KEY HAVEN ESTATES BASIN A Drainage Calculations Project Area Pavious Area lmpervbus Area % Impervious Rsinfan for 2Syrl24hr event (P) Rainfall for 25yrTJhr event (P) Depth to Water Table Developed Available Storage -1 Stwage (S) proiect Pervkus Arm Impsrviarsh % Imm Rainfall for 25yrL24hr went (P) Rainfall for 25yrBhr event (P) Devdopad AveitabkStwase soil Storage (S) Vdume = QA PmSsct Area Roof Area lmpervkus Area % Impervious (Excluding Roof Am) A) One inch d Rlnon lrwn drainage basin Water QuiwfW Vs. WeW Que$ll! RiiJ. MM,PE -15 201 Front St., Suite 207 Key west. FL 33040 KEYHAVENESTATES BASIN A STAGE-STORAGE TABLE - BASIN A Assumptions: Site storage is linear, starting at min. road elev 4.0 up through slab elev.5.0. From elev. 5.0 to 5.5 storage is vertical. stage Site Grading ac-lt acin 4.0 0 0 4.5 ((.5/1) x 4.65 ac) x (.5 fV2) = 0.58 6.98 5.0 ((1/1) x 4.65 ac) x (1 fU2) = 2.33 27.90 5.5 (0.5*4.65)+((1/1) x 4.65 ac) x (1 ft12) = 4.65 55.80 Runoff Volume from 25yrMay 39.5 ac-in The zero discharge stage for the 25yrI3day storm is interpolated from the stage storage table. The minimum perimeter elevation is 5.19 R Richard J. Milelli 201 Front St.. Suite 207 L-- Key West, FL 33040 QE~$Y( KEYHAVENESTATES BASIN B Dminage Calculations Water QuanbW - Predevelo- Pmjact Area Pervious Area Impenrkus Area % Impsrvious R8blfan for 25yrR4hr went (P) Rainfall for 25y1/3hrwent (P) Depth to Water Table Developed Available !Storage soil SEwaga (S) Pmjact Ana Pervkush lmpaviow Area % Imparvbus Rainfall for went (P) RainfaH fa2!5yl13hr wart (P) Dapth to WdaTa#e Devebpad Avaitmbb Storage Storage (S) Volume = QA Projact Aroa Roof Area lmpenrious Area % lmpsrvious (Exdudlng Roof Area) A) Thm quaftm lnch of Mlon from balnage basin Water QuanlilYv Vs. Water Qu* -0.34 adn < 0.78 adn I Water Quality 50% 3630 Rictrard J. MlM, PE #58315 201 Fmnt St, Suits m Key west, Fkrida 33040 KEYHAVENESTATES BASIN C Drainage CalcuIetiom Project Arsr Pavious~ Irnpsrvias Area % Impervious Rainfail for 25yrR4hr event (P) Rainfan for 25yrm svsnt (P) Dsplh to Water Table Dwdaped A~bSlapge soil Staage (S) Water Quentit~- Postdevdoamed Project Area Pmhous Arm Imperv#us Area % Impervious RPinhll for 25yrR4hr evsnt (P) Rainfall for 25yr13hr went (P) Do@ to Water Table DevebpdAvailaMbSt#age soil stuage (S) Water QueIi& Project Am Roof Area lrnparviaus Area % lmperviars (Exdudi Roof Arm) Wetar Quentitiv Vs. Weter Quelity Swale Volume Rewired Water Quality '50% '3630 Swele Vdume Provided RimJ. MM 201 Front St, Suite 207 KeyWesfFL33040 pc~1 r - ,(< lol KNHAVENESTATES BASIN C STAGE-STORAGE TABLE - BASIN C Assumptions: Sie storage is linear, starting at min. road elev 4.0 up through elev.8.0 Stage Site Grading acR acin 4.0 0 0 4.5 ((.5/1) x 14.10 ac) x (-5 fV2) = 1.76 21.17 5.0 ((111) x 14.10 ac) x (1 fV2) = 7.06 84.66 5.5 (0.5*14.10)+((1/1) x 14.10 ac) x (1 Pt/2) = 14.1 1 169.32 Runoff Volume from 25yrMday 125.91 ac-in The zero discharge stage for the 25yr/3day stom is interpolated from the stage storage table. The minimum perimeter elevation is 5.20 R Richard J. Milelli 201 Front St., Suite 207 Key West, FL 33040 fg{e.slr ENCHANTED ISLAND BASIN D Drainage Calculations Roiath Pelviomh Impervious Area % lmpenrious Roiath PelviomArw Impervious Am I- % I- Rainfall for 25yrR4hr ernnt (P) Rainfall for 25yrM (PI Ro$dh Rodh Impenrkus Ama % lmpervkus (Excluding Rod Arm) Richad J. Midi. PE -15 201 FrnSt., SuRe 207 KeyWest.Florida33040 Mr. E. David Femandez Utilities Director City of Key West ,: 5701 College Road Key West, Florida 33040 Subject Technical Memorandum No. 1, Estimation of Drainage Well Capacities for the City of Key West Dear David: Enclosed are five final copies of Technkal Memorandum No. 1 for your use. Feel free to call me should you have any questions. As noted, I have forwarded copies of this technical ntemorandurn to Annalise and Janet. Sincerely, Kenneth F. WiIliams, F.E. c Annalise Mannix-Lacher/ Key West JanetMuccino/Key West Steve Hillberg/CHUn HILL Mitch Griffin/CHZM HILL Rick OIson/CH2M HILL Dave McNabb/CHZM HILL Stanley Fardm/CH2M HILL TECHNICAL MEMORANDUM 1 C-MHILL Estimation of Drainage Well Capacities for the City of Key West -ED WR: City of Key West PREPlWD By: CH2M HILL 4 DATE: April 19,2002 Contents Background................................................................................................................................ 1 Tidal Influence .............................................................................................................................I Estimated Well Capacity ............................................................................................................. 5 Pressurized Drainage Wells ...........................................................................................6 Gravity Drainage Wells ..................................................................................................6 Conclusions.................................................................................................................................. 7 Background The City is planning to add both gravity and pressurized drainage wens to its Stomwater Disposal System. The capacities of these wells must be estimated to design the stonn water pumping system and to estimate the contributions these facilities wilI make to the City's storm water drainage system. Initially, it was proposed to estimate the capacity of the propoeed pressurized drainage wens by performing capacity tests on existing drainage wens. However, during the initial data gathering phase for these projects, data from well completion reports on gravity was installed in the Peary Court area in 1993 were made available to CH2M HILL The permeability test results demonstrated at these web is considered to be consistent through- out the island. These wen completian reports contained drawdown versus flow information for each well. CH2M HILL concluded that the capacity testing that was initially proposed was not able to provide Mter information than that already documented in the existing well completion reports. Therefore, well capacity will be estimated using the data from the Peary Court wells. Tidal lnffuence Capacities of both pressurized and gravity drainage wells are influenced by the tides. Consequently, tidaI influence must be considefed in both pressurized and gravity drainage well design, although tidal iduence is much more significant in gravity drainage well design. Tide elevations are defined as follows: Mean Lower Low Water (MLLVThe average of the lowest low tide that generally occurs each day Mean Low Wakr QviLW)-The average of all the low tides that generally occur twice each day Mean High Water O-The average of all the high tides that gendyoccur twice each day Mean Higher High Water (MHHW)-The average of the highest high tide that generally occurs each day Nautical Chart 11442 gives tidal informatian for Key West (24' 33'N/81° 48'W) that is summarized in Exhibit 1. This tidal information and Year 2002 tide prediction tables sub- sequently referenced in this technical memorandum (I'M) are on the same datum (MLLW), which, however, is different from the datum for all ground surface elevations in Key West and everywhere. The ground surface datum is the National Geodetic Vertical Datum of 1929 (NGVD1929). men1 Tilnfamakn kr Key West (24'33'N 1 81°48W) Mwn llkrn Moan Higher LowWr Hlgh Water Hlgh Wlbr (MLW) WW) (MHHW) 0.2 1.5 1.8 (Navigation Chert Datum d MUW) Nate: Florida Department of Environmental Protection PEP)data provide two tidal stations that are referend to NGVD 1929 with the same latitude and longitude as that provided in Nautical Chart 11442. Tidal information for these two stations is provided in Exhibit 2 As shown in Exhiit 2,2average adjustment to convert from the Navigation Chart/Tide Prediction Table datum to the NGVD 1929 datum is approximately -0.6 feet. um2 Tidd !Won Irkmakm Mwn Noan M#n Higher LavrW.br High Wabr HIghW-r WLW) (MHW) (MHHW) Key West ldand -0.39 0.92 121 Site # 87WBO LaWude 24" 332N L#lgihrde 81" 48.5W Key West Hawkchamel -0.47 0.97 1.27 Site # 8724557 Letitude 24" 327'N LongUude 81" 47.6W Average of Tide Stations -0.43 0.99 124 Average~Be(wanTieCheR/ -0.63 . 4.56 -056 Tide Prediction Tables and NOVD1929 Nate: ~besedon#CM)1929 Exhibit 3 summarizes Key West tidal information referenced to NGVD 1929 that is used in this TM. Extam3 Tidal I- fa Key West Referenoed to NGVD 1929 [Tzllwn Mean Mom Mnn High Lowwater HlghWatw Hl~hWatw (RIILW) (YHW) (MHHW) Eklwtion -0.4 0.9 1.2 (NGVD 1929) In thie TM,low tide is cansidered to be the Mean Low Water (MLW)elevation of 4.4 NGVD 1929, and high tide is considered to be the Mean Higher High Water 0elevation of 1.2 NGVD 1929. Because high tide is limiting for both pressurized and gravity drainage well capacity, further discmion of the MHHW is provided. Because! MHHW is a mean, tides greater than and less than this mean elevation of 1.2 NGVD 1929 occur throughout the year. Exhibit 4 shows the percent of time the Higher High Water (HHW) ispredicted to be above the MHHW elevation of 1.2 NGVD 1929 in Year 202. -4 Frequency Msblbulion for Year 2002 far Key West HiiHigh Wder Predded Elevakn,(NG\ID 1929 PercentdtineorWumberdDaysinYear Rwrtion (NGVD 1928) 20az Higher High W (HHW) is -tobeEqurlboarG-thn 1 1.3 1.4 1.5 1.6 1.7 1.8 13 20 Elevation M %dTLne 61.4 50.7 40.3 29.6 171 7.4 4.1 22 0.8 Nlm&~d Daye m IS iu ioe ss n is a 3 -Hieher High - Although every month can be expected to have some higher high tides above the mean, September and Wber typically have the highest higher tides. For Year 2002, every day in September and October is predicted to have higher high tides greater than the MHHW elevation 1.2 NGVI) 1929.