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HomeMy WebLinkAboutFDA Guidence of Marinas - EH General - 10/10/2007 FAX TO: Brian McGinnis FROM: Mason County Planning Department Ryan Crater, Land Use Planner/Code Enforcement 411 N. 5th • P.O. Box 279 Shelton, WA 98584 360.427.9670 ext. 577 360.427.8425 fax ryancnco.mason.wa.us DATE: October 10, 2007 PAGES: (15) including cover sheet Comments: Washington State Department of Health 10/05/2007 10:07 FAX 360 236 2257 Shellfish & Water Protec Z 001/015 Office of Shellfish and Water Protection Washington State Department of Post Office Box 47824 ealth Olympia, WA 98504-7824 Phone: (360) 236-3330 FAX: (360) 236-2257 Fax To: Fax Number: ._�� __..__—.-----------.____.- 3 ' -------- From: --- �` �---------Phone: ._ Date: Number of pages: (not Including cover) Note: PUBLIC HEALTH ----_ _.__.__._._.___..------------.---__.------------ ---.___..___ ALWAYS WORKING FOR A $AFIR AWp Phis message may be confidential.If you received it b ke, HIN�N lease notifythe sender and return the item. All messages es Co to an HEALTHIER WAS al from the Department of Health may be disclosed to the public." 10/05/2007 10:08 FAX 360 236 2257 Shellfish & Water Protec Z 002/015 GROWING'AREAS #102 MARINAS FDA Guideline Shellfish Sanitation Branch 200 "C" Street, S.W. (HFF-344) Washington, D.C." 20204 ISH it EVALUATION OF MARINAS BY STATE SHELLF . SANITATION CONTROL OFFICIALS The foilowing.guideline is provided to ensure-the uniform application of thi—National Shellfish Sanitation Program (NSSP) criter is, as adopted by the Interstate Shellfish Sanitation Conference(ISSC),forthe evaluation and classification of shellfish growing waters in and around docks, marinas or other boat mooring areas. RAOItGROUNR A marina policy was developed at the August 1986 ISSC meeting (1). It was recognized that a marina in a shellfish growing area is a potential pollution source,anti that-a closure zone is required to prevent the harvest of shellfish :for human consumption in and ,around occupied marinas. The purpose -of the policy was. to establish-,a uniform national approach to developing marina closures. At the July 1988 ISSC meeting, approval was given to incorporate the marina policy into.the,definition and growingarea classification sections of the NSSP Manual. This policy isnow incorporated;into the 1988-Revision of the NSSP!Manual of Operations- Part I under Section C.9 (2). 132- SANSURVEY - 0994-NETsu 10/05/2007 10:09 FAX 360 236 2257 Shellfish & Water Protec Z 003/015 GROMW AREAS #102 MARINAS GUIDELINE The following definition is from the 1988 revision of the NSSP Manual of Operations: Marina: Any structure including docks, ramps, and floating docks which is utilized for Clocking, storing or otherwise mooring vessels, and usually but not necessarily for providing services to vessels such as repairing, fueling, security, or other related activities. Because every discharge from a marine toilet has the potential to transmit pathogens, every watercraft, (-barge, houseboat, or boat) public:or private,,that can.prodtrce 'a discharge from a marine toilet shall be considered when using this guideline to evaluate shellfish growing waters. In view of the fact that many marina faciFities.are adjacent to sheµfishing areas, and that waste discharges are not uniformly distributed in the water column, detection of low levels of coliforms from waste discharges by current pollution monitoring methods may novprovide suffrclent#reformation toy properly-classify the waters in or adjaoerrt: to a marina. The high public health risk associated with AU discharge of untreated waste, requires that each marina and mooring area closure be considered separately. The State Shellfish Control Authority (SSCA)` will' 'calculate the dilution volume necessary to reduce the theoretically derived wasteload of bacterial indicators to a safe` level, without regard to levels observed by' monitoring. Since marine''toilets provide only limited or no"treatment, abd the environmental exposure time for the discharge is short, human waste discharges from boats contain essentially unattenuated fecal bacteria and viruses. Forthis reason,discharge from marine toilets represent a greater public health risk than other discharges of sanitary waste, and no correlation of health risk with indicator densities observed by baoteriologiical monitoring can be expected. The NSSP Manual states that a classification other than approvedis required for the area within a'marine proper as well as for adjacent waters. This requiremerit is based on�the public health requisite that'waters receiving`waste`discharges from marine toilets are not suitable for the direct harvest of shellfish destined for human consumption. Section C, Paragraph 2.b follows: "b A prohibited area shall be established as a safety zone adjacent to each sewage treatment plant outfall and other waste discharges." (emphasis added) The NSSP Manual (Section C, Paragraph 9.b) also states that a dilution analysis will be used for making marina closure determinations. The number of boats in the marina SANSURVEY - 0994-NETsu 133 10/05/2007 10:10 FAX 360 236 2257 Shellfish & Water Protec U 004/015 GROWING AREAS #102 MARINAS and the number of people on them will determine the potential pollution impact. The per capita discharge of fecal coliforms, coupled with the population in the marina, can be used;to_,estimate a closure zone. Closures for existing or proposed. marinas shall be developed assuming 100% boat slip occupancy; two persons per boat, and a 2 x 10'fecal coliform (FC) contribution per person per day, unless actual,occupancy and discharge rates are documented by surveys conducted for individual marinas on a case by case basis. This documentation shall be maintained as specified .by the NSSP Manual_Part 1, Section C, Paragraph 1 .f, for reevaluation of sanitary survey information. Similarly, any expansion, modification, or change in theoperation of the marina will necessitate the reevaluation of the marina occupancy rate. In determining the-above loading rate§:, a minimum factor should be considered to provide protection against intentional or unintentional waste discharges from boats in the marina. Even if overboard discharges are prohibited, a closure zone is required and the SSCA should stipulate a minimum loading factor of 10 percent li.e,, a minimum marina occupancy .rate). The theoretical waste discharge based on the occupancy and discharge rate, will be considered to be completely mixed in and around the marina. The marina closure zone shall be calculated to reduce.the assumed bacterial load to a FC value of 14 MPN per 100 Ml,. in the volume of, water in the vicinity of the marina. If the. results of hydrographic studies are used, the estimated fecal coliform contribution+ can be distributed throughout the volume of water calculated to flow by the site in 24 hours (3). Harvesting of shellfish for controlled purification or relay shall ngt be permitted from within. the marina proper when boats are,present. If the shoreline.survey, properly assesses the other actual or potential pollution sources, the area of:the marina-closure zone outside of the marina proper may be classified restricted to permit harvesting of shellfish for relaiy. Harvesting of shellfish-for controlled purification shall not be permitted from this.zone, If-boats are root,present in certain seasons (as in some geographical areas) the marina`closure zone may be reclassified to permit-opening to harvest for either direct marketing, controlled purification, or relay; but only if detailed studies have been conducted over sufficient periods of time to verify that the shellfish can purge themselves.and do not present a public health hazard. During such periods the SSCA shall, document that the area,meets the specific NSSP criteria for the classification allowing.harvest, 134 SANSURVEY - 0994-NETSU 10/05/2007 10:12 FAX 360 236 2257 Shellfish & Water Protec IM005/015 GROWING-AREAS #102 MARINAS APPLICATIQN QED tjSSP CRITERIA Factors which shall be considered in assessing the potential impact from,marinas are: 1. Quanti#y of Vjste The use of 2 x 10' for the theoretical fecal coiiform contribution per person per day has been accepted by the ISSC. This value is generally recognized in scientific literature (4). 2. NumbA f_of Peoolg Cgn1ribiging Wgse The quantity of waste potentially originating in a marina depends on the,number of people who.are present in the marina. The fewer Boats that are found. to be.occupied, the smaller the expected impact from the marina will be. The Manual provides for establishing an occupancy rate for each marina..The occupancy rate of the marina shall be documented by actual observation of marina operations. Each marina shall be considered .Separately. Three considerations shall be documented: a. The number of boats with installed toilets in the marina having the capability.to discharge to the environment during the day or night. b. The number of people on board-the boats in the marina. This inventory shall be taken during the expected high usage times,such as weekends and holidays. The inventory shall have continuity so that changes in population during the day or night can be ddcurnented. Regional differences in boat usage and therefore,.the period of high usage will. vary. c. The availability and use of pumpout facilities,at the marina-(5). Without.the above site specific information,the NSSP requires that two persons per boat be used for sizing the closed area around the marina (2). 3., , Dilution Hydrographic studies may be used to determine the water volume available for dilution and Aimits of travel of discharges from a.marina. The area to be closed'shall provide sufficient water volume for calculations to show that theorelical discharges from the,marian are diluted to 14 fecal coliforms.per 100 mL of water (6). In situations where there are no hydrographic studies, the closed area is.to be established on a volumetric basis as though the.wastes area completely mixed and uniformly distributed in and around the marina. The closed area volume is based upon average water depth and shall be sufficient to dilute the assumed wasteload to a value of 14 fecal coliforms per 100 mL. SANSURVEY - 0994-NETSU 135 10/05/2007 10:14 FAX 360 236 2257 Shellfish & Water Protec Q 006/015 GROWING AREAS #102 MARINAS EXAMPLE CALCULATIONS The following examples show how various factors are to be considered in closure area determinations around marinas: se 1: No Documentation of Occupancy or,Discharge Rates_ Number of Boat Slips = 50 Number of People = 2 x 50 = 100 Number of FC = 100 x 2 x 109 200 x 109 200 x 109 FC Dilution Volume Required ------ ' 14 FC x 1000 mL 100 mL liter V = 1.4 x 109 liters (5.0 x 10' cu ft) Average Depth in Vicinity of Marina = 3 meters 00 ft) Closed Area Required = 1.4 x 109 liters 3 meters x 1000 liters cubic meter A = 4.7 x 105 square meters (5.0 x 106 sq ft)- Radius of Half Circle = 2/ (4.7 x 105) Closed Area Ifor example)* R = 550 meters (1800 ft) 'Note:This example of a half circle closure(typical for a marina on a straight shoreline facing open water represents the minimal closure area in an idealized situation. In most states,unless closure buoys are used,a specific point to point closure encompassing a somewhat larger area, would be required so that the Marina elgwre can be:effectively enforced.rced. Aotual volumes of other geometries such as narrow waterways,coves or lagoons should be used to calculate the minimum closure area for each site specific marina closure. 136 SANSURVEY - 0994-NETSU 10/05/2007 10:15 FAX 360 236 2257 Shellfish & Water Protec IM007/015 GROWING.AREAS #102 MARINAS Case 2: Boat Slip Occupancy, Population, Holding Tanks and Pumpout Facilities Documented. Number of Boat Slips = 50 Slip Occupancy - Holiday Weekends = 40 (80%) Boats with No Holding Tanks` = 16 (16/40 - 40%)- Average People Per Boat = 1 .5 Number of People = 1.5 x 40% x 80%x 50 = 24 Number of FC 24 x 2 x 101 = 48 x 10' Dilution Volume = 48 x 109 FC Required 14 FC x 1000 mL 100 mL liter u V = 3.4 x 108' liters 0 .2 x 107 cu#t) Average Depth in Vicinity of Marina = 3 meters 0 0 ft) Closed Area Required = 3.4 x 108 liters 3 meters x 1 000-liters cubic meter A = 1.1 x 106 sq meters (1.2 x 10s sq ft) Radius of Half Circle Closed Area = 2 fir 0 .1 x 105) (for example)" R 265 meters (870 ft) •Punpout facNities coratrtently used. Increase percentage if otherwise. •'See Note for Case 1. SANSLlRVEY - 0994-NETsu 137 10/05/2007 10:15 FAX 360 236 2257 Shellfish & Water Protec Z 008/015 V I R G I N I A S A P P R 0 A C H T O E S T A B L I S H I N G B U F F C R Z 0 N C S f i j, Robert be t C. Croonenberghs, Ph.D. Assistant Director Division of Shellfish� Sanitation Virginia Department of health 10/17/89 10/05/2007 10:16 FAX 360 236 2257 Shellfish & Water Protec U 009/015 VIRGINIA'S APPROACH TO ESTABLISHING BUFFER ZONES INTRODUCTION For years the Virginia Department of Health (VUII) has used rules of thumb and professional judgement, float studies and a healthy dose of conservatism to establish buffer zones around marinas and sewage treatment plants. Recognizing the need to establish these buffer zones on a more scientific basis, the Department began talking with the Virginia Institute of Marine Science (VIMS) about the feasibility of developing modeling capabilities . Mathematical models already existed for rather accurately predicting the transport of pollutants such as bacteria and viruses, but their implementation required the input of site specific data which was quite expensive to obtain, and of no use for deter- mining other buffer zones. Discussion centered abound developing a genera- lized mathematical model that would use physical parameters readily available to "desk top bureaucrats" for predicting the size of needed buffer zones. The work, a user friendly BASIC program, was developed by Dr. John Hamrick and Dr. Bruce Neilsen of VIMS for use on a personal computer. GENERALIZED OESCWIPTION The model is a generalized advection-dispersion model that simulates a steady state condition. Simply put, this means that it predicts an average or constant situation that would occur after numerous tidal cycles. It accounts for the advection of bacteria whirl is. due to tidal movement and freshwater throughput (runoff) and for the dispersion of bacteria due to shear effects and eddies. In comparision to the state-of-the-art in mathematical modeling, it uses a relatively simple mixing and transport model as its basis. The model assumes uniform mixing of the water and bacteria from top to bottom. It also assumes a rectangular channel of a uniform depth and width and a constant mass transport velocity. However, the effects of nonuniform longitudinal velocity are taken into account by a safety factor (ganina) . The model also incorporates a die-off factor for bacteria. This factor is necessary because straight dilution solutions that do not incorporate a die-off factor produce unrealistically large buffer zones. Since the die- off of bacteria does occur in the environment, and since the growing area standard is based on a concentration of bacteria, it is logical to incorporate a die-off factor in the model . HYUROGRAPHIC INPUTS As indicated, a fundamental concept of the model's development was that the input data would be easily obtainable. Sources such as U.S.G.S. topographic maps and NOAA nautical charts can be used to obtain the average channel width and depth, .and the channel. length. The freshwater input to the channel can be obtained from stream gauging stations, or can be calculated using average runoff volumes calculated for the watershed on a unit area basis. The semi- diurnal '(twice. daily} tidal. period is known, and does not vary significantly throughout Virginia. The tidal amplitude is needed and can be obtained from 10/05/2007 10:18 FAX 360 236 2257 Shellfish & Water Protec Z010/015 Page Il NOAA tide tables. Likewise, the maximum tidal velocity is needed, and can often be obtained d;i.rect,ly froln tide tables, otherwise a sim,ple .formula is provided that uses 'the above, data to calculate the velocity. MICROBI LOGIOAL INPUTS Two micrbblologicaI inputs are needed, the number of bacteria added, per unit of time, .J.e. .a rate, and the die-off rate of th.e bact.eria. . For example, the rate of addition of fecal coliforms can be estimated using the average nuotber of fecal col.iforms contributed by a person times the expected number of people for a marina, or concentrations times volumes from sewage treatment plants (STPs), The die-off rate of fecal coliforms is generally accepted to be about 0.7 log-per day for midlatitude estuaries, though this can be affected by temperature and other. factors. SAFETY FACTORS AND PROFESSIONAL JUDGMENT There is a natural tendency when first using a mathematical model to either put too much .trust in the model , or to distrust it altogether. in. using this model , it has been our experience that the model is very precise, providin�j a finite distance for a buffer zone, but to make that answer accurate requires considerable professional judgment . Since the math of the model predicts the average outcome of the physical parameters*. Used; as public:-health officials we must try to account for the rare e-nv:iro.nmental event that may Fuse ir,-_.ceased transport of bacteria , and incorporate that possibility into the size of our buffer zone. in order to provide this added .measure of safety, the model has been designed to predict adverse case scenarios as far as is possible with the math. In addition, one can choose from a range of possible conditions :for certain input ,var.7ables t-o: provide as much publ is hea 1 th 'protection with regard to that physical condition as one wishes. To date VDH uses the following safety factors , and may incorporate more if necessary. 1 . The number of fecal coliforms discharged to the shellfish growing area can be estimated in a conservative manner. -Amounts discharged i"nto marina areas by boats. 'c'an be esti-mated using guidelines as required by the . NSSP_ Amounts `di'scharged by sewage treatment facilities can be based on the upper limits of their NPOES permit limits. 2. The die-off rate of fecal coliforms is affected by a number of factors. While an average die-off rate in estuaries is typically about 0.7 log per day, a 0.5 log per day rate has been shown by microbiologists at VIMS to be a c more onserva 1ve yet realist-ic number for Virginia. In addition, that rate is a- ected by temperature changes, with a higher die-off rate on average occurring with warmer temperatures, so a- conser i erature of 5% will be _used for ear-round STP buffers and 150C For seasona manna buffers: yOther factors that increase the die-off rate such -as sun l ght, sektl j and salinity effects are conservatively not included. 10/05/2007 10:20 FAX 360 236 2257 Shellfish & Water Protec Q011/015 C Page ilI 3. Since the output ' from the computer is in concentration with respect to distance from the discharge :point, one can decide on a case-by-case basis whether to run the buffer -zone to the point where the discharge is expected to be dispersed down to the standard (14 MPN/100ml for example), to where the discharge plus the ambient background concentration meets the standard, or to where the bacteria nearly equal zero. For hospital S.TP discharges, the VDH will establish buffer zones based-on the effluent being dispersed to nearly zero. For most STPs the buffer zone will be drawn where the coricentra- tion of the discharge plus the background meets the standa"rd.' 4 . The freshwater input to the es.tuarine system has a significant effect upon the downstream distance that bacteria are predicted to be transported before their concentration drops to less than the growing area water quality standard. For streams and rivers that have gauging stations, VDH has chosen to use the 15 day high average flow, which roughly corresponds to the annual flood, as the conservative input amount. Tributaries with small drainage basins could be considered to have practically a zero freshwater input, but VDH has obtained per acre runoff factors for the various tidewater areas, and this factor is multiplied times the acreage of Ghe watershed of these creeks to esti- mate the freshwater input to tiie tributary. 5. The model itself is designed to conservatively estimate both the upstrea d across stream rt distanc. achieved by th.e indicator bacteria. his is done by setting the freshwater in,R,�.o`zer — w summer flow durin the' these two d ) In Lf:' _ hypot;. tical situation o � ttle or no freshwater input, there is little or no upstream head to retard the move- ment of bacterid upstream with the tide, and likewise, with little or no fresh- water input, the bacteria tend to stay in .the vicinity of the discharge area longer, and 'so have more of an opportunity to di-s erse across the s t- vardl v ff r o in sh re. is me-tTiod of calculi n. increases t size of the neede buffer zone in both the upstream and -across stream directions. 6. The mathematical model has a gamma factor built into it that modifies the dispersion coefficients. This gamma factor accounts for stream bed irregularities that change shear and edd:ies,. By using this 'factor,' one is led to a result that incorporates the maximum amount of additional dispersion that can occur under -the given set of basic stream bed geometries. This means that since the channel is not a perfect rectangle, this factor provides a worst case condition result (i.e the 16aximurn transport) that can occur for upstream and downstream movement of the bacteria . 1 . Once all 'these factors are determined and input into the 'microcomputer, an answer is generated within a few minutes. One can then turn around and "tweek" the model by changing certain physical parameters to represent extreme environmental- conditions" and thus- see how. the output varies. For example, one can anticipate the effects of stratification of the_'estuary due to temperature or salinity differences- by reducing the depth variable. - One Wright estimate the effects of high winds from a particular direction by adjusting the tidal velocity for 2 to 3 day wind events, or by changing. the mass transport velocity for wind events of a week or more. The point is that all these condi- tions can quickly and easily be tested with the model. Then, the coup de grace 10/05/2007 10:22 FAX 360 236 2257 Shellfish & Water Protec U 012/015 Page IV of conservatism is that one can draw a buffer around the outer limits of these possibilities.- FUTURE USES The VD11 has been 'working with this model for quite some time' to come 'to terms w ith the degree of public health safety that can be reasonably incorporated into this model. Most of these issues have been worked out, but undoubtedly there will be more. Recently Dr. Hamrick developed a new output for the model that indicates the rate of passage of bacteria at any distance downstream from the source. As such, channels with widely varying geometries can easily be subdivided into units of more uniform shape, with the output at the downstream end of the segment being stated in a form that can then be directly used in the math calculation for next section. A good example of this is an instance where a tributary has an STP on it and the mouth of the tributary is predicted to discharge a significant number of. bacteria into a larger river. The computer model now provides the rate of input of bacteria to that larger river, and the tributary can be treated as a point source discharge to the larger river. Dr. Hamrick and Dr. Neilson are interested in refining this model in the future so as to be even more accurate, and hopefully VDii will be able to fund that effort. An .area of study might pertain to better prediction of: the effects of wind. One project of particular interest would be to alter this model from steady state to impulse input so that it can be run for sewage bypass situations , where a large. amount of sewage is discharged in a relatively short time period: 10/05/2007 10:24 FAX 360 236 2257 Shellfish & Water Protec IM013/015 INSTRUCTIONS FOR USING THE COMPUTER MATH MODEL FACILITY WATER BODY GROWING AREA Before utilizing the computer program, the following input values must be determined or calculated: 1. M = 7. Lc = 2. H 8. Lu = 3 qm - 4. U 5 B 6. Kd 1. M = # fecal col iform organisms/sec in the volume discharged (contami- nant loading rate) . A. Sewage Discharges 1 . For raw sewage = 107 FC/100 ml Conversion Factor: 10.5120 FC-hr X (# gallons) gal—sec # hours 2. For 1° sewage = 106 FC/100ml Conversion Factor: 10510 FC -hr X (# gallons) _ ga aec # hours 3. For treated sewage: a . use VPDES permit limits for design flow (Q). and fecal MPN weekly average (usually 400 MPN/100ml ) or, b. if plant exceeds permit limits , use DMR as basis = use high monthly average over past 12 months Conversion: 43 ,808 ml - .day x MGD x M_ - FC/sec sec-MGD B. Marinas FDA FC value per person = 2 x 109 FC/day = 2.3x104 FC/sec 4 2 ��o �C � = where M = 2.3 x 10 1 /e M M N NSFoFm w e P - _� P P N - # people/boat G� NP = # slips or boats Fo = occupancy rate Fm = failure rate- 4 M = 2 .3 x 10 x Np_x Ns x FxF = FC/sec r 10/05/2007 10:24 FAX 360 236 2257 Shellfish & Water Protec lj�014/015 -2- i C. Flux at a section of the stream. j Upstreafi source used as point source further .downstream. Read directly from preliminary run - "X flux in organisms: per second" . Use X/B vafue Corresponding to downstream distance of point where secondary "point" source is located. X/B . X flux 2. H = mean water depth (meters). Obtain depth from USGS or NOAA charts. If depth varies greatly, may determine the average across stream depth at the point of discharge by calculating the mean depth from A _ cross section area average width Cross section area may be estimated by laying out on quadrille paper. Use depth near outfall , if projected closure does not exceed this depth. Since most depth soundings are in feet, convert to meters. 0. 3048 m/ft X ft = m 3. qm = m-aximum ebb current. If available from current tables, con. -f-C knoc, to m/sec. knots x .515 m/sec To calculate q use q = 4al m m H a = the difference between :high and low water: mea-n tide level from tide tables (g.iven in feet) . 0�3048. m/ft x ft = M. LC = length of the creek (tidal portion) in meters from mouth to end of tidal portion H = from #2 above Tt = 44640 seconds q m 4 ( )x 4464U sec)= m/sec 4. U = mass transport velocity, (m/sec) . U = QfT where Q is the net freshwater discharge (m3/sec) and A A is thl cross-sectional area of the stream i Obtain Qf from VWCB information (ft, /sec) . Use h-ighest 15 consecutive days flow and/or VWCB watershed run off factor for the subbasin involved. 10/05/2007 10:26 FAX 360 236 2257 Shellfish & Water Protec Q 015/015 -3- To calculate runoff use planimeter to obtain area of subbasin. Shoreline survey maps are helpful in establishing extent of watershed. sq" x 91 .83 ac/sq" x 1.562x10-3 mi2/ac mi2 mi2 x runoff factor = stream runoff in ft3/sec. ft3/sec x 0.02832 m3/ft3 = m3/se'c Calculate A (width times depth) . See # 2. m2 U = { ) = m/sec U = 0 for across stream values U = 0 or calculated using low summer flows for upstream value 5. B = Stream width in meters = M. 6. Kd. decay rate coefficient ( 'r/sec). Adjust K to water temperature in the stream (from last seawater run for pollution event) . Kd 0. 5/day x (1 . 16x10-5day) Where T = water temperature in °C 20-T) sec) 1 .07 Uu�� use Sou At 5-C , K = 2. 1 X 10-6 d _ r O � 10-C , 3 .0 X 10 6ls 1Z° = 3_S a—�'6S 15' C, 4. 1 X 10A(Marinas) ' ` 2 � X/D �// 5 20-C , 5.8 X 10_6/s ec = O� SD/� LIF( 7. Used in Marina2A: q Ltd /5 0- Lc ` length of short channel from mouth to end of tidal l(9° yy portion. M. � r 8. Used in Marina2A: Lu = upstream length from input point to the closed end. m NOTES: ( 1) Limit of Marina2A determined by Lc-Lu/B. (2) To determine the maximum cross stream distance y for outfalIs located in the middle of a stream, use one half the calculated values for M and B and set U=O. Then assume equal dispersion distances in both directions across the stream from the ou.tfa-11. For midstream discharges, determine the downstream X and upstream -X using one half the calculated values- for M, 8 and U (reduced U for upstream -X) .