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Home My WebLink AboutDrainage Reports - 09/18/1992I 3�a �� b � :-�-�,I caP� � � ` �►�� , 1�ev�ewe.d • Finai A proved Report Date � � �� GREENBRIAR PARK City of Fort Collins, Colorado STORM DRAINAGE and EROSION CONTROL REFORT Ju1y 10,195►2 (Revised September 9, 1992) Prepared For: City of Fort Collins Stormwater Utility Department P.O. Box 580 Fort Collins, Colorado 80522 Prepared By: EDAW, Inc. 240 East Mountain Ave. Fort Collins, Colorado, 80524 Phone (303) 484-6073 Fax (303) 484-8518 September 9, 1992 Mr. Glen Schlueter City of Fort Collins Stormwater Utility Department PO Box 580 Fort Collins, Colorado 80522 Re: Greenbriar Park EDAW Job No. 1F565.02 Dear Glen, EDAW is pleased to present the attached Storm Drainage and Erosion Control Report for Greenbriar Park. If you have any questions, please call so we can address them promptly. Sincerely, 0�`( A L Lq� L ,.. C�J' J"�� liJ��C:��' /< i� r i� \•`" ��.': 4 1�1 �"�'�-y��0 � �:"U: Gregory A. ' ��( P. ``': `�' ,.: .� s ; � � ;: FIlDCl� Ja :''� ,.., ��r r�' ° O � °F �c�i.asav Attachment GREENBRIAR PARK City of Fort Coltins, Colorado STORM DRAINAGE and EROSION CONTROL REPORT July 10, 1992 (Revised September 9, 1992) INTRODUCTION The City of Fort Collins is proposing to build a 22 acre park off of Willox Lane in north central Fort Collins. This report will serve to analyze the physical characteristics of the site which will deternune the temporary and permanent impacts to the surroundings that may be anticipated due to construction of the park. This report will predict the magnitude and consequences of storm runoffs and will recommend means to prevent and control damage from erosion and flooding. Erosion control will consist of ineasures initiated during construction. The report will address the following: 1. Site Description 2. Storm Drainage A. Design Criteria B. Hydrology 3. Erosion Control 4. Summary of Storm Drainage and Erosion Control Measures It is intended that the recommendations found in this report become an integral part of the design and construction phases of the project. A Vicinity Map follows. -1- 1 Vicinit Ma - Y p TERRY LAKE e WIL�LOX CONIFER �a ST. a w � � 0 U z �-i11: _�:Ii�.�:�•�lf H � A o GREENBRIAR A PARK W SITKA x ST. ..� ��.� : •`q,�,ti' ,�� '� •� • � ••� , � i .,��h� d � � z � � � �o s��.t� Y l� � STI'E DESCRIPTION The Greenbriaz Pazk site is bound by Bramblebush Street on the north, Briazcliff road on the east and Willox Lane on the west. The southern border is formed by the backyard of ,,ti �_ residential lots along Grouse Circle. More specifically, it is situated in the North 1/2 of the j� =3 Northeast 1/4 of Section 1, Township 7 North, Range 69 West of the 6th Principal Meridian, Fort Collins, Colorado. The site is located in the Greenbriar Drainage Basin. The parcel is divided by a slight ��- north-south ridge which divides the area into two subbasins. Topographical relief is � approximately 8 feet and the average slope is about 3.5 3b . There are no pronounced natural drainage features on the site. _ -- --- -- -------- The historical drainage pattern is general sheet flow. The eastern 2/3 of the site presently sheet flows to the south and to the east. The west 1/3 sheetflows to the south and to the west. Recent house construction between Grouse Circle and the south property line of the park have utilized graded building pads to avoid runoff leaving the park site. Graded this way, each residential lot sheds each individual lot runoff to the sides and front and back of the lot. A review of the elevation contours and field observations suggests that some water may presently i by__the raised building pads. ,�/�u/ ,,;_ Offsite drainage impmvements immediately adjacent to the site consist of curb and gutter ��g on all public streets and culverts under Willox Lane which discharge street runoff, captured by ` curb inlets, into the slough on the west side of Willox Lane. Vegetation in the azea is primarily a prairie grass punctuated by several trees. There are �'� �Y �� no discernible "wetland" areas on the site. ,�%��; The soil groups maldng up the site are predominantly clay loam or clay. S✓ � STORM DRAINAGE Runoff from the developed site during the 100-yr storm will not be allowed to exceed that of the historical, undeveloped discharge rates occurring during a 2-yr storm. Runoff that is intercepted by swales or catch basins will be directed to a new pond for storage and ultimate use as irrigation water. The western portion of the site, which presently drains to the detention pond across Willox Lane, will increase in acreage from 7.4 ac to 19.4 acres due to regrading of the site. The increase in area, along with an increase in runoff due to developed conditions, results in a substantial increase in runoff (in this basin), to an offsite� detention pond that is approaching capacity. The increase in runoff from the developed park site will be mitigated by providing storage for the increased runoff volume. An onsite detention pond with a controlled release rate -2- � r � � i� � was studied. This detention pond will also serve as a sedimentation pond during construction, allowing water borne sediment to settle_ out prior to leaving the site. An existing culvert beneath Willox Lane will be utilized to discharge runoff to the offsite detention pond. The outlet will have an orifice plate to restrict the rate of runoff to the historic 2-yr runoff. At the time this report is being prepared, the City of Fort Collins is updating the regional master plan of which this site is part (Evergreen Park, Greenbriar Outfall Master Drainage Plan). A SWMM model used to prepare that report will include the effects of the Greenbriar Park construction. Preliminary analysis reveals that the detention being provided onsite mitigates any need for additional storage in the existing detention pond across Willox, and a letter stating that the pmposed park construction was analyzed as part of the Master Plan is included with this report �,,,� Additionally, the SWMM study suggests that sufficient detention is provided via runo�f routi� 4�`' through the proposed irrigation storage pond that the orifice plate�laced on the onsite detention pond can be removed in the future at the City's option. ��, In the eastern portion of the park site, developed runoff from 2.6 acres will be allowed to sheet flow offsite in the same patterns as before. Extensive site grading and berming w�l greatly reduce the area contributing to runoff in this azea, and no increase in runoff will occur. The result is no impact on the existing Greenbriar Detention Pond or existing residential lots. �`' It appears, however, that a conservative approach that improves existing drainage conditions � along the park's south pmperty line might prevent complaints from adjacent residents. Thia report will recommend that an attempt be made to alleviate the drainage risks that are already associated with the present topography. Suggested improvements will be discussed later. No permanent offsite improvements are planned as part of the project. This report addresses only the increase in runoff expected to result from improvements within the immediate 22 acres. A. Design Criteria The City of Fort Collins has prepared a Storm Drainage Design Criteria and Construction Standards (SDDC) which provides the basis for the analysis used in predicting storm runoff and the recommended drainage improvements. B. Hydrology The Rational Method is used to predict the amount of runoff. The 100-year return frequency was used in this report to predict major peak discharges. The 2-year storm event will be used to size and locate minor structures such as most drains and storm sewers. Whenever the 2-year storm is used for the basis of design, a provision will be made for emergency by-pass or overflow. The by-pass feature will be designed for the major storm. -3- ' �- � ' � � When the irrigation storage pond is at elevation 56. 8, the expected Normal Water Surface (NWS), the additional storage provided in the pond above that elevation, (the overflow elevation is at ele. 60.3), will actually result in a reduction in the amount of runoff than presently runs offsite. However, the most severe runoff conditions will occur when the design storm occurs at the same time the irrigation pond is full. This report, and the SV�IvII�i model performed for updates to the Evergreen Park, Greenbriaz Outfall Master Drainage Plan, conservatively assumes this situation. ' Rational Method runoff calculations are provided as part of this report. The eastern portion is shown to not increase runoff above the historic rate. Runoff from the western part of the s�te will be controlled via an orifice plate to mau�tam the histonc discharge rate. Since , the pond proposed as part of the Greenbriar Park construcdon offers an excellent opportunity to detain park runoff, pressure on the existing detention pond is reduced. I� I� I� Calculations require that 76,200 cf of storage is required to detain the increased runoff. The configuration of the detention pond results in a High Water Level of 58.2, resulting in a water depth of 1 ft. Because they are connected by a culvert, both the detention pond and the imigation storage pond provide storage. While full, minimum freeboard in the detention pond is approumately 2 ft. The area of minimum freeboard is located where the existing culvert crosses under Willox Lane. Minimum freeboard in the irrigation storage pond also is approximately 2', and occurs at the berm separating the irrigation and the detention ponds. As a result of the proposed re-grading of the park site, present sheetflow across the � southern park boundary will be reduced due to the reduction in area contributing to that offsite sheetflow. It is recommended, however' to provide a french drain along the south property line to intercept from both d'uections and provide an outlet for areas of possibie entrapment of surface flows. A french drain of perforated pipe surrounded by a bedding of very porous gravel will tend to drain any areas that might tend to pond surface water. � The measure is designed to offer an improvement to existing conditions which might be complicated by placement of fill during construction of the park. Removai of nuisance surfact water is the primary reason for installation of the french drain. In major storms, it is � conceivable that the french drain will perform a valuable service in aiding removal of overland flows to the storage pond. As the volume of water intercepted by the drain increases, the hydraulic gradient within the pipe, and the gravel bedding itself, will cause water to flow � towards the storage pond, even at 1,4 % slope. ' 1 � I� Sheets F.C-1 and F.C-2, Drainage and Erosion Control, are included as part of this report. -4- � t � � �, EROSION CONTROL � The SDDC outlines the causes and results of soil erosion due to wind and rain. The � SDDC shall be considered in it's entirety for guidelines to aid in preventing soil erosion. The SDDC will govern requirements and specifications for earth moving and seeding at the construction site. In accordance with the SDDC, Performance Standards were calculated then the Effectiveness of a variety of possible erosion control measures were investigated undl those Performance Standards were met. One primary element in the proposed erosion control plan consists of mulching the site in accorda.nce with the requirements of the SDDC. Because the site likely will be undergoing constant grading and earthmoving operations, continuous application of mulch may not be feasible. During construction operations, the disturbed areas will be furrowed by equipment and temporary wind bazriers will be constructed. Both the furrows and the wind bazriers will run perpendicular to the prevailing northwesterly winds. General orientation of the funows and wind barriers is indicated on the erosion plan. A second major element of the erosion control plan requires that the detention/sedimentation pond in the west portion of the site be constructed prior to any major ground disturbance. To prevent silt from leaving this pond, invert of the pond will initially be constructed to a depth of about 6 inches below the outlet pipe. Addidonally, ezisting catch basins in public streets bordering the site shall be pmtected with gravel filters (ciams) in accordance with the SDDC. Area inlets constructed as part of this project shall be protected from silt by use of straw bales or a sediment fence, completely surrounding the inlets. Construction sequencing and details for erosion control measures are indicated on the two drawings included with this report. The sequencing or timing of the measures are preliminary at this point and the actual construction schedule will determine the proper timing and measures utilized by the contractor. The contractor should have the option to submit for approval a i' vised erosion nt�l p� and schedule to better suit actual construction sequencin� and ✓ rpyogress. In addition to the Drawings, details and other criteria of the Greenbriar Park project manual and the City of Fort Collins Erosion Control Manual apply. -S- ' � 1�_;_� � � ' 1 ' • I ; • �1 ' � . � � ' � 1_ • _ J: The following is a summary of the storm drainage improvements and erosion control measures that will part of the Greenbriar Park construction. ��_ ' � � � � � � �,- 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. Keep disturbed areas to a reasonable minimum at any one time. Stabilize all disturbed azeas. Keep runoff to velocities not causing erosion. Retai.n sediment by filtering runoff and detain sediment-laden runoff for a period of time, allowing silt to settle out. Provide diversion channels to direct runoff around and away from disturbed areas. Keep all cut and fill slopes stabilized with terracing or scarifying furrows perpendicular to the slope. Protect all drain inlets and culverts with sediment filters. Protect stockpiled materials from wind erosion. Stockpiles are not to be higher than 8' . Permanent ground cover is to be established on all disturbed azeas. Areas to be seeded which have been compacted by construcdon activities are to ripped or likewise Ioosened prior to seeding. Provide a temporary cover crop or an application of mulch to areas to remain unseeded for greater than one month. Disturbed areas which have topsoil removed may require an application of fertilizer prior to temporary seeding. Mulch that is subject to windblow is to be disced into the surface. Inspect, clean and repair all erosion control measures the following work d.ay after each storm event. Additional erosion control construction details and specifications shall be taken from the City of Fort Collins Storm Drainage Design Criteria and Construction Standards. Sizes and locations of site improvements are found on the drawings. � : 1' � � 1 . • ffiSTORIC CONDITIONS BASIN SUBBASIN SUBACRES ACRES A Ah 7.4 7.4 B Bh 14.6 22A wCs .20 .20 RUNOFF 1.6 cfs 3.6 cfs DEVELOPED CONDITIONS BASIN SUBBASIN SUBACRES ACRES A Ald 2.8 2.8 A2d 4.6 7.4 A3d 7.9 15.3 A4d 4.1 19.4 B Bd 2.6 22.0 wCM .35 .35 .35 .35 .35 RUNOFF 5.4 cfs 13.6 cfs 27.4 cfs 27.2 cfs 3.6 cfs -7- I� � � .� GRNSCHD.XLS EROSION CONTROL CONSTRUCTION SEQUENCE " GREENBRIAR PARK YEAR 1992 1993 MONTH AUG SEP OCT NOV DEC JAN FEB MAR APR MAY JUN JUL OVERLOT GRADING W�ND EROSION CONTROL oi oue ernne — . < enmeter erner � itiona arners _ _ _____ egetaUve easures _ ::........ ........ . _ .. .. .._. . ,. . 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SY� =__7o,s so - - - - - _ .�_ ___ .. ._.T„�... �- - _- -'K=_ �_�.f�C4o,viS+.�(4�o S 4 4�,o�S �� ' �$�3 �• RFS .---� ,.� _ __ _ _ . � -,- !.-.;.a .� :� �. � 4 �.. �. - �}�..��i. .�� , ` d�+�..-� • t� � _ _ .1Q _ _ SR, � - -j- . x - � ``. -d .�_ �.�-.�.a . .r.��- 3 .. . k '1.'r."+�.. _ �. . � p s8_,z z_i� �� .� 5c` � i �p 5g• z= � � 4,� ' , '_ � J�A'++�.� �i ��R. ~� 2/ �j 'S` 60 5+ 5 Sb� l i� �.bDS��.,�') � 1� � ZDd �9'3 _ _ _. -- - � Vo l � �„� = � i�'��+v' �t- - - - - - - - --.- - _ . _ . ,�;�' �o�v � ��c4 = _.�L 21� � r� 5 �� lC�'�'! -�; ; ; - -- _ _,�-- - - - � �= i , �--- � -- -- �, - z --�-- _ _�._ _ ___ _ _ __ .. � n DETENTION POND VOLUME REQUIREMENTS PROJECT: CITY OF FORT COLLINS GREENBRIAR PARK JOB NO.: 1F569.02 DATE: 11�May-92 TIME: 02:52 PM STORM: 100 YRS AREA: 19.40 ACRES C: 0.35 � Cf: 1.25 RELEASE: 1.6 CFS TIME INTENSITY RUNOFF RELEASE STORAGE (mins) iph (Given) (cf) (cf) (cf) ____________________________________________________ 10 7.2 36666 960 35706 15 5.85 44687 1440 43247 20 5.2 52962 1920 51042 25 4.6 58564 2400 56164 30 4.15 63402 2880 60522 35 3.8 67730 3360 64370 40 3.5 71295 3840 67455 45 3.3 75624 4320 71304 50 3 76388 4800 71588 55 2.8 78425 5280 73145 60 2.6 79443 5760 73683 65 2.45 81098 6240 74858 70 2.3 81989 6720 75269 75 2.18 83262 7200 76062 L C--�-��- -lr'�.� 80 2.06 83924 7680 76244 ��_� 85 1.95 8440$ 8160 76248 �� 90 1.85 84790 8640 76150 �` �`�, 95 1.76 85195 9120 76075 ' 100 1.68 85656 9600 76056 105 1.61 86089 10080 76009 110 1.54 86267 10560 75707 115 1.48 86674 11040 75634 120 � 1.42 86776 11520 75256 � �Ro�n The�E �-z �f c�T�i CRIT6T21A n �� 4Z J �� ,� �s-�z � II �"�M•1 � ��Ev�l, o ?�-D I /�lt, `' Z . �, J �= 7 10 S = a1'�i' ` •4 `o - _.�'`�_ �• 9��.i -.(.3�� •t5� v'toyz ,A�� -��g�_+ �� = 38 ��= ql.W, � �� --_ , 5� � - 3' s , Q�oo v�� ' 1. 2 S(. 3 ti� 3� ��Z. �� = 3. 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K _ � ,. �� n � (� � �J � � r � .�u- , , ��I( , � ' � G�'�`,�" ``, �� ,�' ,�e�r�-e- `� � .,�,�,� �. � � �-�-/� �- �� " � , - _ , r-r.<-vt1, l��- ��'`e-lf,ce^-�✓L�'� i��'�^.'L- � � � � ' � �� RAINFALL PERFORMANCE STANDARD EVALIIATION PROJECT: R,�u �t, �,q.-R,,, �-Z�L STANDARD FORM A COI�LETED BY : JP�M DATE : b L DEVELOPED ERODIBILITY Asb Lsb Ssb Lb Sb PS SUBBA�IN ZONE (ac) (ft)� (�) (feet) (�) ($) A,. . . �s��,,� z�4 s� ►.,�. M�o ncn 4�G A2. 9.c. �ioo �.�4 � � �� 70- s7,t) A 3 „ � �.9 �va ,—t i�$ Sqo �4-s�t �q �� 4.� s : �.�� 2.c, �� .q _� z2.o 'G1o_ 1.4� 7�.� , . MARCH 1891 8-14 DESIGN CRITERIA � � � � EFFECTIVENESS CALCULATIONS PROJECT : �,a � ur.� .41L� STANDARD FORM 8 COMPLETED BY: I�� DATE:. Erosion Control C-Factor P-Factor Method Value Value Comment �canvs Pt.w.�.a� , ,o i � . o _ , �� us� ro �. o .°1 ��.. �' �b�rL �vr�e��J l •v . S . � Nwv� .Dlo , i� 0 MAJOR PS SUB AREA BASIN ($) BASIN (Ac) CALCULATIONS A t�j .gc " Tontt � Z Z 1•9 �►�o�o P�i�..�,,�,.��W a.1 k b 20. 2 A��. � ��,1�,. • � . l� C = l.$ (.o�> } zo,z(,a,�- . Z Z • O (o � cNfi� P= �. 8 C�l } zo � C�� '�- �.� � — Z Z = � ` 54°�� ,_ �.o� x ,> �o �k�9�� J � Gi SS u,�,�.� .�.�.�.✓� S.� Sm*� rp� . � n MARCH 1991 8-15 DESIGN CRITERIA ' GRNSCHD.XLS EROSION CONTROL CONSTRUCTION SEnUENCE • GREENBRIAR PARK YEAR 1992 1993 MONTH AUG SEP OCT NOV DEC JAN FEB MAR APR MAY JUN JUL OVERLOT GRADING WIND EROSION CONTROL oi oufl ernny ; — enmeter rner __ . ..:::. .....,_; ... . .....,..:. _ ,..:::. .:. rtion rners egetaUvs easuror ;:�;.. ; < .::.::..::..: ...::..: . . �: .: ................... ............:.... :.......:.: .:..:...:......... ........ ____..< .... . .. .. Soil Sealant Other RAINFALL EROSION CONTROL STRUCTURAL e iment rap sin ? ; ; :: -. . . n et � ters _ _... traw arners ' ' :< < it ence rners , .. an ps are oi r aration QP :. �::. �:::: •:: :•::::::: :• . .,. ontour urrows ......:......:.:....:.::.::..::. ........................................... ....... .......................................... _............ . errac��q sp t oncrete av�np Other VEGETATIVE ermanent e enUnp u c ny ea ant ><;:zz:::.»>:> emporary e ant�np Sod Inatallation N etti ngslMate/Biankete Other NOTE: ' CONTRACTOR SHALL BE RESPONSIBLE FOR SUBMITTING AN EROSION CONTROL PLAN, CORRESPONDING TO THE ACTUAL CONSTRUCTION SCHEDULE, FOR APPROVAL BY THE STORMWATER UTILITY BOARD PRIOfi TO CONSTRUCTION Page 1 �� N N N � N O O �r r" ^�� nrn �i � � t /� ! � � � � � � � � i� �'��S�ZI�� <<-,�� y �U' c� i � « ;_� � � cQ. �a-� Ir l� C� , -� �� _ C,��-� � c�. c� . Dvpr �foc� CpZ, 5 �, U��.bl� _ �-5 . - �f� Q 5� ,3 (7�a� F o� � z, S �, ��I�.b te= 3. Z . ,-z ��, z `�2�-, . � 7 `�o�,,, �lc� 5- 3� c�., /�n a,,� �i��O �e �• B� �.� I�r G, F�.��= ��Ps /r-� Z �r� CJ�v--� l...l � ��'_i C'vT �G^c.x+� �L (� � Z. —_""""__.�_��,_ '� � s l vu ►� h f � 1 Sa-v� � i� C�.) O�, �� I� 3 iJ � C�/ �Cf-..��. � t . � �1 �'.�'' — -- - _ �-_ o 1 Q �� c o 1� � o CJ�.S = � �� V \\ U,�- Qr��iw EQtJ ��o �c1 `, -�j_ r�'4- Ucc�a��^ ' - ---- _ �—�� -�l �� Q �la6�e. --- -- — G� w+ � � , � � �,,. - - Q � �q L z� � T�>.(,�.Q c. =,� � , � i � `C.�= . (o ��•Z> �a,i � ��P�.� / ,$ �u�1o�, r�l` �.'� c�s� l " ' i�" --- - � �Du � � � � � (i e�� A � � ` �, �£ ��i o� y,�� L �.4�� O K . ��..� P� � �� s' � o .� s%> . �r� �, � .o ► 3 / �l3 ��z3 z� � Q'' ��L ` �� A •��S � �1•4a(.. �I.i-�> �po'a = t;,�� . ,oi3 � 3.q� ° � � � '�'�1v�,,� (. p.i,-� �o [ s , '�,`, 5 � � ��;- t...� � 11 _ c� � �_�c _ o� (�n-}L� �Vef�octiJ pCCv(S � �OO �f - �"ib►'�� , D��lc�.� �ow� �4 ZcQ = . G�t.,.>�Zl - �.{o, �i��8� = `11.2� c� ,��; ' r�� .��l,or� Q�� 13.� c�rs ��f�� c�.��lt cs«�,t G,�,, c9 6 v �. r��vcv 1-1 ia -�j -� r a e��cQ . � 5ww,v.•1 ��,-�ys�� .��.�a.kl�►��ia G��. (t�.�.,�, no ��bb I�,,,,s ccsu�fi, (� �.��1�� ite � w�� 1-�� 5 +f P f�a,r �-� . �o•�,� - I•qeb ��z3 12�3 �,z.3 .� ' to , Z ✓��, . � � � o� � �3 I � 3 '3 ` � � r��C� � 10+,.> GO�,�� t ��o� �� 1.� t Q.'� C�^�fo� :� m� ` �' � � � • � � � July 24, 1992 ' � 1 LIDSTONE & ANDERSON, INC. Water Resources and Environmental Cansultants 736 Whalers Way, Suite F-200 Fort Collins, Colorado 80525 (303) 226-0120 ,• Mr. Glen Schlueter City of Fort Collins Stormwater Utiliry 235 Mathews Street Fort Collins, CO 80524 Re: Hydrologic Analysis of the Proposed Greenbriar Park Grading and Drainage Plan � (part of LA Project No. CO-TST-05.4) Dear Glen, We have completed the requested hydrologic analysis of the proposed Greenbriar Park grading and drainage plan in the context of the Master Drainage Plan for the Evergreen Park/Greenbriar area. This letter provides a brief summary of the results of this analysis; the details associated with this analysis will be�included in the final Master Drainage Plan and will be incorporated at the time we address any final review comments you and Bob may have concerning the master plan. It was found that the proposed park plan directs runoff from an additional 12 acres to the proposed Pond 1; a tqtal of ZO acres when added to the original � 8 acres. However, all but 4 acres (of the tota120 acres) drains to the proposed park irrigation pond. Allowing for the require� 1-foot �: freebca.*d, th�re is a�praxu:��t�l�r 3 ac= � o: �:c: emental stcrage 3vaila�le in this pond (above the outlet culvert invert elevation which is 0.4 feet above the normal high water surface elevation). Accounting for this incremental storage and the proposed 15- inch outiet pipe in the SWMM model, it was determined that: (a) the irrigation pond uses 2.4 ac-ft of stora e thereby leaving more than 1-foot of freeboard, and (b) the required sto.rage in ond is decreased by 0.2 ac-ft. Due to the reduction in drainage area to the .Greenbriar ast Pond, the required storage id that pond would be reduced by 2 ac-ft. In � summary, the proposed grading plan for the park would not adversely impact the results kj ontained in the Master Drainage Plan. �oY 1f/�j`/ryq% . . / / � Branch Office: Box 27, Savery, Wyoming 82332 Mr. Glen Schlueter ,• � Page 2 It is noted that the impact of the proposed detention pond in the park was not modeled for ihis analysis. Based on ihe results cited above, it is not required for storm drainage purposes and does not need to be included in the iinal pazk design. Conversely, it should not have any adverse impacts on storm drainage and therefore may be retained in the final park configuration. Please call us if you have any questions concerning this analysis. Sincerely, Gre . Koch, P.E. � Senior ngineer cc: Mr. Steve Humann, TST, Inc. GJK/tlt 0 0 � u � ^/� �✓. Curb �n�u� ._ _ r � _ C �� .ir,97% I � r�i� tx�'4�,�jtt�"s`��?�'f �q Wire S�:r¢en — ter) iAppr�r +'i'Id�esh) WiroScreerr-� �rovei Filter PIAN VIEW �verFiow —^1 �f�llered Wat.er Runof� /�i —�„�.,.,,_ LEGEN D WireScreen—� t��'�� I �I �Ii. 2''x4"Wood SLud �-�rb Inirt s�cnoN n-A OFFSITE STREET FLOWS c��Notes: NOT IMPACTED 1. Inspect and repair filtors aitor unch stormevent. Removosodimontwhun BY CONSTRUCTION one half of the filccr dopth has boon OF TH I S PROJECT tilled. Removed sedimont shall bo da- / posited in an area tributary to a sodi- ment bas�n or other (iliorinp monsiuo. 2. Sediment and gravol shall bo immodlntoly / �moved from travclod wuy ol ruudn. / CURB INLET FILTER GRAVEL . � / � � � \ \ \ \ \ � \ \ � �E � �vE � � ._ � / �, 3�� A-3� �L � t ''s �r��r, P��c-e ��(� � ro ��FE �A�L � i • ,l �ourt C�> �io�-t �1� � � �F-r�,�,c, -ro RA�� M�p..� h� ��.oY3�E 58 �,; RErtcv�� IN FU7ul'�-E t7y�.��+,v¢�� 1� �-c ci��:: ��-�c�ta � y,P� ORIFICE PLATE DETAI� �/ uo s�-�•� E iTyG9u�►L Dh•iG P�-/��-�L' n "h"ISTORIC CONDITIONS BASIN "A" Ah Area (Acres) �.4 ' Release Rate (cfs) � j B A SI N�� A�� A d NOTE: ALL PARKING LOT Area (Acres� 19.4 SPOT ELEVATIONS ARE TOP BACK OF CURB UNLES� Release Rate �CfS� 27•2 LABELED FL(F�OW�INE /^ � "d"EVELOPED � CONDITIONS ' i � �% � � Y / J � \ \ � / � , X �/ �� , � � / , x � � , / i ��_ � � i -----�_ I I Bramblebush Street � I I I 1� I� \ \ � � � General Noees: 1. Wedc�c loosc straw betwoon thu s�nknd bales. � 2. Inspect and repair filters ultar oach storm event. Remove sodimont whc:n onc half ot the filtcr depth has becn filled. Removed sediment shall ba deposi;zd in an area tributary lo a sediment basin or other liltorin� rnoasure 3. Sediment shall be removad immadi[nuly from traveled way of roads. Area Inlet w�thGrate V O C] G1 V _ C � � �� '_= y ' a -_ � �) � � =__- .— � u u ❑ u .--+�rjT' ��-- r+'r�mf�'� .�.. S.L.lol.<�:7.:: 1 � -G . _ __. . Straw Bal¢s Staked �v�Eh 2 Sta'.es Per Gol� A1, � '. �,' r� f 0 0 ❑ u' u o — .. - ..�� -- . _ � � — _ � o i .... ,l � � o. - � IIIIIIIII Y_ � i� I i.- '__ � _ ��11 . 11 � I� � 'll I P ❑ '� . ._ ^� n ,- _ .'` I ,,', �1� PLAN VIEW Stn1<e Twine R�noff �-,'1�� f' ,(i', �w..� �� ;; ��— Gompacl;cd So�l Fil�,ered WaLer--� 5�G1"ION A-A AREA WLET FILTER 1z STRAW BALES � �x �H SEE SHT G-2 FOR GTY OF FORT COLfJNS � STANDARD AREA INLET DETAIL 1 � � _— ��; 'r��"t T�r_ r_�'a I��` �"� �JTG�K.'��l.C- LG'�C%4��Cit�.1 \,`,1 6 � �h�Tufa� L�;<-,�,T�C �al T'c \�� E DETCRM�NCD ) �� Goneral Notes: t. The maximum tributary aruo Is Ihnliod I to 0.25 acres per 100 faot ol lurir.u, � �' 2. Inspect and repair fonco nllnr uncli � storrr� event. Remova sodlrnuni wlion .� one half the ;.. ;,�'� of tho lonr,o lu�s becn fil ed. Removod sedimo��t slu;ll '� be deposited in a� aroa tributciry to ri v sediment basin or othoi filterinp measure SE¢¢Io�WoodPosl �'1-iIEerFabr�c E� Iz ,� �' r �� ' I i i �� ' ��II . ' F i,� I i I � i I II� il � �1 i � � I��i�� i . i i I �i� �. �� I I ii -� V � � � � � I �I,�i� , � ' �i I I' i�',II D � � I�lryl/ G � � , � � 1�� '� ��i�ll �_—BaCk�illu(� TY0nCI1 � _ � � �„�i�,�m�,��w;�;��'�' / 1 LINE � L\VJIVIV �.viv ii�v� � � // I PROTECT EXISTING FENCES � , AND UTILITY BbXES � ` �� _ �--- ` � � � l — Circle � �-� �_ � _" �rouse `_�- — _ �RY — — �_--- _ — � �� \ �i �� I— — . y — � �r _ —�- � � / / � _— �� SEeel o� - WOOC) POSF. E D A�Y I.andscape Architecture Ylr�nning l.%rban Uesign h;m�ironmental Analysis Site Engineering Graphic Design FDAW, Inc. 240 East Mountain Avenue Fort Collins, CO 80524 303 484-6073 _ FAX 303 484-8518 1380 Lawrence Street; Suite 300 Denveq CO R0204 303 534-0747 FAX 303 534-0844 �r�_�-n�ri ar l_: � ,i 1�-- C'it� of Fort Collins Coiorado t �� --SJ � � � Nu. Uate Revisions � July 10 1992 I�c � d for .onetn�etinn � S Q� � � — � — � Prujec[ No.c 1F589.01 Q� _Fillerinbrlc � ^ Ai�ach Securely �o Poal ��S1R"�� h�' ,TpM U J UraRed by: �M Compoclsd Backfill c,n��k�dn�: � R�norr All drawings and wntten marerial appearing herein � ' � II�II�� ronstitute original und unpubliehed w�ork uC I?UAW and may -� u Aprroxirna�ely �� n�m�,�,-� I�IIIII� -� 4 X�}` rf0ryGi1 �� ne duplicaced, useJ ur diqclnsed wi[hnut wntte[i consent. � ' SEGTIDN VIEW ONTRO� I SILT FENCE �NG INFO) - _ �'�E��MIn �� _ — - -- ' P� I �� '�� ___ S�P 4 9 19�2 � __� '_ _ --'�— �� . ,. l. �� ralnage � and � ��Sln� � � �4I1-��"� � Sheet No. F r_— 1 � : --c� �.- M I � � 1 � --- ,� a • 1 I � � � � EXIST. M TYP � � \ �� SECTION A-A (FROM SHT EC-1) � � � 1 � � i i \ \\ NOTE: ALL PARKING LOT SPOT ELEVATIONS ARE TOP BACK OF CURB UNLESS LABELED FL(FLOWLINE) � � � �� U ��`W E-� W x+ � � / `i.,\ �( �� u U � � I� I �\ FRENCH DRAIN PROFILE OFFSITE STREET FLOWS nwl=,` � � +0� 2-I-�� SD PROFI�E "A" � W r7 J � Z � W II � � EDAW, Inc. 240 East Mou�tain Avenue P'ort Collins, CO 80524 303 484-6073 FAX 3U3 484-8518 1380 Lawrence Street, Suite 300 Denver, CO 80204 303 534-0747 FAX 303 534-0844 Y � . D �A. •. • ' • � • • : • • 2::i5 LF 15" PVC � .5% Nu. Date Revieions July 10, 1992 Isa � .d for .ons niction 2+00 3+00 SD PROFILE "B" � � � F ,� t1LJ V. „,' .' .��o P�i.:.w 'L �°o�h"« �� F' �`-'�.� 1 � �� Lyri �1�s S ITE O'�S KG S fl�a< i r; :, �� h''J �SS �� e , �R1L, �P, NON- P&kFUrcA�tt�.J,7� q IZ��,�o �v�1�E _,�, 2 l -- Gr<�,ip�l f'lPF �,cirH . �/ � . �� .,, r�' j�IcOiE.� il�E w4_AFa SIMILaIZ. Q .� q" ��sE�Z �/ -�� '��N�,u�a�p g�( Aos,- - o n� T��r��,c�v �p (q"�,�-a ) E�` _ PE�-t'� v��.i:.;��i ,. � �V. �E2 �i:A'N 1 a c� �� • Ud� 4�� 4 �-� - j" - ��I<.A� �%lZ/i,thl Cl- At� ��.t�' (�.o.� 4��2ENCi�F P1ZA� i�l .� _. �Se�oE� -r'G�u�:�,� �... 1. u. �t'v� �. �n �� <Z�� .. i�M�µ. Z O F- U � � O Z N �C�z +wo omc� Z o �, h Z � 45 LF `V `� F= � 15" P VC � 1 � > �.78� � �, W z z �� Z `J -_ . v A � 0+00 1+00 2+00 SD PROFILE "C" GENERAL EROSION CONTROL NOTES 1. Keep disturbed azeas to a reasonable minimum at any one time. 2. Stabilize ali disturbed areas. 3. Keep �unoff to velocities not causing erosio�. 4. Retuin szdiment by filtering runoff end detain sediment-laden runoff for a period of time, allowing silt to settle out. 5. Provide diversion channels to direct cunoff around and away from dismrbed areas. 6. Kaep ail cut end fill slopes stabilized with terrscing or scarifying furrows perpendicular to the slope. 7. Protect alt drain inlets and culverts with sediment filters. S. Protect stcekpiled materials from wind erosion. Stockpiles are no[ to be higher t6an E' 9. Pemianent ground cover is to be established on atl disturbecl areas. Areas to be seede,�! which have beea compactzd by construction activities aze W ripped or likewise loosened priar to seecling. 10. Provide a temporary cover crop or an application of mulch to areas to retnain unseeclecl for greater than one month. Disturbed areas which have topsoil removed may tequire an applica[ion oF fertilizer prior to temporary seeding. Muich that is subject to windblow is to be disced inco the surface. 11. Inspect, clean and repair all erosion control roeasures the following work day after each storm event. 12. Additional erosion control wnstruction detai(s end specifications shall be taken from the City of Fort Collins Storm Drainage Design Cnteria and Construction StanJards. _ �- EG Vicinity Map � � �� N N r � jj 77 LF 15" PVC `jj Z � 0.0% z -��\ 60 . . . . .. _,<.....,. . . 5 � ��R��3L��t�,� �'»� � � 4+00 >> » � �° ��` �D�� PROFILE D �� EP 09 '19g2 c� � IiYllROLOGIC SUMMARY � IIISTORIC CONDII'IONS BASIN� SUBBASIN SUBACRES ACRES "c" A �j Ah 7.4 7.4 .20 B � Bh 14.6 22.0 .20 � DEVELOPED CONDITIONS BASIN ` Sn8;,r1SIN SUI3ACRPS ACRLS "c" A � ald 2.8 7..8 .35 U A2d 4.6 7.4 .35 A3d 7.9 15.3 .35 U A4d 4.1 19.4 35 B � Bd 2.6 22.0 .35 i� �� I.INDENMEIE�t� �� .. \. Landscape Architecture �/ Planning Urban Design Emironmental Analysis Site Cngi�eering N Graphic Design V.lo Scul� RUNOFF 1.6 cfs 3.6 cfs xurroFr 5.4 cfs 13.6 cfs 27.4 cfs 27.2 cfs 3.6 cfs Yroject No.: 1F568.1L Designed by: �� UraRed b}': �� Checked by: � All drnwings anJ wntten meterial appearing herein conatitute original and unp�6liehed work o[ EUAW and may not 6e duplioated, used or disclosed wi[houl written consent. 0 � • r � � • � � � � l-�'!�� Sheet No.