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Home My WebLink About1.0 ApplicationENARTECH lnc. Consulting Engineers and Hydrologists GARFIELD COUIITY February 11,1997 Mr. Mark Bean Garfield County 109 Eighth Street, Suite 303 Glenwood Springs, CO 81601 RE: Mitchell Creek Floodplain Zote District Map Amendment Dear Mark: -\ylzz- -ZAIS- ^ZIN. This letter is to request a Zone District Map Amendment of the Mitchell Creek Floodplain on behalf of Storm King l-ands. Enclosed is a map illustrating the areas to be removed from floodplain designation. Also enclosed is a list of property owners within the floodplain and adjacent property owners. The proposed floodplain map amendment affects properties located in Garfield County and within the City of Glenwood Springs; Storm King Lands owns the Glenwood Auto Plaza property which is located within the city limits" The purpose of this request for a Zone District Map Amendment is to provide public notice as required by the Federal Emergency Management Agency (FEMA) and by the National Flood Insurance Program Regulations. The requested floodplain map revisions are to correct an error in the original Flood Insurance Study that was prepared for Garfield County and FEMA" dated January 3, 1986. The Flood Insurance Study shows overbank flow in Mitchell Creek occurring north of Donegan Road and across Donegan Road, resulting in widespread flooding outside of the channel of Mitchell Creek. Analysis by Enartech, Inc., including field survey of cross-sections across Mitchell Creek and computer analysis using the }IF;C-} floodplain model, concluded that on the reach of Mitchell Creek north of Donegan Road, the 100-year flood waters are contained entirely within the channel of Mitchell Creek and within the existing bridge across Donegan Road. The error in the original Flood Insurance Study was caused by incorrect elevation data that was obtained from a Z-foot contour topographic map. This topographic map is not sufficiently detailed or accurate for a floodplain analysis on a small stream such as Mitchell Creek. Mitchell Creek is also densely vegetated, which reduces the accuracy of topographic mapping based upon aerial photography. The analysis performed by Enartech was based upon field surveyed cross-sections across Mitchell Creek immediately north of Donegan Road (Cross-sections H, I, J and K 302 Eighth Strcet, Suite 325 P.O. Drawer 160 Glenwood Sprlngs, Colorado 81602 (303) 945-2236 FEB 11 199't Mr. Mark Bean Page - 2 on the Flood Insurance Maps). The technical details of Enartech's floodplain analysis are outlined in my August 17, 1988 letter to Kevin Kadlec; a copy of which was forwarded to your office. Please forward this request for a Zone District Map Amendment to the Board of County Commissioners for referral to the Planning andZoning Commission and for scheduling a public hearing before the Board. As we have discussed, I would like to schedule this item for review by the Planning and Zoning Commission during their March 13th meeting, and the Board of County Commissioners during their April 1st meeting. If you have any questions or require additional information, please give me a call. Thank you for your consideration of this matter. Sincerely, ENARTECH, INC. Peter Belau, P.E. PB/des Y22642 (Beanl) Mr. Willis Parkison Mr. Brian Hyde Ms. Irslie Klusmire \la/ LEGEND CITY LIMITS AREAS TO REMAIN DESIGNATED AS FLOODPI.AIN AREAS TO BE REMOVED FROM FLOODPI.AIN DESIGNATION MITCHELL CREEK FLOODPI.AIN PROPOSED MAP REVISION FEBRUARY, 1991 v -ath- ^ZIt\\ ENARTECH lnc. CONSULZNG ENG'NEEFS AND HYDFOLOGISTS P.O. ORAWER 160 6LENWOOO SPR/NGS, COLORADO 81602 (303) 915-2236 ,NTERSTATE 70 K,$ - ffi \,"/ ./ t/il SCALE:1'= 200' CITY OF GLENWOOD SPRINGS GARFIELD COUNTY IIMITCHELLCREEK FLOODPIAIN - PROPOSEb MAP REYISION PUBLIC NOfiCE MAILING LIST FOR PROPERTIES IN GARFIELD COI.iNTT Beightel, Gregory & Tercsa Ingelhar( Fred & Judy Moda, Mary fi)67 Sun King Drive ?i07 - 1S4 Road 0192 - 130 Road Glenwood springs, co 81601 Ghnwood springs, co E150r Ghnwood Springs, co g1601 Bentder, Harold, Jr. & tori Kindall, Harold & Stefani Bowles, Bruce & Mary fi)44 Donegan 0174 - 130 Road 068E - l:t2 Road Glenwood springs, co 81601 Glenwood springs, co 81601 Glenwood springs, co g1601 Kieclq Kenneth & sharron Bowles, Allan & Joyce Hakanson, Donald & susan P.O. Box 33 p.O. Box 1137 0136 - 130 Road Glenwood Springs, co 81602 Glenwood springs, co E1602 Glenwood springs, co t1601 Yellico, Eugene & susan Mortenson, Daniel & stacy Ross, Richard & Judith (X)11 Ponderosa 011g - Road titO fi)23 ponderosa Drive Glenwood springs, co 81601 Glenwood Springs, co 81601 Glenwood springs, co g1601 Metzler, Robert Centner, Thomas & Marilyn NewYork Guardian Mortgagee Corp. P.O. Box 1198 923 palmer p.O. Box g70 Idaho springs, co 80452 Glenwood springs, co g160r Hempstead, Ny 11550 Phillips, James & SUtt, Cheryl HuB James & Theresa Maher,Ihomas & Brenda 0237 Donegan Road 01ffi - tjiO Road 0231- lj]0 Road Glenwood springs, co 81601 Glenwood Springs, co 81601 Glenwood springs, co g1601 Vidakovich, John & Beatrice Wiencek, Kenneth & JilI Toth, Julius, Jr. P'o' Box 1072 0123 creekside court 2610 w. Ftorida Ave. Glenwood Springs, co E1602 Glenwood springs, co t1601 l)enver, co g021g McClenahan, John & sandra conwaS James & Dakin, Ann Fockler, David & shirley 1103 Valley View Road 0147 - 130 Road p.O. Box 24&3 Glenwood Springs, co t1601 Glenwood Springs, co 81601 Glenwood Springs, co g1602 Sorensen, Frcderick & Mary Johnson, Keith & Judith Rovig Myles & lVinnifred 0141 - 130 Road 0353 Mountain Shadows Dr. 0125 - 130 Road Glenwood Springs, co 81601 Glenwood springs, co 81601 Glenwood springs, co g1601 -*,#'I3II"?,;H,l[d??,"iiH*"-#J#3?"H"]f#r8il,** MelbS lGnneth Urban, Patricia & George Rippy, Grcg & Marilee c/o KLM Constnrction ffi39 Crcekside Court 02(l Creekside Court P'O. Box 484 Glenwood Spring's, CO t1601 Glenwood Springn, CO t1601 Glenwood Springs, CO t1602 Hughes, Douglas Mitchetl Creek Homeownerrs Assoc. Tarrrlay & Susan P.O' Box 163 c/o Kenneth Wiencck (XDS Creekside Court Nar Casfle, CO 81647 OUB Creetrside Court Glenwood Springs, CO E1601 Glenwood Springs, CO 81601 Straus, Mark & Susie 824 MintcrAvenue Glenwood Springs, CO t1601 2 MITCIIELL CREEK F'LOODPIAIN - PROPOSED MAP REYISION PT]BLIC NOTICE IVIAILING LIST FOR PROPERTIES IN CITY OF GLEI{WOOD SPRINGS Storm King Lands c/o Mr. Willis Parkison 2311 Meadowlark Lane Glenwood Springs, CO E1601. Ken Kriz M97 County Road 167 Glenwood Springs, CO t1601 J GARFIELD COUNTY REGULATORY OFFICES AND PERSONNEL September 26,1991 Ms. Roya Rashidmanah Michael Baker Jr., Inc. 1420 King Street, 4th Floor Alexandria, VA 22314 RE: Mitchell Creek CLMOR Glenwood Springs, CO Dear Ms. Rashidmanafi: please consider this letter to be confirmation of my concurrence with the statements made by Peter Belau, P.E., ENARTECH Inc., in his September 25,1991 letter. The notice referenced the floodplain, which does include the floodway of Mitchell Creek. If you need any further statements, feel free to call or write to this ofltce, at your convenience. Sincerely, Mark L. Bean, Director Regulatory Offices and Personnel MLB/rlb xc: Peter Belau, ENARTECH, Inc. Leslie Klusmire, City of Glenwood Springs 109 8TH STREET, SUtrE 303 . g45-82t21625-557t1285-7972 . GLENWOOD SPRINGS, COLORADO 81601 ENARTECH lnc. Consulting Engineers and Hydrologists September 25,1991 Ms. Roya nasnttnandi Michael Baker Jr., Inc. 1420 King Street, 4th Floor Alexandria, VA 223L4 RE: Mitchell Creek CI-OMR Glenwood Springs, CO Dear Ms. Rashivmanasi: -\svzz- -ZlllS- ^ZIN. This letter is to certiff that the City of Glenwood Springs and Garfield County have provided public notice to all affected property owners stating the intent to revise the flood plain, including the floodway, of Mitchell Creek. Both the City and the County held public hearings in this regard, and public notices were mailed to all affected property owners via certified mail. Sincerely, ENARTECH,INC. .---/ .- )t*-\-rl=.\),-,,-(-^- Peter Belau, P.E. PBldes cc: Mark Bean, Garfield County kslie Klusmire, City of Glenwood Springs Willis Parkison n2a2Q26_02_A) f-,l}l"$tffi irfA*S 302 Eighth Strcet, Suite 325 P.O. Drawer 160 Glenwood Sprlngs, Colorado 81602 (303) 945-2236 ENARTECH lnc. Consulting Engineers and Hydrologists February ll,799l Ms. kslie Klusmire City of Glenwood Springs 806 Cooper Glenwood Springs, CO 81601 RE: Mitchell Creek Floodplain Map Amendment Dear Irslie: -\svzz- -Zl\N- ^61N. This letter is to request a public hearing to consider a Map Amendment of the Mitchell Creek Floodplain on behalf of Storm King I-ands. Enclosed is a map illustrating the areas to be removed from floodplain designation. Also enclosed is a list of property owners within the floodplain and, in Garfield County, adjacent property owners. The proposed floodplain map amendment affects properties located in Garfield County and within the City of Glenwood Springs; Storm King I-ands owns the Glenwood Auto Plaza property which is located within the city limits. The purpose of this request for a public hearing is to provide public notice as required by the Federal Emergency Management Agency (FEMA) aod by the National Flood Insurance Program Regulations. The requested floodplain map revisions are to correct an error in the original Flood Insurance Study that was prepared for Garfield County and FEMd dated January 3, 1986. The Flood Insurance Study shows overbank flow in Mitchell Creek occurring north of Donegan Road and across Donegan Road, resulting in widespread flooding outside of the channel of Mitchell Creek. Anatysis by Enartech, Inc., including field survey of cross-sections across Mitchell Creek and computer analysis using the LfrC2 floodplain model, concluded that on the reach of Mitchell Creek north of Donegan Road, the l0Gyear flood waters are contained entirely within the channel of Mitchell creek and within the existing bridge across Donegan Road. The error in the original Flood Insurance Study was caused by incorrect elevation data that was obtained from a Z-f.oot contour topographic map. This topographic map is not sufficiently detailed or accurate for a floodplain analysis on a small stream such as Mitchell Creek. Mitchell Creek is also densely vegetated, which reduces the accuracy of topographic mapping based upon aerial photography. The analysis performed by Enartech was based upon field surveyed cross-sections across FEB 11 1991 GAnIELU "rrfVfF 302 Eighth Street, Suite 325 P.O. Drawer 160 Glenwood Sprlngs, Colorado 81602 (303) 945-2206 Ms. Irslie Kl Page - 2 Mitchell Creek immediately north of Donegan Road (Cross-sections H, I, J and K on the Flood Insurance Maps). The technical details of Enartech's floodplain analysis are outlined in my August 17, 1988 letter to Kevin Kadlec. Please forward the enclosed information to the Planning and Zorung Commission for a public hearing during the February 2Tthmeeting. If you have any questions or require additional information, please give me a call. Thank you for your consideration of this matter. Sincerely, ENARTECH, INC. t usmire Peter Belau, P.E. PB/des ruffi2 glusml) Enclosures cc: Mr. Willis Parkison Mr. Brian Hyde Mr. Mark Bean yi GARFIELD LEGEND CITY LIMITS AREAS TO REMAIN DESIGNATED AS FLOODPTAIN AREAS TO BE REMOVED FROM FLOODPLAIN DESIGNATION MITCHELL CREEK FLOODPI.AIN PROPOSED MAP REVISION FEBRUARY,1991 CITY OF GLENWOOD SPRINGS INTERSTATE 70 ENARTECH lnc. GIE ....v .ZLE. ^ZIN. TTMITCHELL CREEK FLoODPLAIN - PRoPosED MAP REYISIoN rLiDLlt- r\LrllL.f- lVlAILll\\, rrlDr IUl(fK(rf!-KlltS fN GAK.tilfrLD COUN'f'Y Beightel, Gregory & Teresa Ingelhar! Fred & Judy Moda, Mary fi)67 Sun King Drive 2307 - 154 Road Dtgl- -130 Road Glenwood springs, co t1601 Glenwood springs, co 81501 Glenwood springs, co t160r Bentzler, Harold, Jn & Lori Kindall, Harold & Stefani Bowles, Bruce & Mary 0044 Donegan 0174 - 130 Road 06gt - 132 Road Glenwood Springs, CO 81601 Glenwood Springs, CO g1601 Glenwood Springs, CO gf60l Kieck, Kenneth & shamon Bowles, Allan & Joycr Hakanson, Donald & susan P.O. Box 33 p.O. Box 1137 0ljt6 - 130 Road Glenwood springs, co 81602 Glenwood springs, co t1602 Glenwood springs, co t1601 Yellico, Eugene & susan Mortenson, Daniel & stacy Ross, Richard & Judith (X)11 Ponderosa 011g - Road 130 fi)23 ponderosa Drive Glenwood springs, co 81601 Glenwood springs, co t1501 Glenwood springs, co g1601 Metzler, Robert Centner, Thomas & Marilyn NewYork Guardian Mortgagee Corp. P.O. Box 119t 923 palmer p.O. Box gZ0 Idaho springs, co tM52 Glenwood springs, co 81601 Hempstead, Ny 11550 Phillips, James & Stitt, Cheryl Hulf, James & Thenesa Maher, Ihomas & B*nda 0237 Donegan Road 01(X) - iltO Road O23t - liiO Road Glenwood Springs, co t1601 Glenwood springs, co 81601 Glenwood springs, co g1601 Vidakovich, John & Beatrice Wiencel, Kenneth & Jill Toth, Julius, Jr. P'o' Box 1072 0123 creerside court 2610 w. Ftorida Ave. Glenwoodsprings,co E1602 Grenwoodsprings,co t160r Denver,co g02r9 McClenahan, John & sandra connaS James & Dakin, Ann Fockler, David & shirley 1103 Valley View Road 0147 - 130 Road p.O. Box 24&3 Glenwood Springs, co E1601 Glenwood Springs, co 81601 Glenwood springs, co g1602 sottnsen, Frederick & Mary Johnson, Keith & Judith Rovig Myles & winnifred 0141 '130 Road (L353 Mountain Shadows Dr. 0t25 - il]o Road Glenwood springs, co 81601 Glenwood springs, co 81601 Glenwood springs, co g1601 -. .j..^ MITCHELL CREEK F'LOODPIAIN. PROPOSED MAP REVISION PI.]BLIC NOTICE MAILING LIST FOR PROPERTIES IN GARFIELD COLINTT MelbS Kenneth c/o KLM Constmction P.O. Box 484 Glenwood Springn, CO 81602 Hughes, Douglas P.O. Box l6i New Castle, CO t1647 Straus, Mark & Susie 824 Minter Avenue Glenwood Springs, CO t1601 Urban, Patricia & George ffi39 Creekside Court Glenwood Springs, CO t1601 Mitchell Creek Homeowney's Assoc. c/o Kenneth Wiencek 0123 Creekside Court Glenwood Springs, CO 81601 Rippy, Grcg & Marilee 0213 Creekside Court Glenwood Spri"gn, CO 81601 T.arrrlay & Susan fiD5 Crcekside Court Glenwood Springs, CO t1601 2 3 January 15, T,.TENARTECH lnc' Consulting Engineers "o "o'"''n'TJ Mr. MarkBean -\SYZ7- Garfield County Planning Director -ZA!\\r-L?#::ts;:ffi,'3f3?;,, ^zlN. RE: Mitchell Creek Floodplain Dear h{ark, Enclosed is a copy of the "public notice" request that I received from FEMA regarding my request to revise the floodplain map for Mitchell Creek. Also enclosed is a copy of FEMA's regulations regarding public notice. The effected reach of Mitchell Creek is from Donegan Road north about 400 feet along Mitchell Creek (to Section K-K on the Floodplain Maps). Please let me know how the County would like to proceed with this public notice. The Commissioners have previously reviewed this matter (February 7, 1990letter from Marian Smith); I do not know if a public hearing was held at that time. Sincerely, PB/des P2:2,641, (kan) Enclosures ENARTECH, INC. r Belau, P.E. 302 Eighth Street, Suite 325 P.O JAN 16 1991 GAiTFIELD COUNTY nil U Description of Data L2. Documentat,ion, as shown below, concerning the approval of Ehe revised floodway (See Sections 65.7(b)(1) , (Z), and (3) of rhe NFrP regulations. ) x Copy of the public notice distributed by Ehe community stating Ehe community I s intenE Eo revi se Ehe floodway or a sEaEement by Ehe community that it has noEified all affected property oerners and affected adjacent jurisdictions Copy of a letter appropriaEe Stat.e floodway revision DocumentaEion of the revi sed f 1-oodway by State agency notifying agency o f Required Received x x x Ehe the approvaL of Ehe the appropriate 13.Corporate limit map and/or annexation ordinances EhaE reflect the current communiEy boundaries L4. A topographic map that shows the revised 100- and 500-year floodplain and floodway boundaries, Ehe locat,ions and alignmenEs of all cross sections used in the revised hydraulic models (Items 9 and 11), sEream alignment,s, road alignment,s, and t,he community boundaries. The revised floodplain and floodway boundaries must tie into Ehose shown on the effective FIRM/FIRM and FBFM upstream and downst,ream of the revised reach. The scaie anri topographic definition of the map must be sufficient t.o provide reasonable accuracy, and the map musE be cerEified by a regisEered professional engineer.(see SecEion 65.6(a)(ff) and 65.7(b)(5) of Ehe NFIP regulat,ions. ) 15. ttAs-builtI pIans, cerEi professional engineer elemenEs, specifically fied by a , for all regi s Eered project Y Federol Emergency M3eemenl Agency (L) Ch ong es qllec ting-tty d,rolo gic c on-ditiotts. The following data must be submitted(i) General description of the changes (e.9., darn, diversion channel, or detentlon basin).'(ii) Constnrction plans for as-built conditions, lf applicable.(iii) New hydrolosic analysis ac-counting for the effects of the changes.(iv) New hydraulic anaiysis and pro- files using the new flood discharge values reslr]li.a fror, tirc h:'*ologic analysis. (v) Flevised dellneatioru of the floodplain boundaries a.nd floodway. (2) Chonges alfecting hyd,roulic con- d,itiotts. Ttre following data shall be submitted:(i) Genc.-*l description of the changes (e.9., channslization or new bridge, culvert, or levee).(ii) Construction plans for as-built conditions.(iU) New hydraulic uralysis and flood elevation profiles accounting forthe effects of the changes and usingthe original. jLood clischarge values upon which the original map is based.(iv) Revised delineations of the floodplain boundaries and floodway.(3) Chonges intsohing topographic conditiotts. The following data shall be subnlitted:(i) Geaeral description of the changes (e.9., grading or fillrngl.(ii) New topographic lnformation, such as spot elevatlons, cross sectionsgrading plans, or contour Eaps.(iii) Revised delineations of the floodplain boundaries and, tf necessary, Iloodway. (d). Data requiremenb lor incol7to-roti.ig improoed, dcta. Requests forle- visions based on the use of improvedbydrologic, hydraulic, or topographic data shall include the fo[owing daia:(1) Data that are believed to bebetter than those used in the originalanalysis (such as additional years ofstree'n gage data).(2) Docr:oentation of the source ofthe data. (3) Explanatiou as to why the use ofthe new data will irnprove the resultsof the oricinal analysis.(4) Revised hydrologic analysiswhere hydrologic data are being inior-porated. _ (5)_ Revised hydraulic analysis andflood elevation profiles where new hy-droiogic or hydraulic data are beinsincorporated. (6) Revised delineat'ions of the floodplai:e bouadaries and floodway where $ 6s.7 new hydrolog:ic, hydraulic, or topo-graphlc data are being incorporated. G) Dato requiremenb for incot?o-roting improoed, m"ethods. tlequestsfor revisions based on the use of im-proved hydrologic or hydraulic meth- odology shall tnclude the following data: (1) New hydrologic analysis when analternative hydrologic methodolocy is . being proposed. (2) New hydraulic analysis and floodelevation proflles when an alternativehyrologic or hydraulic methodoloely isbeing proposed. (3) Expla.nation as to why the alter-native methodologies are superior tothe original methodologies. (4) Revised delineatioru of the floodplaia bouadaries and floodway based on the new analysis(es).(f) Certficotiott requirernznts. A]tanalysis and data submitted by the re-quester shall be cerfifled by a regis-tered professional engineer or licensed la.nd surrreyor, as appropriate, subjectto the definltion of ..cerilflcaflon,' given at ! 65.2 of thts subchapter.(g) .Subzissioz proueoures. All re-quests shall be submitted to the appro-priate FU\ltA Regional Office servleing the commtrnity's geographic area t51 fB, 3031{, Aug. 25, 1986, as aneuded at 53 lR, 16279, May 6, 19881 g 65.7- Floodway revisions. . G) @neral Floodway data ls devel.oped as part of FE[ttA Flood Insur- ance Studles and 15 uftltzgd by commu- nlties to select and adopt floodways aspart of the flood piain management progra.trr required by ! 60.3 of thls sub-chapter. When it has been determlned by a community that no practicable al- teraatlves exlst to revising the bound- aries of its previously adopte<i flood- way, the procedures below shall be fol- lowed-(b) Dato requirenntts uhztt bcse tlood, elcoation chonges are requcsted- When a floodway rerr-Lsion is requestedin association with a change to baseflood elevatlons, the data requlre- menls of $ 65.6 shall also be applica-ble. In additiorU the following docu- mentatlon shall be submitte&(1) Copy of a public notice distribut- ed by the comnr:nity stattng the com-munity's lntent to rerrise the floodwayor 9. statement by the comro.unity thatit has notified all affected property ownersi and. affected adjacent Jurisaic-tions. (2) Copy of a letter notifying the ap_propriate State agency of the flood-way revision when the State has juris- 355 Federal Emergency Management Agency Washington, D.C. 20472 Rf, CERTIFIED MAIL TURN RECEIPT REQUESTED The Honorable Ted O'Leary Mayor, City of Glenwood Springs 806 Cooper Avenue Glenwood Springs, Colorado' 81601 IN REPLY REFER TO: I02 Community: UnincorporaEed &AeF. of Garfield County, Colorado Map Panel Numberss FIRI'{ 080205 1043 B, 1431 B FBFM 080205 1043, 143 I EffecEive Date of This Revision:NOV 15 I99I Dear Mayor OrLeary: This is in response to a letter dated October 28, 1991, from Mr. PeE,er Belau, P.8., ENARTECH, Inc., regarding Ehe effective Flood Insurance SEudy (FIS) report,, Flood Insurance Rate Map (FIRM), and Flood Boundary and Floodway Map (f'SfM) for the unincorporaEed areas of Garfield County. Mr. Belau submitted additional information Eo support his initial requesE dated March L4r 1991, for a Let,ter of Map Revision (LOMR) for a reach of Mitchell Creek from jusE upsEream of Interstat.e Highway 70 Eo approximaEely 1r050 feet, upstream of Donegan Road in the vicinicy of the Glenwood Aut,o PLaza Subdivision. A porEion of the revised reach has been annexed by Ehe City of Glenwood Springs, Colorado, but is currently shown on Ehe effective FIRM and FBFM for the unincorporated areas of Garfield County. Mr. Belau requested thaE we revise Ehe effecEive FIS reporE, FfRM, and FBFM Eo show Ehe effecEs of beEEer topographic surveyed daEa along Mitchell Creek aE FIS Cross SecEions H, I, J, and K, and t,he consEruction of a bridge aE CenEer Drive Road wichin Ehe Gtenwood Aut,o Plaza Subdivision. All of the daEa required to evaluaEe this request for a LOMR $rere submict,ed with let,ters daEed beEween March 14 and OcEober 28, I99I, from Mr. Belau. We have completed our review of Ehe submitted daEa with regard to the daEa used t,o produce Ehe ef f ect ive FIR]'{ and FBFM, and have revi sed t,he FIRI'{ and FBFM t,o modify Ehe elevations and floodplain and floodway boundary delineations of a flood having a l-percenE probability of being equaled or exceeded in any given year (base flood) along Mitchell Creek for the revised reach. The revised hydraulic model which utilized addicional topographic surveyed daEa shows that the 1O0-year flow is conEained within Ehe nat.ural channel at Ehe above-ment.ioned cross sect,ions. The base (100-year) flood elevations (gpns) decrease E.hroughout, the revised reach excepE in one area upsEream of Donegan Road at Cross Sect,ion I, and E,he 500-year flood is no longer contained within t.he culvert aE Donegan Road, The modificaEions are shown on E,he enclosed annoEaE.ed copies of FIRM Panels 1043 B and 1431 B and FBFM Panels 1043 and 1431, Profile Panels 74P, 75P, and 76P, and the Floodway Data Table. This LOMR hereby revises Ehese panels of the effect ive FIRM and FBFM, both dated January 3, 1986, for the unincorporaEed areas of Garfield County, Colorado. 2 The following table is a partial listing of former and modified 100-year flood elevaEions. Exist,ing Base rJcarion tt"3,trll:vation Modified Base Flood Elevat,ion ,'.( f eet ) Approximately 530 feeE upsE,ream of IntersEaEe Highway 70 Just, upstream of Donegan Road Approximately 115 feet upsEream of Donegan Road ApproximateLy 165 feet upst,ream of Donegan Road Approximately 450 feet upstream of Donegan Road 'kNational Geodetic Vert,ical Datum,rounded to Ehe nearest. whole foot,. .:r5 r725 x5 ,7 63 -:r5 ,7 69 -:r5 ,77 L x5 r79L .:r5 rl24 -:r5 r762 -:r5 r766 *5 r774 -:r5 r7g7 Because of currenE funding consE,rainEs, ere musE limit Ehe number of physical map revisions. Consequentty, we will not, publish a revised FIRM and FBFM for Ehe CiEy of Glenwood Springs t,o reflect Ehese modifications at this t,ime. However, if in Ehe fuEure, we revise and republish the FIR}'! and FBFM panels affected by this LOMR, $re will incorporate Ehe previousty described modifications aE EhaE Eime. The floodway is provided to your community as a Eool Eo regulaEe floodplain developmenE. Therefore, Ehe floodway modificaEions described in this leEEer, while acceptable Eo Ehe Federat Emergency ManagemenE Agency (f'nUa), must also be accepEable Eo your communit.y and adopted by appropriaEe community acE,ion, as specified in Paragraph 60.3(d) of Ehe NaEional Flood Insurance Program (NFIP) regulations. These modifications have been made pursuant to Section 206 of E,he Flood Disaster Protect,ion Act, of 1973 (P.L. 93-234) and are in accordance with the National Flood Insurance AcE of 1968, as amended (Title XIII of the Housing and Urban Development, Act of 1968, P.L.90-448),42 U.S.C.4001-4128, and 44 CFR, ParE 55. Public notification of modifications Eo Ehe BFEs along Mitchell Creek will be given in Ehe Glenwood PosE on or abouE December 6, 1991, and December 13, 1991. In addition, a Not,ice of Changes will be published in the Federal Register. As required by Ehe legislaEion, a communit,y must adopt and enforce floodplain managemenE measures Eo ensure conEinued eligibility to part,icipate in Ehe NFIP. Therefore, your communit.y must, enforce t.hese regulations using, at a minimum, the BFEs, zone designaEions, and floodways in t.he Special Flood Hazard Areas shown on E.he FIRJ'{ and FBFM for your communiEy, including the previously described modificaEions. This response uo your request is based on minimum floodplain managemenE criEeria established under Ehe NFIP. Your communiEy is responsible for approving all proposed floodplain development,s, including this request,, and for ensuring EhaE necessary permits required by Federal or SEaEe law have been received. With knowledge of local conditions and in Ehe interesE of safeEyr SEaEe and communiEy officials may seE higher sEandards forconsEruction, or may limit development in floodplain areas. If the State ofColorado or CiEy of Glenwood Springs has adopt,ed more rest,ricEive or comprehensive floodptain managemenE crit,eria, t.hese criEeria Eake precedenceover t,he minimum _NFIP requirements. The community number and suffix code lisEed above will be used for all floodinsurance policies and renewals issued for your community on and afEer theeffective date listed above. The modifications described herein are effective as of the daEe of rhisleEEer. However, wichin 90 days of t,he second publication in Lne GlenwoodPostr your community may requesE Ehat. we reconsider Ehis deEerminaEion. Any request. for reconsideraEion must be based on scientific or Eechnical daEa.All int,erested parties are hereby notified rhat, uncil the 90-day periodelapses, Ehe determinat.ion may be modified. If you have any questions regarding Ehe modifica.tions described herein,please call the Chief, NaEural and Technological Hazards Division, Federal Emergency ManagemenE Agency, in Denver, Colorado, aE (303) 235-4g3Or orMr. Karl Mohr of my sEaff in tlashingEon, D.C., aL (ZO2) SqO-ZltO. Sincerely, ,rJ-!.^"R l--,r"-- William R. Locke Chief, Risk Studies Division Federal Insurance Administration Enclosures cc: Mr. PeEer Belau, P.E. ENARTECH, Inc. ,/me Honorable Marian Smith Chairperson, Garfield CounEy Board of Commissioners (r', L)z \-oLO zr{J O EIEJ ?t- =f;t 3l 8lc(rol "tJ I UJzoN =u(fZuJalF-zooo J L U o3 F G IJJ J f ooz9;ltt!a? UF>zoOOO SAIU0 USTNSf, o UJzoN H,E9E :J LrI.Id : 6l-tJJ (u, ,-rLr'f LLl :?: :r El !flEHr=EsO t co h.laH & o u,zoN coro 0t0 1 't3NVd SNtOf t EtaaI bIlrl {l! E: d 5 == '4= == f;;*E = =<E t <+€ =>= --=--c,(J 6 F a_( Foe)zO6odFz ri<Oc cai<lxo!F? 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Consuttins Engineers and Hydrotor^ts ffl?m' lii i tvlt (Jl":, May 16, 1.991 Mr. William R. I-ocke Chiel Risk Studies Division -\SVZZ- Federal Insurance Administration -ZArxs-_ il;*fi1-""1"'3.;:ry^Tagement Agencv ZtN 65 POST, Case No. 91-08-15P Mitchell Creek, Glenwood Springs, CO Dear Mr. I-ocke: Please find enclosed the following additional data to support our request for a map revision as requested in your letter dated April 23,l99l: Computer printout of the multiple profile }IF,C-? model including the total discharge at the Donegan Road bridge (Cross-sections 11.1 and 11.2) and the new Center Drive bridge (Cross-sections 6.L and 6.2). Floppy disk with the input and output files of the IJ.EC-? model for both subcritical and supercritical analyses. The flow is supercritical in the modeled reach. Certified As-Built Plans for the Center Drive bridge. Topographic map delineating the proposed 100-year floodplain and the floodway boundaries. When modelling the bridge at Donegan Road (Cross-sections 11.1 and ll.2),I discovered that the original HF,C-? model prepared by Simons and Li was based upon incorrect topographic data. I substituted field-surveyed data to correctly model the bridge opening. The revisions that have been made to Simons and Li's original H.F;C-} model are as follows: . Correct topographic data, based upon field surveys, was provided for Cross- sections 11.1, 1.1.2, L2, \3,14 and 15.. Cross-sections 13.7,13.2,14.1 and 14.2were included at the request of John Lui.. Cross-sections 6.1, 6.2,6.3 and 6.4 were included to model the new Center Drive bridge. The remainder of Simons and Li's original }IE;C-? model remains unchanged. a a 302 Eighth Strcet. Suite 325 P.O. Drawer 160 Glenwoocj Sp,ngrs. Colorado 81602 (303) 945.2236 Mr. William R. I-ocke Page - 2 The 100-year floodplain and floodway boundaries coincide through the study reach (Cross- sections 6.1 through 15) because the l0Gyear flow in contained entirely within the stream channel. However, at Cross-sections 13, 13.2 and 13.2, the elevation of the left overbank area is below the l0Gyear water surface elevation. The HEC-2 analysis does not show any flow in this area because the left top of bank elevation exceeds the 100-year water surface elevation. I recommend that this area be designated as an area of shallow flooding, as shown on the enclosed map. The bridge at Donegan Road has sufficient capacity to convey the 100-year flood waters, but not the 500-year flood, which would overtop Donegan Road and flow south and east. The extent of the 500-year floodplain cannot be accurately delineated. The bridge at Center Drive can convey both the 100-year and 500-year flows. The Donegan Road bridge is a 9-foot span by 5-foot high box culvert. The Center Drive bridge is a 12-foot span by 4- foot high box culvert with a concrete floor. Please give me call if you have any questions regarding the enclosed information. Sincerely, ENARTECH, INC. Peter Belau, P.E. PB/des Enclosures John Lui, FEMA (w/enclosures) Brian Hyde, CWCB (w/enclosures) Irslie Klusmire (w/o enclosures) Mark Bean (w/o enclosures) Willis Parkison (w/o enclosures) $!%ffi. n2ffi2 (Locke) ] pnoposED tocYEAR MITCHELLCBEEK \,/ .' /,,, t//L ',,-a4- t.\ n \\ DONEGAN ROAD #x:m;*# 5OGYE/ FLOOD 7?1 r-'K-2?'--'-1 -\r;' ooz E,G at, oo =z UIJalro Eo -a^--ri \ PARKING {9 --F -G-^m. ENARTECH lnc. CO,VSULI'NO ENG'/VEEFS ANO HYDFOLOG'STS P.O. DRAWEn '@GtEl,/wooD spR,rvcs, coLoRAoo El@2 (3cJ) 94r22s6 MITCHELL CREEK FLOOD INSURANCE STUDY PROPOSED MAP REVISION MAY, 1gg1 - FLOODPI-AIN AND FLOODWAY / Ii I nf nrLrENr-------i-.- Peter Belau, P.E. PBldes Enclosures John Uou w/o Enclosures Brian Hyde w/o Enclosures I*slie Klusmire w/o Enclosures Mark Bean w/o Enclosures Willis Parkison w/o Enclosures Y22fi2(?26_01-A) 6[nr-truo couNTY July Vt, L99l ENARTECH tnc- Consutt, Mr. Williarn R.I-ocke Chiel Risk Studies Division Federal rn suranc€ Administration Federal Emergency Management Agency Washington, D.C. 2M72 RE: 65 POST, Case No. 91-08-15P Mitchell Creelg Glenwood Springs, CO Dear Mr. Locke: -\svzz- -ZA]N- ^ZIN. Please find enclosed the additional informaiion for our requesi for a map relision ior this project as per your letter dated June L4, 1991. Enclosed are two }IE,C-? computer outputs for the 10, 50, 100 and 500 year profiles (supercritical and subcritical flows), with Cross-Sections 1 through 4.2 included. The subcritical run is applicable for Sections 1 to 4.L. These Sections have the same computed water surface elevations as the original HEC-Z analysis (Exhibit 7A previously submitted). Also enclosed is a H.F;C-2 computer output for the floodway analysis (supercritical flow). This floodway analysis was based upon the 100-year flood elevation with no encroachments into the stream channel. Since there is virtually no overbank flooding from Sections 16 to 4.1, the l0Gyear floodplain and floodway coincide. Please give me a call if you have any questions or comments regarding the enclosed data so we c:ln discuss this matter. Sincerely, ENARTECH, INC. 302 Eighth Street, Sulle 325 P.O. Drawer 160 Glenwood Springs, Colorado 81602 (303) 945-2236 JUL 25 1991