.7 8.84 3.5 16.07 0.65 C3 9.45 4.0 15.05 60 (.-.).9 1. f.). C) 3 CA(.) 4.5 15.41 0.55 1.0 10 . 57 it.80 5, . 0 14.77 0. 1. 1 :11 . 00 i i. 80 5.5 17-11.94 0. 45 1.2 11.58 G C.) 6.0 12.94. 0.40 1.2. 05 it. [jo e.). 5 1'2:. 46 ().,--.'7 1.4 0. BE) 7.0 11.53 0 . 3-11, 1.5 12.94 C . 0C ..) 7.5 1 (). 85 C).:--,(:) 1.6 13.37 0.80 8.0 10.46 0.28 1.7 13.78 0.80 0.5 10. 01 0. 26 1.8 111.18 0.90 9. 0 9.51 0.24 1.9 14.57 0.00 9.5 0.96 0.22 2.0 1 11. . 95 0.80 10.0 8.36 0. 20 CLIENT eu&perr JOBNO.03.5- • _ ■��INC PROJECT CiAICi2. 1/I,C�AiaL= �� CALCULATIONS FOR rl95 C?kP a) 1::w-5(8t) PTA Engineering Consultants MADE BY 5AT DATE-` _CHECKED BY DATE SHEET OF %DINC Engineering Consultants LIMITS OF GaG. OD ro A jam- FLOW LINE ZwNi 0.14) DRIVE -OVER CURB, GUTTER AND SIDEWALK I. ArrA 'A 4.7S4 t, 17 j; z' 0.40 A reA 8 CLIENT PROJECT JOB NO. CALCULATIONS FOR MADE BY - DATE - CHECKED BY - DATE SHEET -17 .. 31911 (1.421 sTL A?C*P- Z8)(-/4, 97 )12 40 TbrAl, FdrA' j P" 14 4/7 14.2 le. e. rx 0./Seb rv3, I � DRIVEOVER CURB a f 6)1.293S 2 YEAR STORM: b,jp= 16.69 A(I.486/ri) (I,".666) 5) (REDUCT. (=ACTOR) A= 2.65 r=0.156777 rw= Q. 0 1:31 RED. F. 0. 5 0.64.08 5.51 0. 7 5. 95' 0. a 6.36 0.9 6. 74 1, 2 7.79 1 . 7. 1.4 8. .111 1.5 3.71 1.6 1.7 1.2 1.9 RED, 0. 90 615 1. 6 6 0.60 4. 151 10. -37 0.55 r: 5. 0 9. 9:_'� 0. �(- 'j.) 5. Sj 9. 30 0. 45 6.0 R. 71 0.40 6.5 8.310 0. 37 7.0 7.76 0. 3' 7.5 7.30 0.30 8.0 7.04 0.23. 8.5 6.74 0.26 .9. 0 6.4o 0. 24 C? a- * - . ­: 6. ()2 0. 22 10. () . r.-). 62 1.). 2(-) OF 0.1 0, Bel 0.9 ■rfYiNC Engineering Consultants CLIENT E "ITT c� JOBNO.(::)_:3f;-�F� PROJECT OA K R 1 D6E 1111L, 8� � CALCULATIONS FOR _M4_67 CAP 0 Q <—l4.1/ pr,2 MADE BV 5AlI^ DATE Z%4 CHECKED BV DATE SHEET OF I CAL f A av Tic) �R cAP le Jr (D �?l / fti io' -TYPE' K IAII i I ff 014:"' 4 17;= 0133 Q,�QI- � 651 F(Co„S SI I I {FRou i I '3 4 PlanAi 9.4(0�3�'!/.,Iris.. ,F14..5-5' Fr Ftaral FlG S-6 �A�vt E T=f5) 7, 3 iv'ro iuc�-r i c=ram E 6 I r c�Q , I 1 I I r I ! _ I I I. : I I i I I • V - t _ r I I No Text No Text Base width = 2 Side slope = 5:1 Slope = .02 Mannings n = .035 Hyd.D. = Area/Top Width Froude No. = Vel. / sq.rt(g * Hyd.D) Depth Discharge Velocity Area Hyd.Rad. Hyd.D. Froude No. (ft) ----- (cfs) --------- (ft/sec) -------- (sq.ft) (ft) (ft) 0.20 1.0 1.7 ---- 0.6 -------- 0.149 ------ 0.15 ---------- 0.8 0.40 3 9 2.5 _ �tfj� Q. 7. 3 .0. 2 7 0 8i�ii riA� , roar l 0.60 9.3 3.1 _._. 3 • 0...,_.___ __�.,_4____ _.__4�.3�__ __._ Q . 9 ..ioove 0.80 17.5 3.6 4.8 0.473 0.48 w 0.9 1.00 29.0 4.1 7.0 0.574 0.58 .1.0 1.20 44.3 4.6- 9.6 0.674 0.69 1.0 1.40 63.8 5.1 12.6 0.774 0.79 1.0 1.60 87.8 5.5 16.0 0.874 0.89 1.0 0 ■rYiNC Engineering Consultants CLIENT EUE-P/T7' JOBNO. 035 -080 PROJECT if)AVP I Drr%e5 VIL CALCULATIONS FOR MADE BY- DATE CHECKED BY DATE SHEET_ OF • S \i,Ew'R��c cHp;�Sh �� , 5��,�. 10/�.t� L c?wi�T { I i,>"vEx�/ic5vs .9ed--A' ,GANG PA�t� A764C 0:26, D. %gS - -I 4,00 �r�1:9) 1 FK 52o2t-t �.Awac�F C��Tk-�\A. C'tc.��J/•�� Z-8� cf5 C'A6 `4+ = 3.51 F� t2o n { / t q 2� �-r v St 4 {r•- SIOtwA\k ci+ASS j USi,vG, fJ-/3 'sl�Ga�,4;LlC CvzUEIeT _, ;._.._ '.. OP=bS /4f3� • I , p 0/3 I , I � I cQ- ©3g Q �4a16�,o1 it-'/3 �,44�/ 0/3 = CJ.�i3r ` r Fo,e .C7Ye. 1 6j1C>k-_vQA � \p�jE Ir�1 2�c�8`l 'o`1CLi j 1 7 Z AAr C L S � 2 I S D .mil bb E}_!._per@.O.6 C �60�6� LHAt:� i SWALE CAPACITY CALCULATIONS %DINC Engineering Consultants CLIENT ,cVjfr 7--r JOBNO. c_) 'O8O PROJECT-CM-9 VIA` 8pt& CALCULATIONS FOR —MPAMIA4E MADESYSALIA DATEZ_L% CHECKED BY DATE SHEET OF /(,''iy.F,AC: Iat, 9> J'Aail& �G.14( ©AYP.i SLL%. r4•�'l: /G>� .k't'S�C. �T . .OotwS 4r< jf ' 'emm A,PEAA Sny ii/ OF c)Cr:�, I ; ,4,46 ; I i !!Ark''.8 AR6-A wo'rr4 ©Fl �Ccui/C,ivE74e:C VALUE 7�1k!<a/\G2 At5 VASE ., ,[vOt5r' J AeEJ4 0r OAKt' 8J{A/isinJ c�'. . 7 / ` Q �o;�r�C►sX4:la�,7i ICo7 83cfs FPr Ax�� 4�7l o'F EGA+A/C' Sc�ca�ta P�..FvTc�e�C�AK.F'. .3.g8A(t (�`d4.�c�s��tc I rscr, o7 0s 0 IN. IAMB t-i'rEA�, __...... A. c C'A wr--L"R'V. A r,'t- A = 2. 2 5 -76 2,45 DRAINAGE CRITERIA MANUAL INLETS 9 CULVERTS N z 2 W I i i JIN r u H r iv O •,1 u J AA13011A W A71Afl0 WU N n = VI �' r ~ ■ M Z nl U 11111011AM07 UI W Q fn N �1I j W ' O N N It r J Q = = e W W u Z J x I t N1 Z 1 J y111 = J W O = to o 49 H x 0 N 1� ra 'n , a 2 ; x O u J cr a a c� Z to II W H + O 2 2 ` ; OZ u _O O ^O Q j" a W o a O Ix W = J D x W J J n O • ' v1 U1 �� = W W o J z = In �� Z H (H fn N fn Z Q Q W $ O ca 2 O W 349 ; a u W Fillic 9 Y = O (y,, = u u u U) W x o 11 N ill r t,1 L) H O ` O u 1q 4 f- 11 Q W 0 = J 13 � 11 11 0 �N o iQ Z U) E 1 uw = 1 � V h Sufi From RPR N FIGURE 4-4. DESIGN COMPUTATION FORM FOR CULVERTS t1-15-68 Denver flogionel C/ , of Governments U) z Z W f n O 3 � ~ JIO U H 0 O U J AAIOO13A W 1311no or _ .. u .N W Z U O0 I"' U W LLJ 0 NI110 tl1N0� 0 Nota I I W Q (n U) W W p 3 > n J Q = Q o U 2 W 2 H I to 3 t� V J W W Q 0 J i 2 1 J 2 J O o W L ' + _ ►n 4� rt a ; f x F3 V7 1�1 U N t� I I 0 W 1- y N Z II 11 F- Z v O Z Z 3 U O O ff v Q Q O = J Ca cr W o x W 2 W W o� h o In Y Q O O w W w a> Z U) Z ; Q Q W U Z ao 3 3 2: or � o U Q Q = Z o I ` V) U Q Ln Q o W H W Z 1 U U O N U OJ O U W W O N it 0 O O I- >- W a W J U a Q D N H U W z Q W rom 8PR N Figure 6-1 DESIGN COMPUTATION FORM FOR CULVERTS MAY 1984 6 2 DESIGN CRITERIA DRAINAGE CRITERIA MANUAL INLETS 8 CULVERTS ISO 10,000 From BPR 16e 0,000 EXAMPLE (1) (2) (3) I56 6,000 0•42 Icahn (7.6 fool) 6. 144 b000 D.I20 $to , b. 4.000 • Hot 6. 132 toot 3,000 4. 120 106 2.000 It► t.! T.T 4. 3. all Is feel 96 1,000 3' 900 e4 600 / S00 72 400 / to Y. Z 300 2 M / q = 60 u too W ^, 2 / W c b4 / Q /W 100 W > 4e / a e0 = a F 4p 60 d 0 c SO Hw ENTRANCE O Ir 40 SCALE D TYPE W 10 W F W 3e 3a (1) S4een Nod with 44 33 e•u..0 ; c 9 a c a 20 (t) aeoo• .0 with W 30 Modwe11 = (3) Groove sad •6 Y7 rnluUy t0 Y4 6 .7 6 To use scale Itl or 131 poles► YI 5 eerltoetelly to codes (1).t•ee 4 list weight I•eluu Ile* teroy D lie• D eeelee, or reverse as 3 Illestreled. 6 le 2 Ib 11.0 .b 2 1.5 k 1.5 L It For design, use charts and nomographs in chapter 10. FIGURE 4-2 INLET CONTROL NOMOGRAPH EXAMPLE IL-15-68 Denver Regional Couf .t Governments DRAINAGE CRITERIA MANUAL INLETS & CULVERTS t000 M T H ke r 4 1000 D J MAiA[[D OUTLET [ar[aT gArMa FULL Her - N. he-L$o e00 1!0 hr w1M1 slew .w maw, aayMF ■• b. 6 r d�ibo in w 600100 pwaiw soo 106 From BPR • S00 ♦ts 1.0 400 e4 300 7t ' es too e0 ! r •4 / = It / Itso 4e O.N !w -''` JIB 3 �_ o k so 40 30 t0 to s s s � !3 W la 30 a at � t7 !4 tl la Is I! IPW t W 4 I �p W- S _w0 4 too dd0 S 0 �• •. O 10 .qb 1 o For design, use charts aM narrogra^ n chapter tQ FIGURE 4 -3 OUTLET CONTROL NOMOGRAPH EXAMPLE to II-15-68 Denver Regional Co Of Governments Base width = 5 Side slope = 4:1 Slope = .0083 Mannings n = .035 Hyd.D. = Area/Top Width Froude No. = Vel. / sq.rt(g * Hyd.D) Depth Discharge Velocity Area Hyd.Rad. Hyd.D. Froude No. (ft) ----- (cfs) --------- (ft/sec) -------- (sq.ft) (ft) (ft) 0.10 0.4 0.8 ---- 0.5 -------- 0.093 ------ 0.09 ---------- 0.5 0.20 1.4 1.2 1.2 0.174 0.18 0.5 0.30 2.8 1.5 1.9 0.249 0.25 0.5 0.40 4.8 1.8 2.6 0.318 0.32 0.6 0.50 7.1 2.0 3.5 0.384 0.39 0.6 0.60 10.0 2.3 4.4 0.446 0.45 0.6 0.70 13.4 2.5 5.5 0.507 0.52 0.6 0.80 17.4 2.6 6.6 0.566 0.58 0.6 0.90 21.8 2.8 7.7 0.623 0.63 0.6 1.00 26.9 3.0 9.0 0.679 0.69 0.6 1.10 32.6 3.1 10.3 0.735 0.75 0.6 1.20 38.9 3.3 11.8 0.790 0.81 0.6 1.30 45.8 3.5 13.3 0.844 0.86 0.7 1.40 53.4 3.6 14.8 0.897 0.92 0.7 1.50 61.7 3.7 16.5 0.950 0.97 0.7 1.60 70.7 3.9 18.2 1,003 1.02 n 7 1.70 80.4 4.0 20.1 1.055 1.08 0.7 1.80 90.9 4.1 22.0 1.107 1.13 0.7 1.90 102.1 4.3 23.9 1.158 1.19 0.7 2.00 114.2 4.4 26.0 1.210 1.24 0.7 2.10 127.0 4.5 28.1 1.261 1.29 0.7 2.20 140.7 4.6 30.4 1.312 1.34 0.7 2.30 155.3 4.8 32.7 1.363 1.40 0.7 2.40 170.7 4.9 35.0 1,413 i 4S n 7 2.50 187.0 5.0 37.5 1.464 1.50 0.7 2.60 204.2 5.1 40.0 1.514 1.55 0.7 2.70 222.4 5.2 42.7 1.565 1.60 0.7 2.80 241.5 5.3 45.4 1.615 1.66 0.7 2.90 261.6 5.4 48.1 1.665 1.71 0.7 3.00 282.6 5.5 51.0 1.715 1.76 0.7 Base width = 5 Side slope = 4:1 Slope = .0083 Mannings n = .035 Depth Discharge Velocity Area (ft) (cfs) (ft/sec) (sq.ft) Hyd.D. = Area/Top Width Froude No. = Vel. / sq.rt(g * Hyd.D) Hyd.Rad. Hyd.D. Froude No. (ft) (ft) ----- 0.10 --------- 0.4 -------- 0.8 ---- 0.5 -------- 0.093 ------ 0.09 ---------- 0.5 0.20 1.4 1.2 1.2 0.174 0.18 0.5 0.30 2.8 1.5 1.9 0.249 0.25 0.5 0.40 4.8 1.8 2.6 0.318 0.32 0.6 0.50 7.1 2.0 3.5 0.384 0.39 0.6 0.60 10.0 2.3 4.4 0.446 0.45 0.6 0.70 13.4 2.5 5.5 0.507 0.52 0.6 0.80 17.4 2.6 6.6 0.566 0.58 0.6 0.90 21.8 2.8 7.7 0.623 0.63 0.6 1.00 26.9 3.0 9.0 0.679 0.69 0.6 1.10 32.6 3.1 10.3 0.735 0.75 0.6 1.20 38.9 3.3 11.8 0.790 0.81 0.6 1.30 45.8 3.5 13.3 0.844 0.86 0.7 1.40 53.4 3.6 14.8 0.897 0.92 0.7 1.50 61.7 3.7 16.5 0.950 0.97 0.7 1.60 70.7 3.9 18.2 1,003 1.02 0.7 1.70 80.4 4.0 20.1 1.055 1.08 0.7 1.80 90.9 4.1 22.0 1.107 1.13 0.7 1.90 102.1 4.3 23.9 1.158 1.19 0.7 2.00 114.2 4.4 26.0 1.210 1.24 0.7 2.10 127.0 4.5 28.1 1.261 1.29 0.7 2.20 140.7 4.6 30.4 1.312 1.34 0.7 2.30 155.3 4.8 32.7 1.363 1.40 0.7 2.40 170.7 4.9 35.0 1.413 1.45 0.7 2.50 187.0 5.0 37.5 1.464 1.50 0.7 2.60 204.2 5.1 40.0 1.514 1.55 0.7 2.70 222.4 5.2 42.7 1.565 1.60 0.7 2.80 241.5 5.3 45.4 1.615 1.66 0.7 2.90 261.6 5.4 48.1 1.665 1.71 0.7 3.00 282.E 5.5 51.0 1.715 1.76 0.7 tY t T3D,NG Engineering Consultants 2900 South College Avenue Fort Collins, Colorado 80525 303/226-4955 January 24, 1990 Susan Hayes Stormwater Utility Department City of Fort Collins P.O. Box 580 Fort Collins, CO. 80522 RE: OAKRIDGE 8TH REPLAT - ADDENDUM TO 8TH FILING DRAINAGE REPORT Dear Susan: The purpose of this letter is to clarify the fact that the replat of nakridge village 8th Filing had no effect on the drainage plan and insignificant effect on the grading plan for the 8th Filing. The replat affected only the lots surrounding Last Oak 'Court (formerly Silk Oak Court). The number of lots actually decreased. Drainage patterns remained the same and the only grad- ing changes made were related to the new lot line locations and finish floor elevations. All pertinent sheets on the utility plans have been revised to reflect these changes. No changes were made that would relate to the previous drainage calculations. I trust the letter addresses your concerns. Please call me if you have questions. Sincerely,31`s 5060 Stan A. Myers P.E. ,r000 E L0 nw cc: Bob Zakely, Everitt Companies 035-105 Other Offices: Vail, Colorado 3031476-6340 • Colorado Springs, Colorado (719) 598-4107