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Copperstone FS-CS 890126The Honorable Lou Duggan Mayor of the City of Coppell P.O. Box 478 Coppell, Texas 75019 i Federal Emergency Management Washington, D.C. 20472 ~ Case No.: 0 989 Dear Mayor Duggan: This is in reference to a letter dated October 10, 1988, and a floodplain study submitted by Mr. Russell R. Doyle, P.E., City Engineer for the City of Coppell. In his letter, which was forwarded to us by our Region VI office, Mr. Doyle requested a conditional Letter of Map Revision (LOMR) for a proposed fill ~roject along Cottonwood Branch and Denton Creek on behalf of Jerry Parche Consulting Engineers. The submitted floodplain study entitled Flood- plain Reclamation Study on Cottonwood Branch and Denton Creek, dated October 1988, prepared by Jerry Parche Consulting Engineers, included the following: a description of the methodoloqies used; HEC-2 models of Denton Creek and Cottonwood Branch representing existing and proposed conditions; and delineations of the existing and proposed 100-year floodplain boundaries and the proposed regulatory floodway boundaries on a topographic map. Prior to the commencement of our review, we received the initial fee of $350.00 for processing a conditional LOMR request of this type. This fee was sufficient to cover the review and processing costs associated with this submittal. As explained in the submitted floodplain study, additional cross sections were inserted into the HEC-2 models for Denton Cree~and Cottonwood Branch (in the vicinity of Denton Tap Road), which are not reflected ~n the preliminary Flood Insurance Study (FIS) for the City of Coppell, dated September 22, 1988. These models are therefore the best available models and will be used as the new baseline models in order to evaluate the effects of the proposed project. It is important to note, however, that these submitted models incorporated a swale construction and floodplain fill project known as the Magnolia project. We have recently received a request for a map revision from your community regarding the Magno].ia project and are currently awaiting the submission of a ~ written maintenance agreement for this project as specified under Part 65.6 (a)(12) of the National Flood Insurance Program (NFIP) regulations. Therefore, the preliminary FIS will not be revised to reflect the updated existing conditio,~ until the aforementioned maintenance agreement is received. After reviewing the submitted data, we have determined that the proposed fill project meets the minimum floodplain management criteria of the NFIP. If the project is completed as proposed, the 100-year water-surface elevations of Denton Creek would remain unchanged except at cross section 34850 where an increase of 0.1 foot would occur. In addition, the 100-year floodplain and regulatory floodway of Denton Creek would be decreased as indicated in the submitted floodplain study. Also, if the project is completed as proposed, the 100-year water-surface elevations of Cottonwood Branch would increase (a maximum of 0.9 foot) and the 100-year floodplain and regulatory floodway would be modified as depicted in the submitted floodplain study. It is important to note that the increase in the 100-year water-surface elevations of Denton Creek and Cottonwood Branch are due to the placement of fill outside of the regulatory floodway of each stream. Please note that future revisions to the Flood Insurance Rate Map (FIRM) and Flood Boundary and Floodway Map (FBFM) or restudies of the flood hazards in this area could modify this determination. This determination is based on the 100-year flood discharges computed in the preliminary FIS for your community, and does not consider subsequent changes in watershed characteristics that would tend to increase flood discharges. The development of this project and other projects upstream could result in increased flood discharges, which, in turn, could result in increased 100-year flood elevations. Future restudies of your community's flood hazards would take into account the cumulative effects of development on flood discharges, and could therefore establish higher 100-year flood elevations in this area. This conditional LOMR is based on minimum floodplain management criteria established under the NFIP. Your community is responsible for approving all proposed floodplain developments, including the project upon which this request is based, and for assuring that necessary permits required by Federal or State law have been received. State and community officials, based on knowledge of local conditions and in the interest of safety, may set higher standards for construction or may limit development in floodplain areas. If the State of Texas or the City of Coppell has adopted more restrictive or comprehensive floodplain management criteria, these criteria take precedence over the minimum NFIP requirements. Please note the requirements for floodway revisions as outlined in NFIP regulation Part 65.7 (b)(1) (copy enclosed), which states that when a floodway change is proposed, a copy of a public notice distributed by the community stating the community's intent to revise the floodway, or a statement by the community that it has notified all affected property owners and affected adjacent jurisdictions must be submitted to the Federal Emergency Management Agency (F~A). This requirement must be addressed when requesting a map revision to reflect the effects of the completed fill project. we have enclosed a copy of Part 65 of the NFIP regulations, which further describes the nature and extent of the material needed to support a request to revise an effective FIS, FIRM, and FBFM. Compliance with the criteria outlined in this document will expedite FEMA's review process, thus allowing the effective FIS, FIRM, and FBFM for your community to be revised as appropriate, in a timely manner. Should you have any questions regarding this matter, please do not hesitate to contact the Chief, Natural and Technological Hazards Division of the Federal Emergency Management Agency in Denton, Texas, at (817) 898-9127 or Matthew B. Miller of our Headquarters staff in Washington, D.C., ~t (202) 646-3461. Sincerely, Chief, Risk Studies Division Federal Insurance Administration Enclosure cc: Mr. RuSsell R. 9oyle, P.E. Mr. Jerry Parche, P.E., Jerry Parch~ Consulting Engineers FEDERAL EMERGENCY MANAGEMENT AGENCY Revised as of October 1, 1986 Amendment No.1, June 30, 1987 National Flood Insurance Program and Related--Regula..tions Federat Emergency Jnagement Agency § 65.1 PART 65mIDENTIFICATION AND MAPPING OF SPECIAL HAZARD AREAS 65.]. PurDose of part. 65.2 De/initions. 65.3 Requirement co submit new c~hnic~ 65.4 ~ight to submit flew :~i~l d~. 65.5 Rev~ion [o s~ial h~d ~rez ~und- ~es with no ch~ge [o b~e flood eleva- tion ~e~e~a[io~. ~ ~ 65.5 Re~ion of b~e il~d elevation de[er- ~atio~. 65.7 ~way rev~io~. ~5.8 ~eview of proposed 65.9 ~eview ~d r~po~e by the A~/n~- t~Cor. § 65. I Purpose oi' par~. ~2 ~.S.C. ~10~ ~utborizes ~he Direc- tor to iden~y ~nd publi-~h ~n[or~nA- ~ion with respe¢~ :o ~11 a. re~ within the United States having special flood. 293 § 65.2 mud,slide (i.e., mudfiow) and flood-re- lated erosion hazards. The purpose of Chis part is to outline the steps a com- munity needs to take in order to ass/st the Agency's effort in providing up-to- date identification and publication, in the form of the maps described in Part 64, on special flood, mudslide (i.e., mudflow) and flood-related erosion hazards. i48 I~R 28278. June 21. 1983] § 65.2 Definitions. (a) Except as otherwise provided in this part, the definitions set forth in Part 59 of this subchapter ~re applica- ble to this part. (b) For the purpose of this par~, certification by a reff/stered profes- sional engineer or other party does not constitute a warranty or ~uarantee of perfo,.-m, ance, expressed or implied. Certification of data is that the data is accurate to the best of the certifier's knowledge. Certification of analyses is a statement that. the analyses have been performed correct- ly and in accordance with sound engi- neering practices. Certification of structural worl~ is a stat.ement that the work~ are designed in accordance with sound engineering practices to provide protection irom the base flood. Certilication of "as built" condi- tions is a statement that the s~ructureis) has been built accordin$ to the plans being certified, is in place. and is fully functioning. [51 1~ 30313, Aug. 25. 1986] § 65.3 Requirement to submit new techni- cal data. A cornmun/ty's base flood elevxtions may increase or decrease resulting from physica~ chtnges affecting flood- ing conditions. A~ soon as practicable, but not later than six months after the date such information becomes avtilable, a community shaU notify the Adrninistrator of the submitting technical or scientific d~ta in accordance with this part. Such submi~ion is neces,aa~ so that upon confirmation of those physic~l changes affectin~ flooding conditions. risk ~remium rates and flood plain management requirements will be based upon current dat~ 44 O:R,,~. I ( 1 O- 1-86 Edition) [51 PR 30313, Aug- 25. 19861 § 65.4 Right to submit new technical data. (a) A community has a right Co quest changes to any of the informa- tion shown on an effective map chat does not impact flood plain or flood- way delineations or base flood eleva- tions, such as community boundary changes, labeling, or planime~ric de- tails. Such a submission shall include appropriate supporting documentat.ion in accordance with this part and may be submitted at any time. (b) All requests for changes to effec- tive maps. other than those initiated by PE,M.A, must be made in writing by ~he Chief Executive Officer of the community (CEO) or a~ official desig- nated by the CEO. Should the CEO refuse to submit such a request on behall of another party, i~EMA will a~-ee to review it only ii written evi- dence is provided indicating the CEO or desiKnee has been requested Co do so. [51 PR 30313. Aug. 25, 19861 §65.$ Revision to special hazard a~ea boundaries with no chan~e to base flood elevation determinations. (a) Data requirements for topog'~'aph- ic chan~es. In many areas of special flood hazard (excluding V zones and floodways) it may be feasible to ele- vate areas with earth fill above the' base flood elevation. ~cientffic and technical ip. form~tion to support a re- quest to ~aAn exclusion from an of special flood hazard of a s~ructure or parcel of land ~hat has been elevat- ed by the Placement of fill shall in- elude the followin~ (1) A copy of the recorded deed indi- cating the legal description of the property and the official recordation information (deed book volume and pa~e number) and bearing the seal the appropriate recordation official (e.ff., County Clerk or Recorder Deeda). (2) If the property is recorded on plat map, a copy o! the recorded plat indicating bosh the location of the proper~y and the official recordation information (plat book volume and page number) and bearing the seal of the appropriate recordation official. 294 Federal Emergency~nagement Agency the property is not recorded on a plat map, copies of the tax map or other suitable maps are required to aid FEMA in accurately locating the prop- erty. (3) If a legally defined parcel of land is involved, a topographic map indicat- ing present ground elevations and date of fill. F~E,MA's determination as to whether a legally defined parcel of l~nd Is to be excluded from the area of special flood hazard shall be based upon a comparison of the ground ele- vations of the parcel with the eleva- tions of the base flood. If the ground elevations of the entire legally defined parcel of land are at or above the ele- vations of the base flood, the parcel may be excluded from the area of spe- cial flood h~zard. (4~ If a structure is involved, a topo- graphic map indicating structure loca- tion a,nd ground elevations including the elevations of the lowest floor (in- cluding basement) and the lowest ad- jacent grade to the structure. FIgMA's determination ~s to whether a struc- ture is to be excluded from the ~rea of special flood hazard shall be based upon a comparison of the elevation of the lowest floor (including basement) ~.nd the elevation of the lowest adja- cent grade with the elevation of the base flood. If the entire structure and the lowest adjacent gr~te ~re at or above the elevation of the base flood. the structure may be excluded from the area of special flood h~zard. (5) Data to substantiate the base flood elevation. Lf PEMA has complet- ed a Flood Insurance Study (FIS), that data will be used to substantiate the base flood. Otherwise, data provid- ed by an authoritativ~ source, such as the U.S. Army Corps of Engineers, U.S. Geological Survey, U.S. Soil Con- serva:ion Service, state and local water resource department~, or technical data prepared and certified by a regis- tered professional engineer may be submitted. If base flood elevations have not previously been established, hydraulic calculations may also be quested. (6) Where fill has been placed ix) raise the l~round surface to or above the base flood elevation and tile re- quest to gain exclusion from an area of special flood hazard includes more than a single structure or a single lot. it must be demonstrated that fill will not settle below the elevation of the base flood, and that the fill is ade- quate!y protected from the forces of erosion, scour, or differential settle-- ment as described below: (i) Pill must be compacted to 95 per- cent of the maximum density obtain- able with the Standard Proctor Test method issued by the American Socie- ty for Testinff and Materials (AST!Vi Standard D-698). This requirement applies to fill pads prepared for resi- dential or commercial structure foun- dations and does not apply to filled areas intended for other uses. (ii) Pill slopes for granular materials are not steeper than one vertical on one-and-one-half horizonCal unless substantiating data justifying steeper slopes is submitted. (iii) Adequate protection is provided fill slopes exposed to flood waters with expected velocities during the occur- rence of the base flood of five feet per second or less by covering them with grass, vines, weeds, or similar vegeta- tion undergrowth. (iv) Adequate protection is provided fill slopes exposed to flood waters with velocities during the occurrence of the base flood of ~reater than five feet per second by-az-moring them with stone or rock slope protection. (?) A revisiofl of flood plain delinea, tions based on fill must demonstrate that any such fill has not resulted in a floodway encroachment. (b) New to~oFra~hic dzzt~. The pro- cedures described in paz-a4,r~phs (a) (1) through (5) o[ this section may be followed bo request a map revision when no physical changes have oc- curred in the m~-ea of special flood hazm'tL when no fill has been placed. and when the naturai &,round eleva- tions, as evidenced by new topographic maps. more detailed or more accurate than those used to prepare the map to be revised, are shown to be ~bove the elevation of the base flood. (c) C~-rti/ic~iion re~irer~-n/~. The items required in pa.,-~r~phs (a) (3) and (4) and (b) of this section shall be certified by a registered professional engineer or licensed land surveyor. Items required in paragraph (a){$) of this section shall be certified by the 295 community's ~ permit official, a registered professional engineer, or an accredited soils engineer. Such certifi- cations · re subject to the provisions of § 65.2 of this subchapter. (d) Su~n~$~o~ ~roce~u~$. All quest~ shall be submitted to the appro- priate F~IVIA I~egional Office servicing the community's geographic area. [§I F~ 30313. Au~. 25, 1986] § 65.6 Revision of base flood elevation terminations. (a) Cre=e~'tzl conditfon~ =n~ dat= q=ire~engs. (1) The supporting must include all the information lr~E,MA need~ ~o review a~d evaluate the requesL This may involve ~he questor's performing new hydrologic and hydraulic analysis and delineation of new flood plain boundaries a,nd floodways, aa necessary. (2) To avoid discontinuities between the revised and unrevised flood data. the necessary hydrologic a,nd hydrau- lic · nalyses submitted by the map re- vision requestor mu~t be extensive enough to ensure that a logical transi- tion can be shown between the revised flood elevations, flood plain bound- ~-ies. and floodways a,nd those devel- oped previously for ~reaa not affected by the revision. Unlesa it is demon- strated that it would not be appropri- ate, the revised and unrevised base flood elevations must match within one-half foot where such tr'a~_sitions occur. (3) l~evisions cannot be made based on the effecta of proposed projec~ or future conditions. Section 65.8 of this subchapter contains provisions for ob- tnining conditional approval of pro- posed projecta that m&y effect map changes when they a~e completed. (4) The datum ~nd d~te of releveling of benchm~, if any. to which the elevations are referenced mu,st be indi- cated. (5) Maps will not be revised when discharges chan~e aa a result of the use of an alternative methodology or data for computing flood discharges unless the change is statistically nifica,nt aa measured-by · confidence limit~ a~nalysis of the new discharge es- timates. (6) In order for an alternative hy- draulic or hydrologic methodology 44 G~:~h. I (10.1-86 Edition) be accepted, any computer program used mu,st be accepted for i~eneral use by a ~ove~ental a~ency or notable scientific body. must be well docu- mented includin~ · ~er's ~d pro- ~mer's m~ual. ~d must be avail- able to the ~ene~ user. (~) A revised hydrologic ~alysis for flooding sources with established b~e flood etevatio~ m~t include evalu~- ~on of the s~e r~u~ence inte~l(s) studied in the effective ~S. such the ~0-. 50-, ~00-, ~d 500-year flood disch~ges. (8) A revved hydraulic ~alysis for flood~ source with established b~e flood elevations must inciude evalua- tion of the s~e recu~ence inte~al(s) studied in the effective ~S. such the 10-, 50-, ~00-. ~nd 500-year flood elevation, and of the floodway. Unle~ the b~is of the request ~ the use of ~ ~te~a~ive hydraulic methodology or the requestor c~ demo~trate tha~ the data of the o~ginal hyd~uiic com- puter model ~ unavailable or i~ ~e is ~approp~ate. the ~ysis sh~l be made ~in~ the s~e hyd~ulic com- puter model ~ed to develop the b~e flood elevatio~ sho~ on the effec- tive ~ood ~u~ce ~te ~p ~d updated to show present conditions in the flood pl~n. Copies of the input ~d output dat~ from the o~n~ ~d ~vised hyd~ulic ~alyses shall be submitt~. (9) A hy~olo~c or hy~ulic ~y- s~ for a.flood~ source without es~b- ~hed b~e flood elevatio~ may be ~o~ed for o~y the 100-ye~ flood. (10) A rev~ion of flood plan delinea- tto~ b~ on topo~phic ch~es m~t demo~t~e that ~y topo~ph- ic ch~es have not resulted in floodway encro~hment. (11) Delin~tio~ of flood plan ~~es for a floodin~ source with ~bl~h~ b~e flood etev~tio~ p~vide both the 100- ~d 500-year flood ~l~ boodles. For flooding ~u~es ~thout ~t~bl~h~ b~e flood' elevation, o~y lO0-year flood bound~es need be submitted. Thee boodles should be shown on · to~o- ~hic m~ of suitable scale ~d con- tour inte~al. (b) Data re~uir~en~ /or co~ciing map e~. To corr~t e~o~ in the o~ginal flood ~alysis. technical 296 Federal Emergency/'%nogement Agency submissions shall include the follow- in~ (1) Data identifying mathemaucal errors. (2) Data identifying measurement erro~ ~d providin~ co~ec~ me~ure- ment~. (c) Da~a requirements for changed physical conditions. Revisions b~ed on ~he effec~ pi physical cnsn~es h~ve occurred in ~he flood plain sh~l include: (1) ~anges ~ff~c~ng h~o~o~c con- ~i~on~. The followin~ da~ m~ be submitted: (i) General description of ~he ch~es (e.~.. d~, diversion chapel, or detention (ii) Co~ruc~ion plans for ~-buil~ condition, if (iii) ~ew hydrologic analysis counCin~ ~or ~he e~ec~s of ch~es. (iv) New hy~s~ic ~lysis ~d pro- files ~m~ the new flood discharge v~lues r~uitm~ from the hydrologic ~ys~. (v) ~ev~ed del~e~tio~ of ~he flood plain boodles ~d (2) ~anges affecting h~drauiic con- dittos. The following d~:~ sh~ be submitted: ii) Gene~ d~c~ption of :he ch~ges (e.g.. ch~nel~tion or new b~dge, c~ve~, or lev~). iii) Co~:~ction pl~ for ~-buil: condition. (ih) ~ew hyd~uHc ~ys~ ~d flood elevation 0rofiles ~ounting ~or the eH~ of :he ch~ges ~d ~ing :he o~n~ flood d~ch~rge v~ues upon which :he o~gin~ map ~ b~ed. (iv) Re,ed delinea:io~ of :he flood pla~ boodles ~d floodway. (3) ~anges involvin~ congitio~. ~e following d~ta sh~ll be submit:cC ii) Gene~ description of ch~ges (e.g., ~g or flying). (ii) New ~opo~ohic ~o~a~ion. such ~ soot elevation, c~ secUo~ ~d~g pl~, or contour m~0s. (iii) ~evised deline~:io~ of :he flood 0lain boodles ~d, ii n~e~ary. floodway. (d) Data requir~M for inco~o- ~tin~ imp~ved dat~ ~eques~ for re- ~io~ b~ed on :he use of improved hydrologic, hydraulic, or topographic data shall include the following data: (1) Data that are believed to be better than those u~ed in the original ~.nalysis (suc.~ ~-~ additional years of stream g~ge data). (2) Documentation of ~he source of the data. (3) Explanation ~ ~o why ~he use of the new data ~ill improve the results of the original ~lysis. (4) Revised hydrologic ~lysis where hydrologic d~ ~e ~eing incor- porated. (5) Revised hydraulic ~lysis ~d ~ood elevs~ion profiles where new drologic or hydrsulic ds~ ~e ~eing incorporated. (6) Revised delineations o[ ~he flood plain boundsries ~nd floodway where new hydrologic, hyd~ulic, or :ooo- graphic d~ are ~ein~ incoroo~ed. (e) Da~a requirem~M for i~co~o- rating improved me~o~. ~eques~ for revisio~ b~ed on rhe ~e of im- proved hydrologic or hydraulic meth- odology shall ~clude ~he following da~a: (1) New hydrologic ~alys~ when ~ema:ive hydrologic methodology being proposed. (2) Hew hyd~ulic ~alys~ ~d flood elevation profiles when ~ ~ema~ive hyrologic or hyd~ulic methodology being prooosed. (3) Ex9l~a:ion ~ ~o why :he ~ter-: native methodolo~es ~e supeNor :he o~n~ methodolo~es. (4) Revved detinea~io~ of the ~ood plain boundaries ~d floodway b~ed on :he new ~alysis( es ). (f) Certification ~quir~. ~ys~ ~d d~ submitted by the re- ques:er sh~ ~e ce~i~ by a re~- :ered profe~ional en~eer or 1ice.ed l~d su~eyor, ~ ~OOrop~a~e, subject :o ~he definition of "~ific~ion" ~ven ~: ~ 55.2 of ~h~ subchap~er. (g) Submizzion p~cedu~z. ~1 ie- ques~ sh~ be submi:t~ :o ~he ~o~ro- priate ~ Re~onal Offi~ se~icing ~he co~uni~y's g~ohic ~. [51 ~ 303~. Aug. 25. I986] § 65.7 Floodway revisions. (a) General F~oodway data is devel- oped as part of i~EM~ Flood Insur- ance Studies and is utilized by commu- 297 § nities to select and aaopt floodway$ as part of the flood plain management program required by § 60.3 of this sub- chai~ter. When it has been determined by a community that no practicable al- ternatives exi-~t to revising the bound- aries of its previously adopted flood- way. the procedures below shall be fol- lowed. ( b ) Data requirements when base !lood elevation changes are requested. When a floodway revision is requested in association with a change to base flood elevations, the data require- men;s of § $5.5 shall also be applica- ble. In addition, the following docu- mentation shall be submitted: (1) Copy of a public not-ice distribut- ed by the community stating the com- munity's intent to revise the floodway or a statement by the community that it has notified all xffected property owners and a~fected adjacent jurisdic- tions. (2) Copy of a letter notifying the propriate State agency of the flood- way revision when the State has juris- diction over the floodway or its adop- tion by communities participating in the N'FIP. (3) Documentation of the approval of the revised floodway by the appro- priate State agency (for communities where the State has jurisdiction over the floodway or its adoption by com- munities participating in the NFIP). (4) Engineer/rig analysis for the re- vised floodway, as described below: (i) The floodway analysis must be performed using the hydraulic com- puter model used to determine the proposed base flood elevations. (ii) The floodway limits must be set 'so that neither the effective base flood elevations nor the proposed base flood elevations if le.~ than the effective base flood elevations, are increased by more than the amount sOec/fied under § $0.3 (d)(2). Copies of the input and output data from the original and modified computer models must be submitted. (5) Delineation of the revised flood- way on the same toOographic map used for the delineation of the revised flood boundaries. (c) Data requi~t~ for chanqes not a~ociated with ba~e flood ciera- 44 C~:R Ch. I (10-1-86 Edition)' tion chanqes. ~,¢ following data shall be submitted: (1) Items described in paragraphs (b) (I) through (3) of th/s section must be submitted. (2) Engineering anal.vs/s for the vised floodway, as described below: (i) The original hydraulic coml~uter model used to develop the established base flood elevations must be modified to include alt encroachment~ tha~ have occurred/in the flood plain since the existing floodway was developed. If the or/ginal hydraulic computer model is not available, an alternate draulic computer model may be used provided the alternate model has been calibrated so as to reproduce the origi- nal water surface profile of the origi- nal hydraulic computer model. The al- ternate model must be then modified to include all encroachments that have occurred since the exmting flood- way was developed. (ii) The floodway analysi-~ must be performed with the modified comput- er model using the desired floodway. limits. (iii) The floodway limits must be set so that combined effec~ of the past encroachments and the new floodway limits do not 'increase the effective base flood elevations by more than the amount specified in § 60.3(d)(2). Copies of the input and output dst& from the original and modified com- puter modem must be submitted. '~ (3) Delineation of the revised flood: way on a copy of the effective ~ map and a suitable topogr~hic mal~. id) Certi/icatlon requirements. All analyses submitted shall be certified by a registered professional engineer. All ~opographic data shakl be certified by a reIFL~tered profe~ional engineer or licensed land surveyor. Certifica- tions are subject to the definition given at § 55.2 of this subchapter. (e) Submission procedures. All ?e- quests that involve cl-mx~es to flood- ways shall be submitted to the pria~e ~ Regional Office servicing the community's geogravhic area. [51 ~ ;10315, Aug. 25, 198~] § G$.~ ~,Review of proposed projects. A community, or individual through the community, wishing i~EMA's com- 298 Federal Emergenc~y/"~nagement Agency menu on whether a proposed project. if built ~s proposed, wouJd jusl~ify map revision may request a Condition- al Letter of Map Amendment or Revi- sion in accordance with Part 72 of subchzp~er. The dzta required to sup- port such reques~ ~e the s~e ~hose required to support reques~ for rev~io~ in ~ccord~ce ~ith ~ 65.5. 65.6, ~d 65.7. except ~-built certifica- tion ~ not required. [51 ~ 30315. Aug. 25. 1986] ~ 65.9 Review and r~nse by the Admin- ist~tor. If ~y quesUo~ or problems ar~se d~ing review, ~{ will co~ult ~he Ch~e~ Execu[ive Officer o~ cbe commu- nity (CEO), ~he community official desi~z[ed by the CEO, ~nd/or ~he re- quester for resolution. Upon receip~ of ~ revision request. ~he A~inis[r~[or sh~ll mail ~ ac~owled~en~ of re- cei~ of such reques% ~o %he CEO. Within 90 days of receiving ~he re- ques~ with ~ll nece~y ~o~ion, ~he A~inm~or sh~l notify :he CEO of one or more of ~he followm~: (~) ~e effective m~D(s) sh~l no~ be modified; (b) ~e b~e flood elev~tio~ on ~he eff~tive ~RM sh~l be modified new b~e flood eleva~io~ shall be es- ~bl~h~ ~der :he pro~io~ of P~ 67 of ~his subch~te~ (c) ~e ch~es r~ues~ are ~D- proved ~d ~he ma~(s) ~ended ~%ter of Mzp Rev~ion (LO~); (d) The ch~ges r~ues~ proved ~d · revved mGp(s) will be p~nted ~d d~t~buted; (e) The ch~es r~ues:ed ~e not such z si~ifi~t ~ture ~ tq ~ ~u~ce or rev~ion of the flood in- sure study or mzDs ~d will be de- fe~d ~til such time ~ · si~ilic~: c~ge occur: (f) ~ ~tion~ 90 days ~ r~uired . ~ ev~uate the ~ientific or Cechnic~ ~ sub~tt~; or (g) Ad~tion~ ~ ~e r~uir~ ~o suv~n ~he ~ion r~uest. [51 ~ 30315. Aug. ~. 1986] ~.10 MappinK of ~ p~t~t~ by lev~ (~) ~~ Pot 9u~oses of the ~, ~ wffi o~y r~o~ize in flood hazard and risk mapping effort those levee systerrm that meet, and continue to meet, m/n/mum design, op- era:ion, and maintenance standarcis that are consistent with the level of protection sought through the com- prehensive flood plain management criteria established by § 60.3 of this subchapter. Accordingly, this section describes the ~ypes of information FEM~ needs to recognize, on NFIP maps, that a levee system provides protection from the base Flood. This information must be supplied to F~EIVIA by the community or other party seeking recognition of such a levee system at the time a flood risk study or restudy is conducted, when a map revision under the provisions of Part 65 of this subchapter is sought based on a levee system, and upon re- quest by the Administrator during the review of previously recognized struc- tures. The FEMA review will be for. the sole purpose of establishing appro- priate risk zone determinations for Nlm[1: maps and shall not constitute a determination by FEMA as to how a structure or system will perform in a flood event. (b) Desiira criteria. For levees to be recognized by FE.B/LA. evidence tha~ adequate design and operation and maintenance sys:ems are in place to provide reasonable assurance Chat pro- tection from the base flood exists: must be provided. The following re- quirements must be met: (1) Freeboard. (i) Riverine levees must provide a minimum freeboard of three feet above the water-surface level of the base flood. An additional one foot above the minimum is re- quired within 100 feet in either side of structures (such ~s bridges) riverward of the levee or wherever the flow is constricted. An additional one-haM foot above the minimum at :he up- s~;rearn end of the levee, tapering-to not le~ than the minimum a~ the dowr~tream end of the levee, is ~l~o required. (ii) Occasionally, exceptions to the minimum riverine freeboard require- ment described in paragraph (b)(1)(i) of this section, m~y be approved. Ap- propriate engineering an~yses demon- str~ting aziequate protection with a lesser freeboard must be submitted to 299 § 65.10 44 C~:~'~'~. I (10-1-86 Edition) support a request for such a.n excep- tion. The material presented must evaluate the uncertainty in the esti- mated base flood elevation profile and include, but not neceasarily be limited to an a.~sessment of statistical confi- dence limits of the lO0-year discharge: changes in stage-discharge rei.~tion- ships; a.nd the sources, potential, and magnitude of debris, sediment, and ice accumulation. It must be also shown that the levee will remain structurally stable during the base Hood when such additional loading considerations are imposed. Under no circumstances will freeboard of less th.~n two feet be accepted. (iii) For coastal levees, the freeboard must be estaOlished at one foot above the height of the one percent wave or the maximum wave runup (whichever is greater) associated wi~h the lO0- year stillwater surge elevation at the site. (iv) Occasionally, exceptions to the minimum coastal levee freeboard re- quirement described in paragraph (b)(i)(iii) of this section, may be proved. Appropriate engineering anal- yses demonstrating adequate protec- tion with a lesser freeboard must be submitted to support a request for such an exception. The material pre- sented must evaluate the uncertainty in the .estimated base flood !oading conditions. Paxticular emphasis must be pl~ced on the effec~ of wa~'e attack and overtopping on the stability of the levee. Under no circumstances, howev- er, will a freebom'd of less tha~ two feet above the 100-year stillwater surge elevation be acce~ted. (2) Closures. All openin~ must be provided with closure devices that axe structural parts of the system durin~ overation ~nd design ~ccording to sound engineering pre. trice. (3) Emhankrnertt protection. Engi- neering anaJyses must be submitted that demonstrate that no appreciable erosion of the levee embankment ca~ be expected during the base flood, ~s a result of either current~ or waves, and that anticipated erosion will not result in failure of the levee embankment or foundation directly or indirectly through reduction of the seepage path and subsequent instability. The fac- to~ to be addressed in such analyses include, but axe not limited to: Expect- ed flow velocities (especially in con- st~:icted areas); expected wind and wave action; ice loading; impact of debris; slope protection techniques; duration of flooding at v~rious stages and velocities; emba.ukment and foun- dation materials; levee alignment. bends. ~d t~itions; ~d levee side slopes. (4) Embank~t ~nd foundation stability. ~gineering analyses that evaluate levee emb~ment stability must be submitted. The analyses pro- vided shall evaluate expected seepage during loading conditions ~socia~ed wi~h ~he b~e flood and shall demon- strafe ~ha~ seepage imo or ~hrough ~he levee foundation and embankment will not jeopardize embankment or foundation stabiligy. An alternative analysis demonstrating ~h~t ~he levee is deMgned and constructed for stabili- gy against loading condition~ for I~ ~ defined in ~he U.S. Amy Co~s' of gngin~m (COE) m~ual. "Dezi~ ~d Co~tmction of Levees" (~M 1110-2-1913, Chapter 6. Section II), may be used. ~e f~cto~ tha~ shall be addre~ed in the ~yses include: De,th of ~ood~g, duration of 5ood- mt, emb~ent geomet~ ~d len~h of seepage path ~t c~tic~ lop,ions. emb~ent ~d fo~d~tion materi- als. emb~ent commotion, ~ene~- ~io~, other d~i~ f~to~ ~f~ting seepage (such ~ d~e l~ye~). ~d other desi~ f~to~ ~fecting emb~k- merit ~d foundation stability (such be~). (5) Set~L ~ee~ng ~yses m~t be sub~tt~ that ~e~ the po- tenti~ ~d m~itude of future lo.es of freehold ~ a ~t of levee settle- men~ ~d demo~t~te th~ fr~o~d ~11 be m~n~ with~ the m~i- mum st~d~ ~ fo~h in p~~h (b;(1) of t~ ~tion. ~ ~lysis m~t add~ emb~ent loa~, com- pre~ibility of emb~en~ ~i~, com- pre~ibility of foundation soil, age the levee system, ~d co~t~ction commotion method. ~ ~ddition. de- g~iled settlement ~ysis using ~roce- dures such ~ those desc~bed in the fOE m~ual. "Soil Mechanics Desi~e~tlement ~alysis" (EM 1100-2-1904) m~ be submitted. 300 Federal Emergency A ,agement Agency 6:5.1o (6) fntewior druin~ge. An analysis must be submitted that identifies the source(s) of such flooding, the extent of the flooded a~ea~ and, if the average depth i~ KreaSer tha~ one foot, the water-su~ce elevation(s) of the b~e flood. Th~ ~alys~ m~t be b~ed on the joint probability of ~terior ~d exte~or flood~K ~d the ca~city of f~flities (such ~ drainage l~es ~d' ~s) for ev~ua~inK ~te~or flood- w~e~. (7) O~e~ ~ c~ ~ ~ique situation, such ~ those where the levee s~stem h~ ~tatively hiKh ~l- ne~bili~y. ~ may require ~ha~ other desi~ crite~a ~d ~alyses be submitted to show that the leve~ ~ro- vide adequate ~rotection. ~ such situ- ation, sold en~eer~g ~ctice will be the st~d~d on which ~ will b~e i~ dete~inatio~. ~ will ~o provide the ~tion~e for ~g th~ ad~tion~ ~fo~a~ion. lc) O~e~tion ~ia~ and c~ ~or a lev~ system to be r~o~ed, the ove~fio~ ~te~a m~t be ~ de- ~bed below. ~1 dos~e de~ces or m~h~i~ s~te~ for ~te~ ~e, whether m~u~ or automatic, m~t be o~e~ed ~ ~cor~ce ~th ~ offici~y ado~t~ m~u~; a co~y of which m~t ~ ~- ~d~ ~ ~ by the ove~to~Nhen lev~ or ~~e system ~o~on be~ ~ught or when the m~ for a pre~o~ly r~~d s~tem m~t be ~der ~e j~ction of a ~e~ or S~ ~ency. ~ ~ency ~ted by ~e~ or S~ law, or ~ency of a co~ty ~e~. /1) ~~ Ove~flon ~l~ for s~ m~t ~dude ~e follo~ ii) Docmen~tion of ~e flood ~ s~m, ~der the j~c~on of ~at ~ ~ ~ ~ ~er eme~ency ove~on ~ti~ ~d demolition ~ ~ficient fl~d w~ t~e e~ for the comvleted ove~fion of ~ clos~ st~ct~. ~clu~ n~e~ ~ se~. befo~ fl~wate~ ~h the b~e of the close. iii) A fo~ ~l~ of over,ion clu~ sD~ffic ~tio~ ~d ~i~- men~ of ~vo~ibiBty by ~di~du~ ~e or ~tle. (iii) Provisions for periodic oper- ation, at not less than one-year inter- vals. of the closure structure for test- lng and training purposes. (2) fnte~or drainage s~ste~. Interi- or d~in~e syste~ ~ocizted with levee syste~ ~u~ly include stooge · re~. ~avity outlet, pumping tions, or · combination thereof. These drsinage syste~ will be reco~ized by ~ on NFIP ma~s ior flood ~roCec- :ion p~oses only if :he iollowtng mm~ cnteri~ ~e included m :he o~e~:ion ~1~: (i) Docmenta:ion of ~he flood lng system, under ~he jurisdiction of Feder~. State. or co~uni~y officials. ~h~t will be ~ed go ~rigger emergency opers~ion activities ~d demonstrs~ion tha~ sufficient flood w~rning time exists ~o pemR ~ctivstion of mecha- nized portions of the drsin~ge system. (ii) A formal pl~ of open,ion cluding specific-~tions ~nd ~si~- men~ of res~o~ibility by individual n~e or title. (iii) ~ovision for m~u~ b~ckuD for the ~tiv~tion of ~utoma~ic syste~. (iv) ~ov~io~ for pe~odic ~ec- tion of ~te~or ~in~ge syste~ ~d periodic oDe~tion of ~y mech~ed ~o~io~ for test~g ~d tr~i~ng Dur- poses. No more th~ one year shall elapse between either the ~tio~ or the ove~io~. (3) 0~ o~e~lion ~la~ ~n~ c~te- ~ Other ovemtin~ ~l~ ~d crite~ ~y be requMed by ~ to e~ure thzt ~dequa:e ~t~tion ~ ~rovided s~ffic situation. ~ such ~es, sold emergency ~agement ~mc- rice ~H be the s~d upon which ~ dete~tio~ ~ be b~ed. id) M~i~t~ance ~la~ ~d ~te~ For Iev~ syste~ ~ be r~o~ed p~~ V~t~tion f~m the b~e flood, ~e m~ten~ce c~te~a be ~ d~bed hereto. Lev~ m~t be m~t~ed ~ ~cor~ce ~th ~ offic~y ~opted m~te- n~ ~1~ ~d a cory of thM ~I~ m~t be ~ded to ~ by the o~er of the lev~ s~tem when nition ~ be~g~ sought or when the pl~ for · ~revio~ly reco~ed system M revved in ~y m~er. m~[en~ce ~tivities m~t be ~der :he j~diction of · Pede~l or Sta~e ~ency, ~ ~ency cr~t~ by Pede~ 301 44 C]:R Ch. ! (10-1-86 EditiorO § 65.11 or State law. or an agency of a commu- nity participating in the NPTP that must as.sume ultimate responsibility for maintenance. This pl~'~ must docu- ment the formal procedure that en- sures that the stability, height, and overall integrity of the levee and i~ a.~ociated structures and systems are maintained. At a minimum, mainte- nance plans shall specify the mainie- nance activities to be performed, the frequency of their performance, and the person by name or title respor~si- ble for their performance. (e) Certification req~ziremen~. Data submitted to support that a given levee system complies with the struc- tural requirements set forth in para- graphs (b)(1) t,hrough (?) of this sec- tion must be certified by ~ registered professional engineer. Also, certified a.s-built plans of. the levee murat be sub- mitred. Certifications are subject to the definition glven mt § 65.2 of this subchapter. In lieu of these structural requirements, a Federal agency with responsibility for levee design may cer- tify that the levee hms been adequate- ly designed ~nd constructed to provide protection against the b~se flood. [51 ~ 30316. Aug. 25, 1986] §6.5.11 List of communities submitting new technical dam. Thi~ section provides · ctunulative li~t of communities where modifica- tions of the ba~e flood elevation deter- min~tiorm have been made because of sub--ion of new ~ien:ific or t~i- c~ data. Due to the ne~ for expedit- ~g :he modification, the revved m~ M ~eady in effect ~d the ~pe~ period commenc~ on or ~ou: the ef- f~tive date of the modified ma~. ~ ~te~m ~le, lo,owed by · fin~ ~le, wi~ l~t the revved map effective ~:e, Ioc~ ~osi:ory ~d the n~e ~d ~- ~e~ of the Chief ~u~ve Officer of the co~iCy. ~e ~D(~) ~ (~e) ~- f~tive for both flood pl~ m~e-. ment ~d ~u~ce ~~. [51 ~ 30317, Au~. 25, 1988] ~ ~al~ No~ Pot a l~t of co~uniti~ ~u~ ~der th~ s~tion ~d nog ~ ~ the ~. ~ the ~t of ~'S~io~ ~- f~d avv~n~ in the ~n~n~ Ai~ ~ion of ~h~ vol~e. 302