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HomeMy WebLinkAboutBLEVINS SUBDIVISION LOT 9 PUD FINAL - 42 91B - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTFINAL DRAINAGE & EROSION CONTROL REPORT FOR LOT 9, BLEVINS COURT, P.U.D. FORT COLLINS, COLORADO MARCH 2, 1992 PREPARED FOR: KENT GLOVER PREPARED BY: PARSONS & ASSOCIATES CONSULTING ENGINEERS 432 LINK LANE PLAZA FORT COLLINS, COLORADO 80524 (303) 221-2400 PROJECT NUMBER: 91.15 GLV R PARSONS &CLIEN 41 `�w — JOB NO. / 1 cl V ASSOCIATES PROJECT Lef 1, '^r�L?V )n f &,Lf CALCULATIONS FOR ho If( MADE BY DATE 5/ CONSULTING ENGINEERS WC 115- 2 CHECKEDBVDATF SHEET 2 OF ,J Ft. CoBitr. Colordo 8WM pivffoj-e fk9off 140� G1-osS of lX If 70PU c =. 9 Tce _ / fz ((L-12- 0,o)(1)) lop l�117 (10)(_7T 1))70 Tc,00 1.57A1.1- 1•ts(z)) lvo 11�f�Cc,1)-(r•ts)l9) o= 1s70 f. 1.97 = 17.7IN' l� Fam rywt, 3-1 rz = 1, F roo = s•s Q2 - (I•o)23 cfs Q r" = (1,u) (f;I) (s 5) (.zT) = 87 cfs C I( C �7 PARSONS & Ir1— ASSOCIATES CONSULTING ENGINEERS Ft, C'uhm, Colorado 8=4 CLIEN P41 clove( ,/ — JOB NO. 116 " 1 " PROJECT ILa� Rl I O Fdla3 Nl //r. Ad CALCULATIONS FOR 9{ � I/0^ MADE BV " N ` DATE l -1 Y-V CHECKED BV DATE SHEET OF Of4m)l(10 Ka'ume g1u0 = L zs G Y7) z ( 0 ? ) = - 4 S Tc -E Qw V 00or V J) �rvlctfw ("/1) ((fs) m3) ((fs) (f1 io 7.25 1.14 11 CC 430 Zo Sli 0.82 7F 1 l3Z F2 av y 1s 0. 4 /188 198 770 yv 3,s-0 0. si )3Yl 26Y 1080 5u 300 0.`l8 J990 ' 330 1110 da 2'a ,V 1512 M 1)16 � Y 2-?0 0.37 I M 46 Z 10 9 Z k ?,6 0,33 ISSN 528 1056 _de_l ej f,io4 wi�� dr IIl6 cv1r� fuf. C C PARSO�NSTC& CLIEA ri' ! I #vff �{� _ JOB NO. 91 /S 6 LV MASSOCIA 1 arS PROJECT —Z i pl e(114CS 6'(I rt 41V CALCULATIONS FOR OT ,1111�n CONSULTING ENGINEERS MADE BY WC DATE t ' CHECKED BY —DATE SHEET OF Ft. CoMm, Colorado SOS24 fiblilem . Ql eJf7 n V0,10m e EQJt CY4 4ve Wesf CK(d LrM .51 leq DI Wq . s3 ,z.c1 �? (7s 1. s)) (5)) = 33, 9ZS f{- )3 W , Jr 12.71 J}raq : lz (sc 1,3Y) (D) i41� PAI�J- 1ef 3 VolurK.c fit All SfW = 29 oZ sb H X 3) 'vlVr = 1073. j 0 FI. rs' � r3.�y n.ry IE' w,rk .n 1LSY V�IuM ` AIL �56ty) (IS) _ yZ x�i•0'ldil�f = %S6 T la/ Va/uw la Ca/crnlu/e/ %y Goss Secfl�r = IfY9.� CFi �r7 J > ia6 (eyullel Tn q M fAY &f4l sf" jal{r will bast �,p in e t� aaf� sw_vles ale. - l 1k I ad soq 14 Sd es e f pad ola% 4'0� 1��. 74�s fa rp�ovrr4 adci, via deP4fran. T�Ije limifs aye wo of � d/014'sp plats. C a PARSONS & Irk ASSOCIATES CONSULTING ENGINEERS Ft. Collim, Colorado 80524 CLIEA /n7L KA I.y ZV/�!/ e'//J — JOB NO. ?o ct V PROJECT -lot b le&4;� js Q�`-eut fI m CALCULATIONS FOR ' /G t MADE BY `� We DATE I CHECKED BV DATE SHEET Of �_� z' 6yy Ff/t _ - L � 004 f pie, y � i 3 13 // - i (g) : i i 7 RAINFALL PERFORMANCE STANDARD EVALUATION .1--------------------------------f------------------------------------� PROJECT: LOT Blfvm"s Cee� P•u D STANDARD FORM A (COMPLETED BY: Jeff COUCH DATE: 3`Z-72 I � DEVELOPEDIERODIBILITYI Asb I Lsb I Ssb I Lb I Sb I PS I ISUBBASIN I ZONE I (ac) I (ft) I (%) .((feet) I (%0) 1 (0b) I - --------I-----------I------- I ------- I ------- I ------- I ------- I-----FI j Loi l niluaie 0.17 1 60 1 2.0 1 1 1 77-0 1 I I I I I I I I I--------=------------------------------------------------------------ HDI/SF-A:I929 EFFECTIVENESS CALCULATIONS -------------------------------- -------------------------------------- PROJECT: Lot q� 81ew5 Cculf) P.O.P. STANDARD FORM B I COMPLETED BY: Jeff: Couch DATE: 34 1? Erosion Control C-Factor P-Factor Method Value Value Comment ------------------------------=--------------------------- B4rC Serl i•D I.0 Paikr:� �-ot ftlail riked C45S 0.OP 1 o U,dkftw64 back of Lot Sceirm re f Trap Gravll Fifer 1.0 1.0 O. So 0•10 _Tn Pwk� A<<, -TnQw4l Le f /}raOn1(r --------Baita�r Arco---------011 --------------------------------------- I.00 MAJORI BASINI PS (9) SUB SAS1IN AREA (Ac) I CALCULATIONS Lof 11 77.0 1 O. 11 ! FsW ils-W Grass ------------- (0.08 /}(.,?s) Qac 6►rorpd (.19 dries) au�rdr�s Rica (0.05- furs) Wf�yhk� nCi, Fador i I K . ►y) t (0.1 x .01) t (0.OI X . DY) _ S` .z7 - We(144 , P 4 Fodor 0.s x 0•Y = 0.40 -I. ®P F,.({,, EFf = El - (0.9 x 0,y0)] x Ioo = 79 Z I I i i I I I I I I ---------------------------------------------------------------------- HDI/SF-B:1989 �• _ CONSTRUCTION SEQUENCE _ I PROJECT:% Lei p'{v�S coul, US ' STANDARD FORM C SEQUENCE. FOR 19 9Z ONLY COMPLETED BY: Jeffcouck DATE: . Indicate by use o•f 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. YEAR .T—I-T-1 MONTH ____ i .� I� i t1 I Pf I /� I -- S I O I N ICJ ------------- OVERLOT GRADING I - ',JIND EROSION CONTROL I I Soil Roughing I I Perimeter Barrier I I Additional Barriers I. I Veoetative Methods I I Soil Sealant I Other I I Grac�r+. RAINF'.LL EROSION CONTROL rIr Bvl/("� frad� ky STRUCTURAL: I Sedlment•Trap/Ba"in j I Inlet Filters l: .Straw Barriers Silt Fence Barriers l l Sand Bags I I Bare Soil Preparation I Contour Furrows I I Terracing I` I Asphalt/Concrete Pavi ng I ' Pa/kliqj Lot I Other I _ I Cu. S��qC Me l I S I .VEGETATIVE: Permanent Seed Plantinal Laf J(6/11 I ;Mulching%Sealant I I Temporary Seed Plantinal I. Sod.Installation I I Nettings/Mats/Blankets I . I Other I l I ---------------------------------------------------------------------------------------- STRUCTURES: INSTALLED BY MAINTAINED BY VEGETATION/MULCHING CONTRACTOR DATE SUBMITTED HOI/SF-C:1989 APPROVED BY CITY OF FORT COLLINS ON u FINAL DRAINAGE & EROSION CONTROL REPORT FOR LOT 9, BLEVINS COURT, P.U.D. INTRODUCTION This drainage investigation has been prepared along with final plans for the development of a duplex on Lot 9 of the Blevins Subdivision. This study was prepared in accordance with the City of Fort Collins "Storm Drainage Design Criteria and Construction Standards." SITE DESCRIPTION This project is to be constructed on Lot 9 of the Blevins Subdivision which is located at the southwest corner of Blevins Court in the Southeast Quarter of the Southwest Quarter of Section 14, Township 7 North, Range 69 West of the 6th Principal Meridian, Larimer County, Colorado (see figure 1)_ Lot 9 includes 11 ,846 square feet and was platted as part of the Blevins Subdivision in 1958. Lot 9 remains the only vacant lot in this area. Adjacent structures appear to be single family residences converted to rental usage due to their proximity to the Colorado State University Campus. These units are typically raised one foot above curb level with individual yards draining into street curbs. . t�• 3 w ore _ o Sg Y EM. � 3 V o • ; N N N i EMu w M.m.n sr M 1. S! Snn aQ 3 y N b 0 y WMyn.St 3 a fi elrcb S! 2 � • N � Q � ,fCF'YY,Oy M.lolw RtaA o D.�aeru%. a LSO E I! Z,J',it^ YC•.AB�1 Y{ O Unl�lf a.n Unl..nh Ar w.,rw.,ea N�a�T•`F''^S <!: •f.'yb ;. :V � rocE 'SVYM w: «T�K: t p•s!'"''4 tq l:.t »noaw 'a STA-1%, vm' Lm�[CI c ~ rB B...B Be •- IWLabS id -$ sl#Wns? SummMSl UNIVERSITY WY—. °d NMr.O. M... $ 7.m.up 4 or ¢ 26 cl. .C. HOW $! Jonlay Ln B. a F tM Sf cl 4 eltry �29] M SIw Sf WNbnb E VICINITY MAP PROJECT SITE FIGURE 1 This site slopes from west to east at about a 2.0% rate and is covered by natural grasses. It appears that no drainage facilities were constructed as part of the Blevins Subdivision and runoff is conveyed via streets in this area towards Spring Creek. All other utilities (including sewer and water) were located along back property lines and extend from South Whitcomb Road. CRITERIA The Rational Formula has been used to develop runoff flows from this site. The Rational Formula is an excellent predictor of flows from drainage basins with areas less than 200 acres. HISTORIC DRAINAGE Runoff in this area drains from west to east towards South Whitcomb Street at about a 2% slope. The area is primarily single family residences with grassed yards. Little or no site grading was completed when homes were constructed and runoff sheet flows through this area. No sideyard swales exist and the sheet flows typically run against the house foundations and then are either detained in natural back yard low areas or flow around the house foundation to the street. No improved storm sewers, detention areas, inlets, swales or other drainage conveyances except for the curb and gutter on Blevins Court are apparent. -2- PROPOSED DRAINAGE OFF -SITE FLOWS Runoff patterns except for a small area immediately west of the proposed site will remain the same (see figure 2). Flows to the Northwest continue to fun through lot 8 and into Blevins Court. Flows to the south and east continue to flow away from this site towards Prospect Road as shown by the contour mapping. ON -SITE FLOWS The runoff from the site including roof drainage and a small area of offsite flows is collected by grass -lined swales along the north and south side of the proposed structure. These flows are diverted to the parking lot which also is designed to act as a detention and sedimentation pond. An outlet pipe at the northeast corner of the parking lot will restrict outlet flows to the historic two year rate. This pipe will outlet into Blevins Court where flows will be conveyed in the existing curb and gutter easterly to South Whitcomb Street (see figure 2). The calculations for the detention pond are attached. Calculations for the runoff are also attached. They are summarized as follows: -3- �IIOP� I I � I I N 11 1-4 w Un FIGURE 2 Historic Q2 = .11 cfs Qioo = .40 cfs Developed 02 = .23 cfs 0100 = •87 cfs EROSION CONTROL The parking lot and building area will be stripped during construction. The back one- half of the lot will remain in natural grasses. Due to the small size of this project all of the improvements will be built at one time. Water erosion control will be accomplished by the placement of a sediment trap at the location of the proposed detention pond. Wind erosion control will be accomplished by existing trees and grasses at the west edge of the site. The construction will be completed during the summer of 1992 at a time of low wind potential. More detailed erosion control calculations and schedule are attached. CONCLUSION The construction of a duplex on this site will have little impact on drainage flows in this area. Runoff from the west will continue to sheet flow easterly through the area. A small amount of this drainage will flow into the proposed site. This runoff along with the on -site runoff will flow via grass -lined swales into the parking lot / detention area. The parking lot me provides 1150 cubic feet of detention and will release historic runoff of .11 CFS through a 2Y<" pipe in the curb and gutter. This outflow culvert runs into a 4" PVC outfall pipe and through a sidewalk culvert before entering Blevins Court. It is anticipated that the .11 CFS historic flow will have minimum impact on Blevins Court street flows. An overflow elevation of 13.14 is established at the entrance driveway for the detention pond and any overflow will discharge through the driveway. -5- RPARSONS & CLIEN 71 n��% eGI�VYr JOB NO. W d �zy ASSOCIATES PROJECT `�+ t/ILUI�IS CG� V' CALCULATIONS FOR CONSULTING ENGINEERS S MADE BV���/' �DATE I-15-12 CHECKED BV DATE SHEETOF Ft. COIIiI , Cobrsdo 80524 �z{P/mfnP �om�©31�e ' C I Lind 0Se rail Esc hit " fi 4clf d% �. W Pu(l1,� 2717 0,00 2R � (� oft IJ-f 0• aoy 1•3 9 2ur I,So6 0.03y Itt7 9 Lgncl3CvlpAili 2-312 0, 1W ILL Z Telali 1, an lad.o% Wer9Lilcs "C y7 /oo 915 o/r7 �uno f f t,,cjl�j Cae ,fioj - levii Tc -! 20. (l Za Tcrvo 487 (W) - 115 Z)) No. 7 1r1 b 16 Fam 3-1 T z = z, os a f+ r�va = 5.72 Q c{ c Tl} aloa �I zs)(•z) l� yz)(•z)) _ .10 IFS