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HomeMy WebLinkAboutDrainage Reports - 01/01/1981�® TARANTO, STANTON & TAGGE mile CONSULTING ENGINEERS -FORT COLLINS COLORADO sr...+o.+ January 12, 1981 Re: Cimarron West P.U.D. CONSULTING ENG11 City of Fort Collins 300 LaPorte Avenue Fort Collins, Colorado 80521 Gentlemen: Enclosed is the drainage report -for Cimarron West P.U.D. for your review. Exhibit "C" shows the routing for the two (2) year and one hundred (100) year storm which is in accordance with the City of Fort Collins "Storm Drainage Design Criteria". If you have any questions concerning this report, please feel free to - contact our office. Very truly yours, ' Rick R. Pickard Larry E. tanton, P.E. TARANTO, STANTON & TAGGE i CONSULTING ENGINEERS 112 W. 11TH AVE. 6412 S. COLLEGE AVE. P.O. BOX 703 HOLDREGE, NE 68949 FORT COLLINS, CO 80525 HAYDEN, CO 81639 (308)995-6677 (303)226-0557 (303)276-3834 TAB1,1: OF CONTENTS I.. INTRODUCTION II. AREA OF STUDY III. DESIGN CRITERIA IV. PROPOSED STORM DRAINAGE. SYSTEM V. CONCLUSIONS AND RECOMMENDATIONS VI. DESIGN CALCULATIONS LIST OF EXHIBITS EXHIBIT A - Area of Study. EXHIBIT B - Rainfall Intensity Curve EXHIBIT C - Proposed Storm Drainage System DRAINAGE REPORT FOR CIMARRON WEST P.U.D. Fort Collins, Colorado I. INTRODUCTION The purpose of this report is to outline the methods for conveyance and disposal of storm water runoff for the proposed Cimarron West Planned Unit Development. The project consists of multi -family units, including four unit condominiums, two unit condominiums, four-plex apartments and twelve unit apartments, with a total developed area of 16.66 acres. The project will include improvements to West Drake Road and South Shields Street. Items to be covered in this report are as follows: 1. Area of Study 2. ,Design Criteria 3. Proposed Storm Drainage System 4. Conclusions and Recommendations 5. Design Calculations r II. AREA OF.STUDY Exhibit A shows the project site. Cimarron West is located in the Northeast Quarter of Section 27, Township 7 North, Range 69 West of the Sixth Principal Meridian, City of Fort Collins, Larimer County, Colorado. In general, this site is bounded to the north by West Drake Road, to the east by South Shields Street, to the south by Rocky Mountain High School, and to the west by Ken- sington South Subdivision. The only offsite_drainage,to be considered in this project is that of South Shields Street. In conversations with the City of Fort Collins__Drainage Department, we arrived at a suitable size for the inlet intended for South , Shields Street. All other upstream basins have been intercepted by previous developments in the adjacent areas. �//'_ / Lac e Stu ou G� 4lel .44 � oo Y5,tvt � d' �� �� alrude� �.: �xa� ale ��s�,� i�c,�ef � � to VG2 fln C I MAR WEST FORT COLLiNs COLORADO VICINITY MAP SCALE: I"= 2800' F-,v. 14 15 8...�_}i4 ^3.�'iT+5in'�`�."f,"�' <'="+`�`.%: . '..'rae;r'y�..'yg"'e•-:s.F�`+y9.5�i..'".;'>9 t aPC FF'F>xsY'Hv.+::" x:�L s ., �+r`;- 'rC`.f"^". �. v»M:?�.'vw,.: .:n-. � a-:v III. DESIGN CRITERIA The design criteria for this study was based upon the Denver. Regional Council. of Governments "Urban Storm Drainage Manual". Because the overall drainage basin area of the site was less than.200 acres, the Rational Method can.be used to evaluate flows from the site for the two (2) year and one hundred (100) year storm for both developed and undeveloped conditions.. The Rational Method relates runoff to rainfall intensities by the following formula: Q = CiACf Where: Q = Maximum peak rate of runoff in cubic feet per second (c.f.s.) C = Runoff coefficient in inches per hour. "C" is the ratio between the maximum rate of runoff from the area and the average rate of rainfall intensities for the period of maximum rainfall of given frequency of occurence having a duration equal to the time of . concentration (Tc). i = Average rainfall intensities in inches per hour for a duration equal to the time of concentration. The time of concentration is the time required for water to flow from the most remote point of the basin to the point of interest. Cf= Frequency factor which is used to account for antecedent preci- pitation conditions. To be used when determining runoff from storms that occur less frequently than once in ten (10) years. Recurrence Interval Cf, (Years) 2 to 10 1.00 25 1.10 50 1.20 _ 100 1.25 The runoff coefficients used in these calculations were an adjusted value which reflects the degree of imperviousness or perviousness. The coefficient reflects the effects of infiltration, detention storage, evaporation, retention, flow routing and interception. Recommended values -of "C" values for various descriptions of land use were provided by the City of Fort Collins Storm Drain- age Design Criteria Those used are as follows: Runoff Description of Area Coefficients Medium to High Multi -Family 0.65 Asphalt Paving 0.95 Unimproved Areas 0.20 Lawns (Flat less than 2%, heavy soil). 0.20 Note: For the "C" value to be used to determine the times of concentration for runoff, each surface was evaluated. For example when flows were overland (lawns), a "C" value of 0.20 was used. When flows were routed through streets, a "C" value of 0.95 was used. To evaluate the peak rate of runoff for the developed conditions, a composite "C" factor of 0.65 was used in the Rational Method formula. CiACf - [ Rainfall' intensities were based on the intensity curves as shown in Exhibit "B". No Text I\'.. PROPOSED STORM DRAINAGE SYSTEM The overall drainage plan for the site is shown on Exhibit "C". Initial two year and major one. hundred year storm flow routes are shown. The inlets; catch basins and outlet conduits have been sized to allow both the major and nuisance flows to be conveyed to the drainage swales and detention ponds. The site historically drains to the north and east with a natural high point located in the north central part of the project. Therefore, our drainage system of swal.es, parking areas, landscaping and public Streets uses this natural drainage to its advantage in providing a safe and efficient means to control storm water runoff. FM The site has been broken into two (2) major drainage basins, Drainage Basin A and Drainage Basin B. Exhibit "C" illustrates their boundaries. Basin "A", 4.59 acres, drains to the north into inlets A-1 and A-2, with openings measuring 5.5' x 0.5' and 3.0' x 0.5' respectively. A fifteen inch (15") Reinforced Concrete Pipe (RCP) carries the two year and one hundred year (as previously mentioned) flows to detention pond A-1 where it is released at the two year historic rate of 1.07 cubic feet per second (c.f.s.) The runoff from a small portion of Basin A is allowed to enter a grated inlet measuring 3.33' x 1..92'which is located in the open space adjacent to West Drake Road. This runoff joins flows from detention pond A-1 and proceeds to an existing detention pond in Kensington South via offsite storm sewer OA-1 and an existing drainage swale adjacent to West Drake Read. A previous drainage study. done for Kensington South Subdivision has provided sufficient detention volume and release capabilities to include Basin A. Therefore, runoff from storin sower line OA-1 will enter the existing detention pond to be released by the twelve inch (12") CMP outlet pipe then on to Spring Creek. Basin B, 12.07 acres, drains to the east into inlets B-1 B-2 B-3 and B-4 with throat openings equal to 5.0' x 0.5', 5.0' x 0.5', 3.0 x 0.5' and 3. 0' x 0.5! respectively. Inelts are sized to carry the one hundred year and two year storm to prevent curb topping. Inlets B-1 and B-2 carry flows by means of a drainage swale and fifteen inch (15") storm drain to detention pond B-1. Inlets B-3 and B-4 carry flows directly to detention pond B-1. Storm runoff which is not picked up by parking areas or streets but rather travels overland will be intercepted by detention pond B-1. A fifteen inch (15") diamet-rr storm sewer carries the two year (historic) controlled discharge from detention pond B-1 to an existing flat bottom drainage ditch located to the east.in Cimarron Square P.U.D. From this point, a forty-two inch (42") storm drain conveys the runoff to a detention pond in Woodwest Subdivision. A previous drainage study has provided suffi- cient detention.and release capabilities to handle discharge from Basin B. Drainage slopes throughout t 'the project site as a rule, are not less than one percent (1%) to insure proper drainage, therefore eliminating any possibility of ponding. V. CONCLUSTONS AND kECOMMENDATfONS The project site drainage system was developed using the historic drainage as a guideline. Basins A and B drain to the north and east respectively. Parking areas, drainage swales, landscaping, inlets, storm sewer and streets provide a safe and efficient means of conveying the two year (nuisance) and one hundred year (major) storm flows. There will be no curb topping as a result of the sizing of each inlet to carry the one hundred year storm. We feel the drainage questions.of this project site have been answered and any offsite flow contributions have been taken into consideration. We recommend the above described storm drainage system built in accordance with the utility drawings prepared for the site. If there are any questions with regard to this "Storm Drainage Report" prepared for Cimarron West P.U.D., feel free to contact our office. Respectfully submitted, Rick R. Pickard TARANTO, STANTON & TAGGE CONSULTING ENGINEERS CLIENT JOB NO. - - BILy GL! GG1Mkdd1 iYpp[[ii1166[[11 LL;1[p7 TA CANTO• STANTON A T&G[ CONSULTINGE NGINEER{ PROJECT CALCULATIONS FOR FORT COLLINS. COLO\ADO / 1vYi1 ,., MADE BY DATE CHECKED BY DATE SHEET / OFF,.(_ _wtil:��; C/ovLS 0_--- �� ! i • t i I I" i i �i -, i I i •" - I t C -F s I , i � �•- • I it (`�� I I I" � � i � i i i _ L z 3 x 3 /¢, rQo sF �I- � I -1�h•ThJ b f/_".�`Q S _ �I YlT [. �+o1Jp �I_�iq, I I I - I d dI - I l200,'o3.�i'lo J —I - �5� 1 3 �o a7� If 14, ono. + I+, 90 4.� s ��__%5(�-< - - ° I }' - -- - I. _ I I I i I I i ' -r.. - - _ .CLIENT / �`"/. 9"' ✓l[�'! JOB NO.- pi- ,� TARANTO. STANTON A TAGGE Gj�. 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STON l TAGG[ — CONSULTING IocIr.[[[[ PROJECT CALCULATIONS FOR ro.i COLL40S. COLORADO MADE BY DATE CHECKED BY - DATE SHEET—- L_OF c.h-f�__._ GIrf r61) -- -- - - ' I : I I ! _ 1 i Jg I _ i 2 , LeD ! 1 , Lp i -- -=—' I - ! J, i j6Z.-j. I ;--I-_w.ZoLiJ-z�S�L_.5l�:0_•4 I - -- - - -- ! -- j - --I- , • � � � .o ,- x. � a�i� I - o se I I I 71 Lo•j j 1 _ I I I I I -{• CA , { 1- ,. I----00.1."1'S J1f`3eoo� I . � ��l0��1!3 .���.. j ;__ z'41•��-0_�:.". t i ' i ' CLIENT JOB N0. TARANTO• STANTON A TAGGR CONSULTING RNG:NCLRS PROJECT CALCULATIONS FOR e[�Y� IOfi COLLINL. COLORIDO ,2 i �4i� MADE BY -DATE -CHECKED 8Y DATE SHEET'r, OF_ I 1 i I i 7.?_._'Pnd= i f , ,_. To�a'I ►'�,(ee, _c�.- ----!-0;/q- 1 is i .Ca!'V ._Vmll ._i_A�a;/ ! /�Iv//:d ! 4 - /i —j-_ ! i--� I —� I GogJLoL%c I i_ Zr� �Pry_�t.� ---./4/ft°cL !-- — '— { ✓D • 3 ' i' , , i I"! I I I !L I — — ' ,——_ ,_ ! I .-i. t I' I i oD .,__�.' l�o_�-�----:----;-. l.i—,_ _� ..--,--- 3r z-�c;yo� I z18���. , �_i-1.4_�, �•.� �: PL _ ;�� i' 9 -1 i! 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NO 1/0 r It I-77 I I I I , 77 Iclo!Ill .G�°CL,._✓sa �i ron% _� G� . ! _ i s ...I i � 6 ; - ! J�g.S I ! I � _ � d =� Q•.1 0' - i . , � I I . � i ! _ I I •.;- I I � ` "� - I to .3 l 1 o(Q J_o —5� -- 12 - I ! � I •.! I 1- j y-t % ._ I,Ol I I o• z� 595 Z._._._! 4o•a.7 + !1 8 l LII 1 D:-aS�,.__¢I n.i._ zto.3Z I If , .� . 2,: •- . 1: 4 _ ; o o � .J ,«. _... a-. -L ...ez CLIENT JOB NO. can TAEANTO. STANTON JI TAGGE ' 1kF°i7//�°CCJJy9 CONSULTING [NGIFEERL PROJECT CALCULATIONS FOR IYET COLLINS. COLOEA00 MADE BV DATE CHECKED BY DATE SHEET OF I i 4 I I Io,:9S - d, - rro_:_ ;_ ;dam aa5, ' �3 : -! ?�&s 1�3 -D.lvo%. S =} 1. 3Q�'/o; _S¢.! 1�:5'¢ �'0 3j_I_L7r1 Ism I- -- - - - 01-- -- - - _ -1 - - I -y-- AL ko_ ! 1 I I I I I I n r I I I 4.a5 �- I_-�- --1 -- 710 i I - 7 I 1 I I ! I -_ T + ! 1 I —?G3' �q- -- I— - -I i I iit Wa !�-IP' .! I- --tom 'too:.Ml2.1ooil -- L:--- I I I I I l I ..�-r! -S--.GcF�A - I I. c t : I ' r� 1 , CLIENT JOB NO. gAe TARANTO. STANTON A TAGG[ CALCULATIONS FOR Lg' CONSULTING LNGINLLO PROJECT ivy /OAT COLLINS. COLO11400 MADE BY DATE CHECKED BY DATE SHEET ' 2 OF 19 • .._ n [1 q GNH T - Ino ' T ' e I ��7 C. 1 - - i I � i i � I. i� i i ' O I L.-._ i I_ I • LJ 81- - I I _- -I I- ' , 1 : • 'f'� (e o m-, Al � � - � I t � •I I , ' I I �� r I 5!U Wt M!L_M_, l< -, 77 --- ! (. A. T I j r 17 1 I: y I- I .•._"1'—I - i .!_. i I - I � I I i.. , 1 '.- ' .' L._ ._ .� _. - I ( t 1 _ �— - r .._-..4.•-r� .- .yam_ . "" :{... K,. .Y :_.� - CLIENT JOB NO. Fo - TARANTO. STAM OM & TAG [ � C SUL rING LNGIN akfi ROJECT CALCULATIONS FOR 10 T CO.LIML COLO APO ADE BY D TE CHECKED BY' DATE SHEET 3 OF�_ : in QD i 1 �,co a ---. t7 O I I I j i ! I ; I � I 0 o o. 0 0 { -- - - -- a � -- ' - --I- -' - - --' ' I 1 n i t , _ j---I- KI I �}----' - - - - — -- In N=�N�, 1 in I I I ' e I _ e _jr) _o 1 I ' I I ' --; -- -- —t I I Q j CZ2 I vI { I 1:bb-S'£-� ._1 jr y 1 j 9- 1 -71 �a3i c� I i I I 1 006 ■■ CLIENT . �,�� JOB NO. - �� TANANTO. STANTON • T.LGG[ ,+fir , wp 3 -. CALCULATIONS FOR � W'NA/�Pi irJ�l CONLU LT,NG [NGI ME[YL PROJECT g WONT COLUNL. COLONLDO �,�,p - I. 3V� MADE BV�DATE CHECKED BY DATE SHEET— OF cl-- — - l r II r , GJN out `# I ` SNrev✓A./. i _ ti' A-�eitW--�--!----�ol---a---� , I I' I i 3i I i- o�0 _ Z . O j r j .: i i I - • f � l , - -L_ -�-__ j. _ i -_-� j __ i __•-� ! _-, I �(pS�iZ 5.5 ' is ._ 1-4 • _ l 11 I '.:j Lam__: -I—__—• ln, c'J� �- ----� —�— i -..,- -;- i � I , i I ,. 1 3?0, 15'v.,. j i I C 9 5 b3 0I' 1 i !Ct3,s' 7� _ ►3 5p 1 e,IZ qp 3 t¢ 9 L' I I r �► r s i i ? (f - j I ,� I j I�i_ ... I-- ._ - -._I_.- i .. t9 (_a-._..0 ���4 (_/i _ _S`L•. nt�. i I , I : No Text CLIENT JOB NO. I TA CONTO.STANTOM TCLGL - 5Lif4N1 CANTO. ST6ION AEELL PROJECT CALCULATIONS FOR /Q,LI COLLINS. COLOL.00 MADE BY DATE CHECKED BY DATE SHEET • OF- 1 I ' 1 Y i 7r✓ _4 z s-J .v l%a• rcdn4 _ sh+ 11 R!2e�m,��,rh.d: use inrl. 5 1 14. lr 1be Met 56 Woo 3 JA i '' � i cl` -l�_zo .I ` icy= �:.1s l --' 43!_ Os•._g5 I I s�__L.00- � '-�-..--'S � .,/-•sa; .._:_ 'Sad_= !'°d I_ __ � � �: I _ I — a , ---- 2——4-_.-...!�e�onjmP.vj(� vsl;r� S.� D•$;' !� prr.�H (JJC'a✓�ilG..i- LB,S _...c,!�5...- I , i No Text