The URL can be used to link to this page

Home My WebLink AboutWATERFIELD P.U.D., 2ND FILING - FINAL - 7-95D - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTmM+t'M�S(T1 Y.Wss`►A q'e.. r.ucw.rJssw;ig.'8,1 — 011yµ«a > ri{"�•• Pats :. ADO OGO"' �` . !• .a .. -. �i... � W. AeM :1tr L"....iN y � � �•ti ' 1:} I :N .r• \ - FEEL, iddl ♦ . I 7 I i• I I ♦ 1 I ` I I I . 1 !,♦ II ♦ 1 - --- -�vlll 33 ow IW T ON T 7 N ♦♦� O I 4495 ............1.....a.. __ t I a rl i '�Oso ��bTEeFIE1D o- e!.! s`u .. ORI North I '� h Bilrck tt\\11LLHow -Yar I B UNG N r'_ IUnC n_ a e. '•. T}IERN TrD er Pa c �> ` � I WNTO �`! R°•I) `.>F ws ■' .� a FORT CO INS 4493 'I�s + 7;• ARPAR-------�9 inn .— ♦ ♦ � I a Is.n ■ � ' I 11 ♦. an t4 -- ,gill 35 ■ `I Trafi +, `a• railer\ ..r � <�ytl. '.._,. ^�` .a._ II �\�' Arro�• •t;l . :.Ny _T � . �1..-�1 '\�� '�'Ltipy YTK Q1. ``.. y^ r3•� ':7 .+1�.t?rM •`'• _ __• _�> I t�t• "91 go _! •r i a .• falsr: +[j3 ��'• ram• .�+:.�. _ s i Eaurs Park I . M CN Yc. f fPK ]' •LW W n Ypn<.1 w pm» rw.ep." oy ur( Ayy,° Nyr wa ttwrr unu[ timv.c .u.fdp l.W�r16 P•�.1M Qiyy Tel I 'Y�"n 1 -- C i WETLANDS AREA rwulpU.[Wnt<1 j 11.50 AC.i�- p • Pi � .24 I I (\l W1iT mz,=l lsA-4nb r••��r an Y t'..nR.<VRrO.I y�rr. µ.[PNM1 ' plll •4 In iHmlr A1D}• I � � • lnn wro. q t.R1<4irp• IT OnP ul01. iM MI (OYb Zf •Oppl i )tl •i <n I •ACO l' LLYY. Wl / u.VY1 pY N n°rtSlp.°pf,r DETAIL •n m, '. a,ror <w. eea < ••�i 0..•f°p. pf w em<s<ter.»l 14.4 1 1 ag�•�r rt .ppnp r W .IM M1Cm ln[ IIYi(N6 •R.1 n. nlad .awry V4 rW >Yr6 F,OrOr pT C NS ud r4 rW N^-=: SAMPLING POINTS 413, 8B do 17B A=E WITHIN THE WETLANDS AREA. W=—�=ND VEGETATION WAS REMOVED D'_'= 70 DISKING OF THE TOPSOIL 'N^—=AID DELINEATION PROv'C=D P_Y f•NMO<. r. O �urnd < Mi . - -.-IDE TECHNOLOGY, INC. i ryrNa.npf ,�y.t iW<Y tmmvTa� M. ..2 • �/ rtl pu�o J' x 1hv1 u(. As r )1r.i xja--- -- f' 1 4O.O� iAt E: \ DETAIL .�'a:f.•l to I ' Y, tot •f�.40n� rw,. \\ Q 1 .1...I 0Nn rYyj i!- COUNTY ROAD 48 (EAST VINE DRIVE) Ay auo r rd : ut r t�'a pl...+l s • Landstar Survevinee [nc. tw.p ymn aii•ro-r Propel No. 49185 �fml: LAND EXIHIBIT no tr:; car ci�mV Ei% NIGRI vT PTnvti<Ra pnn I l R VIgl!!TY MAP u s L.o l5T 1. 2. 3. 4. REFERENCES Storm Drainage Design Criteria and Construction Standards. City of Fort Collins, Colorado, May, 1984. Cooper Slough Master Drainage Study., by Simons, Li Drainage Criteria Manual. Urban Drainage and Flood Control District, Wright -McLaughlin Engineers, Denver, Colorado, March, 1969. Final Drainage and Erosion Control Study for Waterfield First Filing PUD. by Northern Engineering Services Inc, dated November 10, 1997 V. CONCLUSIONS Compliance with Standards All computations within this report have been completed in compliance with the City of Fort Collins Storm Drainage Design Criteria. Drainage Concert The proposed drainage concepts presented in this study and shown on the grading and drainage plans adequately provide for the conveyance and detention of developed runoff from the proposed development. If groundwater is encountered during construction, and dewatering is used to install utilities, a State of Colorado Construction Dewateing Wastewater Discharge Permit will be required. Stormwater Quality Because water quality is important to this developer, water quality mechanisms will be incorporated into all aspects of final design of drainage systems. The proposed water quality measures proposed in this study will require regular maintenance to remove deposits as they accumulate. Erosion Control Concepts The developer of this project understands that the wetlands adjacent to this project, must ` be protected during the construction process. Therefore, all erosion control measures, specified within these plans must be maintained and protected until all disturbed areas have been stabilized with vegetative methods. 1- I towards the existing wetlands. These ponds were sized using a 12 hour holding time per UDFCD standards. These water quality ponds can be vegetated with wetland type plants, and can be compatible with the surrounding habitat. Developed runoff will be directed towards ponds 301 and 321 by a combination of curb and gutters, and storm sewers. Street capacities will be checked to insure compliance with current City criteria. SWMM Model As mentioned above, a SWMM model was developed for the First Filing of Waterfield (a schematic of this model has been included in the appendix of this report). With the Second Filing, this model has been updated to show what is being proposed. (An updated schematic is also included). As you can see, basins 15, 16, and 18 of the First Filing model have been directed to Pond 321. Two models have been included in this study. The first represents conditions as they will exist with this development (ie The Senior Cottages parcel, and the School site are not developed). The second model includes these areas as being developed. The fully developed model will be used to size all outlet structures, and downstream conveyance elements. IV. EROSION CONTROL General Concept Waterfield PUD lies within the Moderate Rainfall Erodibility Zone, and the Moderate Wind Erodibility Zone, per the City of Fort Collins zone maps. At the time of final design, Per the City of Fort Collins Erosion Control Reference Manual for Construction Sites, the erosion control performance standard was calculated and copies included in the appendix of this report. In general, all disturbed areas not in a roadway section or a building pad area will be treated with a temporary seed and mulch, if not stabilized within 30 days of overlot grading, or sooner if any problems occur. In addition, straw bale check dams will be installed at 250' minimum intervals in all open channels, gravel filters will be installed and maintained on all curb inlets. Silt fence will be installed along the north, west, and east sides of the existing wetlands, as well as all along the westerly property line (adjacent to County Road 11) . Silt fence will be installed with the First Filing, around all disturbed areas in proximity to either the Plummer school outparcel, or the 5 acre outparcel on the south end of the project, and will be maintained until all disturbed areas have been revegetated. All construction activities must also comply with the State of Colorado permitting process for Stormwater Discharges associated with construction activities. A Colorado Department of Health NPDES discharge permit will be required before any construction grading can begin. Drainage Concepts When the Fast Filing was designed, all of the proposed developed stormwater runoff was directed to the southwest comer of the site, to pond 301. The pond was sized to accommodate all of the developed flows, and it was determined that approximately 13.5 ac.ft. of storage would be required. (Per the SWMM model, First Filing). A temporary interception channel was designed west of and adjacent to Merganser Drive directed the developed flows to Pond 301. This design concept was used in an effort to leave the wetlands area undisturbed. The design of the Second Filing incorporates the existing wetlands area for some of the developed runoff, as well as for site detention. SWMM basins 15, 16, and 18 , which were directed with the Fast Filing to pond 301, have been redirected as a part of this study to the wetlands area (designated as Pond 321 in the SWMM model). Also SWMM basins 21 and 22 have also been directed to the wetlands area. Developed Basins 10, 12, 13, 14, 17, 23, and 24 will continue to be directed towards pond 301, located in the southwesterly comer of the site. Pond 301, as designed with the First Filing had a temporary outlet structure and emergency overflow weir designed. These structures were sized for only the first filing. With the design of the Second Filing, these temporary structures associated with that pond can be finalized. With the First Filing, no water quality volume was included in Pond 301, with the second Filing, approximately 1.2 acre.feet of additional volume has been included. Per the SWMM model, approximately 10.4 acre.feet of storage volume will be required. This will reduce the 100 year WSEL in Pond 301 from 38.95 to approximately 38.5. This does provide the necessary 1 foot of freeboard required by City policy. This also gives a maximum release rate from the pond of 5.8 cfs. With the Second Filing, the existing wetlands area will be utilized for some site detention. This existing wetlands has been observed to have a high water line of approximately 4950.00. From the existing topography of the area, it appears that this wetlands area would overtop its banks at approximate elevation 4952.00. Flows overtopping the existing wetlands appear by the existing topography to be directed to the existing Lake Canal. This same concept is being proposed with the Second Filing. It is our intent to maintain a permanent water surface elevation of approximately 4950.00. This would be accomplished by setting the top of an outlet control box at the 4950.00 elevation. The developed SWMM model shows that approximately 12.9 acre.feet of detention storage would be required to be provided. This can be accomplished at approximate elevation of 4951.62, based on the existing topography. It is our intent to leave this area and the existing grades undisturbed. As mentioned above, the existing wetlands would appear to overtop somewhere in the vicinity of elevation 4952.00. An emergency overflow weir is not being proposed with this development as it is our intent to leave this area as undisturbed as possible. In an effort to keep the wetlands as natural as possible, two small water quality ponds are being proposed at the outlets from Poochard Drive and Mute Swan Court. The intent of these ponds is to allow the first flush from storm events to drain to these ponds, and sheet flow over the top I To calculate the historic flows, used to determine the allowable historic release from the site to Lake Canal, per City criteria, only Basin H4 is considered historic to Lake Canal. Developed flows located in historic basin H-5 will be detained and released into Lake Canal. A small undeveloped portion of the northeast comer of the site (part of the First Filing) will also release into the Larimer and Weld Canal. As mentioned above there is an existing wetland located on this site. A report entitled "Jurisdictional Wetlands Delineation Survey for the Country Club Farms LLC, Larimer County, Colorado" by Riverside Technology was prepared for this wetland, and submitted to the City with the Preliminary PUD submittal under separate cover. A copy of the wetland delineation map has been included in the appendix of this report. Included as a part of this submittal is a study from Riverside Technology, who has developed a groundwater hydrological model of this site. III. DEVELOPED DRAINAGE ® Design Criteria and References Drainage criteria outlined in both the City of Fort Collins Storm Drainage Design Criteria Manual. and Storm Drainage Criteria Manual by the Urban Drainage and Flood Control District have been used for this Final Drainage Study. The groundwater hydrological model, developed by Riverside Technology, will also be used for all flows directed towards the wetland area. Hydrologic Criteria The Rational Method was used to estimate peak stoimwater runoff from the proposed site. The 2 year storm event and the 100 year storm event were used to evaluate the proposed drainage system. Rainfall intensity data for the Rational method was taken from the City of Fort Collins Stormwater Utility Intensity curves (Figure 3-1). A SWMM model was developed for the first filing representing the interim concepts associated with the First Filing. This model was updated for the Second Filing as a part of this study for the remainder of the site. A SWMM model was done for the anticipated effects of the Second Filing, and another model was completed which assumes the Senior Cottages of America Tract, and the School site fully developed. Hydraulic Criteria City of Fort Collins Storm Drainage Criteria has been used for all hydraulic calculations. 11 Final Drainage Report for r Waterfield PUD, Second Filing I. GENERAL LOCATION AND SITE DESCRIPTION The Waterfield PUD development is located at the northwest comer of East Vine Drive (County Road 48) and Summit View (County Road 9E). The site is also bounded on the north by the Larimer and Weld County Canal. The existing Plummer School is located to the southeast of this site. The site can also be described as a portion of the southwest quarter of Section 5, Township 7 North, Range 68 West of the 6th PM, City of Fort Collins, Larimer County, Colorado. A vicinity map of the site is included in the appendix of this report. This site is also located within the Cooper Slough Major Drainage Basin. The Waterfield PUD includes approximately 140 acres. The site is presently undeveloped, has most recently been used for agricultural purposes. The site generally slopes from the west to the east at slopes between 1 % and 5%. There is an existing wetland located adjacent to this site, which occupies approximately 11.50 acres. The First Filing of Waterfield includes the Bull Run Apartment project, located in the southeast comer of the site, as well as approximately 42 single family lots located in the northeast comer of the site. The Second Filing of Waterfield contains the remainder of the single-family lots, the Day Care, and the Convenience Store site. The tract, designated as the Park site and the future school site have been platted with this project, and have been designated as Tracts. The site designated as the Senior Cottages of America was platted with the Fast Filing, as a Tract. H. HISTORIC DRAINAGE Historically, the vast majority of the site drains to the existing Lake Canal, located at the southwest comer of the site. A copy of the existing site, with the historic drainage basins has been included in the appendix of this report. Basins H-1 and H-2 drain south to existing irrigation laterals and on south to the existing wetlands area. Basin H-3 drains directly to the existing wetland area. This existing wetlands appears to overtop at approximately elevation 4952, and flows south to Lake Canal. This assumption is based on the existing topography which clearly delineates historic drainage in this direction. Basin H-4 drains directly to Lake Canal. Basin H-5, located at the southeast comer of the site, drains to an existing low point located around the old Plummer School. Drainage from this basin would eventually overtop Summit View, and drain to the east. Basin H-6, located in the extreme northeast comer of the site, drains to the existing Larimer and Weld Canal. Virtually no offsite drainage enters the site. INovember 17, 1997 I i I I A I I it Mr. Glen Schleuter City of Fort Collins Stormwater Utility 235 Mathews Fort Collins, Colorado 80522 RE: Waterfield PUD, Second Filing Fort Collins, Colorado Project Number: 9768.00 Dear Glen: N O R T H E R N E N G I N E E R I N G SERVICES INC Northern Engineering is pleased to submit this Final Drainage Report for the Waterfield P.U.D, Second Filing. for your review. It represents a study of existing and proposed stormwater characteristics of the project site. This report was prepared in compliance with technical criteria set forth in the, City of Fort Collins, Storm Drainage Design Criteria and Construction Standards manual. If you should have any questions or comments as you review this report, please feel free to contact me at your convenience. Sincerely, NORTHERN ENGINEERING SERVICES, Roger A. Curtiss, P.E. Jim McCory - Colorado Land Source Is, 27332 420 SOUTH HOWES, SUITE 202, FORT COLLINS, COLORADO 80521, (970) 221-4158, FAX (970) 221-4159 Final Drainage Report for Waterfield PUD, Second Filing Fort Collins, Colorado November 17, 1997 Prepared For: Colorado Land Source 8101 East Prentice Avenue, Suite M180 Englewood, Colorado 80111 Prepared By: Northern Engineering Services, Inc. 420 South Howes, Suite 202 Fort Collins, Colorado 80521 (970)221-4158 Fax(970)221-4159 Project Number: 9768.00 Initial Submittal I Final Drainage Report for Waterfield PUD, Second Filing Fort Collins, Colorado November 17, 1997 SERVICES INC