[From the U.S. Government Printing Office, www.gpo.gov]

                                                    N171



        HAMPTON HARBOR-
                                RELEASE
                             STUDY
 U-9
   .11"n.                      JUNE 19913


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          567.5
          .1-1136
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                   PUBLIC                  HEALTH
                               prq7- C')




         	 BUREAU OF FOOD PROTECTION
         DIVISION OF PUBLIC HEALTH SERVICES


          HAMPTON HARBOR DYE RELEASE STUDY
                    JUNE 1993



                   CONTRACTOR
             FUGRO MCCLELLAND EAST, INC.
                  PORTSMOUTH, NH


                     SUBITTED TO
               OFFICE OF STATE PLANNING
                  NH COASTAL PROGRAM


                          BY
            PAUL RAICHE AND JOHN SEIFERTH
               FOOD SANITATION SECTION


This report was funded in part by a grant from the Office
of State Planning, NH Coastal Program as authorized by the
National Oceanic and Atmospheric Administratin, award
#NA17070311.

						Publication #93-014






                           HAMPTON HARBOR DYE RELEASE STUDY

                          DIVISION OF PUBLIC HEALTH SERVICES


                       Prepared by Paul Raiche and John Seiferth
                                     
            The objective of this study as stated in the "Proposal For
            Work Task" submitted to the Office of State Planning (0SP)
            on November 12, 1992 basically was twofold. The first
            objective was to determine to what extent a raw or
            partially treated discharge from the Hampton Wasterwater
            Treatment Plant (HWTP) would affect the shellfish beds
            located in Hampton Harbor. Secondly, based upon the report
            DPHS would determine the placement of a closed safety zone
            based upon time of travel of the dye in the harbor.

            The contractor selected for the study was Fugro-McClelland
            (East), Inc. of Portsmouth, New Hampshire.  Their report is
            included as exhibit A.  Figure 7 Of their report
            illustrates the minimum time of travel (time "A") and shows
            that any possible release of a pollutant from the HWTP
            would not reach their stations 6, 7 & 8  in less than one
            tidal cycle (approximately six hours).  Releases at slack
            high tide are considered to be the worst case scenario
            since under any other tidal stage, the "pollutant" would
            not travel as far prior to the tide change.

            Fugro-McClelland concluded that any "pollutant" released
            from HWTP would be diluted 50-100 times by the time, it
            reached the end of Tide Mill Creek.  They then state that
            "at least twice the dilution" as occurred in Tide Mill
            Creek could be expected to occur in Hampton River.  This
            dilution, coupled with a change of tide and some amount of
            die-off, would result in an assumed load of 2 million fecal
            coliforms/100 ml. being diluted to less than 10 fecal
            coliforms/100 ml. at points beyond stations 6, 7 & 8.

            During 1993, DPHS collected water samples in the study area
            in order to determine if there was a correlation between
            observed water quality and the dye release study. The
            number of samples taken was significantly higher than in
            previous years.  Under dry weather conditions, defined as
            less than 1/4 inch rain during the previous two days, the
            samples indicate that there is little pollution found
            downstream of stations 6, 7 & 8.  This agrees with the
            findings of the dye release study.



           Page 2
           Hamton Harbor Dye Release Study
           July 1993

           A shoreline survey was conducted on June 14, 1993 of the
           populated area around Tide Mill Creek and Hampton River.
           The results of that survey found no variations from the
           Hampton Harbor Sanitary Survey Report (Exhibit 2)conducted
           by the Department of Environmental Services (DES) in April
           of 1992.  These surveys show no other significant pollution
           sources other than the treatment plant.  The dye release
           study, therefore, is the dominant factor in determining the
           location of the closed safety zone.

           AS a result of the Fugro-McClelland report all of Tide Mill
           Creek and that portion of Hampton River upstream of
           stations 6, 7 & a should be permanently closed to
           shellfishing.  The report indicates that this area is
           influenced by the HWTP within a six hour time span while
           the rest of the harbor would not be similarly influenced in
           less than 11.5 hours.  Furthermore, any discharge that
           might occur would be diluted to acceptable levels prior to
           reaching those shellfish beds located downstream of the
           proposed closure line.  Figure 1A shows the proposed line
           which would separate the closed safety zone from the open
           areas.   The area north and northwest of that line will be
           included in the closed safety zone.   This includes all of
           Tide Mill Creek, Hampton Falls River and Hampton River.

           A Memorandum of Understanding will have to be developed
           among DPHS, DES and the HWTP.  This MOU will have to
           stipulate the time frame for reporting any upset at the
           plant to the division and the time frame by which the
           harbor must be closed to shellfishing.  The total time from
           the occurrence of the upset to the actual posting of the
           area should not exceed the 11.5 hours referred to in the
           report.   Also, a Memorandumof Understanding is presently
           being formulated between the Office of State Planning, the
           Department of Environmental Services, The Department of
           Health and Human Services and The Department of Fish and
           Game which will delineate the actions to be taken prior to
           July 1, 1994 in order to determine the classification of
           Hampton Harbor





                                                                                                                                                                  rxgaa 0 McClelland
                                                                                         FIGURE 1A







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                                                              PROPOSED LINE OF                        PREPARED FOR THE
                                                           PERMANENT CLOSURE                          NH DEPT. OF PUBLIC                                     FIGURE 1A
                                                           Hampton Harbor Dye                         HEALTH SERVICES,
                                                           Study, Wastewater                          6 HAZEN DRIVE                                      -fijaRa a mccl4flukd
                                       USGS                Effluent Tlme of Travel,                   CONCORD, NH 03301
                                  Hampton, NH              Hampton, NH,                                  May                           Job No.
                                 7.5'Min. Serfes                                                                                       16167999














       ,Was







                                                                                                   GIZU   13
                                                                                                           1 MCCI.elland
                                               EXHIBIT A









                        HAMrTON WASTEWATER TREATMENT FACILITY DYE STUDY



              Objectives:
              The primary objective of this study is to estimate the time of travel for effluent from the
              Hampton wastewater treatment facility to various known shellfish beds in the Hampton River
              and Hampton Harbor, as required by the National She       11fish Sanitation Act. Secondarily, the
              dilution factors associated with travel to these shellfish beds are of interest.

              Approach:
              The study approach has been detailed in the submitted work plan. It           basically consists of
              introducing rhodarnine dye (Intracid Rhodamine WT Liquid) at an elevated concentration to the
              dechlorination tank at the Hampton wastewater treatment facility at high tide and tracing the
              movement of the dye through the ensuing tidal cycle by fluorometric measurement. Stations
              were established at the input point, slightly downstream of the effluent outfall, at three points
              along Tide Mill Creek, and at multiple locations in the Hampton River and Harbor. Once dye
              was detected at a station, a sampling crew monitored the increase in fluorescence level for half an
              hour or until the level stabilized (whichever came first), then moved to the next station
              downstream.     Additional grab samples were collected and fluorometrically tested later as
              warranted by conditions in the system. Of particular note was the change in tide, which moved
              much of the dye back upstream during the second half of the study period. This upstream
              movement was tracked when it became apparent that no further downstream movement would
              occur during the selected tidal cycle.

              For each station sampled, a graph of concentration over time was prepared. From these graphs it
              is possible to estimate the time of travel from the treatment facility outfall to any of the sampled
              stations. A dilution factor range under the tidal conditions of the test has been calculated for
              each station, allowing some prediction of the resultant concentration of a discharged pollutant at
              any. sampled station.
              Results:'
              Dye Input (Stations I & -2J
              Rhodamine dye (Intracid Rhodamine WT Liquid) was introduced into a small mixing chamber
              just after dechlorination. at the wastewater treatment facility. Effluent moves from this point
              directly into the discharge pipe. The outflow dye concentration was to be at least 1000 ppb, held
              as constant as possible 'over a three hour input period.        Actual concentrations leaving the
              dechlorination chamber varied from 2300 to 3100 ppb. Discharge varied substantially during the
              dye input period (5:20 AM to 8:50 AM), largely as a consequence of spanning the period when
              most people wake up and begiry water use. Flows varied from 0.8 to 4.7 cfs, corresponding to
              daily flow levels of 0.8 to 3.1 mgd. Input rate for the dye, which was premixed at 240 million
              ppb, was varied from 25 to 64 ml/min in an effort to achieve outflow concentrations of 2300 to


              Hampton TVasteivater Treatment Facility Dye Study






                                                                                                    GREI D McClelland








              2500 ppb. The     100 ppb level resulted from a combination of low flows (0.8 mgd) at the start of
              the dye input and a minimum dye input rate of 25 ml/min. Once the di@charge began to increase,
              input concentrations were checked and adjusted as necessary in respons'ejo flow measurements
              at the wastewater treatment facility during the dye addition to maintain the most constant effluent
              concentration possible.

              On Thursday, May 27,     1993, the high tide at the treatment facility occurred slightly after 5 AM.
              Dye input commenced      at 5:20 AM at the time of the first noticeable downstream movement of
              water in the receiving tidal channel, and continued for 3.5 hours, spanning a major decrease in
              channel volume in response to the outgoing tide. Monitoring started at the initiation of dye input
              and continued for about nine hours, several hours after it became apparent that no ftu-ther dye
              inputs to the Hampton River would occur during that tidal cycle. Monitoring stations are shown
              in Figure 1. Station I is the discharge (as the effluent enters the discharge pipe from the mixing
              chamber), while station 2 is 100 ft downstream of the discharge point in the tidal creek.

              Background fluorescence was less than 5 units at stations I and 2 prior to dye addition. The
              initial dye concentration in the dechlorination chamber ranged from 1013 to 2215 units, but it
              should be remembered that mixing was not complete until the dye exited the chamber and the
              fluorometer is not designed to accurately read measurements above 500 units. Actual dye
              concentration was maintained at 2300 to 2500 ppb for most of the input period.

              The high water level in the tidal creek during high tide caused surcharging of the outfall pipe and
              substantial dilution of the dye before the effluent was actually discharged into the creek. The
              surcharging also greatly slowed the initial discharge of dye-laden efflluent; it was at least 0.7
              hours before dye reached station 2 at any appreciable concentration (Table 1, Figure 2). Dye was
              clearly visible 0.9 hours after input. For several hours after high tide, while the creek channel
              volume was still high, the dye concentration at station 2 was <100 units, suggesting at least a
              tenfold (and possibly as much as forty-fold) dilution factor at station 2. As the creek volume
              decreased with lowering tide, the travel time of dye in the discharge pipe declined to under 10
              minutes   and the dilution factor decreased drastically.     In the last hour of dye addition the
              concentration at station 2 increased to over 200 units, with a high of 500 units. This suggests a
              minimum dilution factor of 2 to 10 at station 2.


              @Activity at the Rt, 5 1 Bridge (StatioD-3-)
              Fluorescence began to rise at station 3,   the Route 51 bridge, at about 7:30 AM, slightly more
              than 2 hours after dye inp Ut began and over an hour after dye reached station 2 (Table 1, Figure
              3). The rhodamine dye does not become visible until a concentration of about 20 units is
              reached, while background levels were less than 10 units, so there is a visibly undetectable range
              over which the dye concentration increases as the dye front approaches a station. The dye
              became visible at station 3 at about 8:30 AM, about 3 hours after dye addition began, 2 hours



              Hampton Wastewater Treatment Facility Dye Study






                                                                                                      run :03 McClelland




                                                            TABLE 1
                                 RELATIVE FLUORESCENCE (UNITS) OVER TIME AND SPACE
                                     IN THE TIDE MILL CREEK/HAMPTON RIVER SYSTEM
                                                       ON MAY 27, 1993


                      Military Time   Time  (hr)   Station 2   Station 3    Station 4   Station 5    Station 8
                                            0.0
                                            0.1
                              5:30          0.2          2.6
                                            0.3
                                            0.4
                                            0.5          3.8
                                            0.6
                              6:00          0.7
                                            0.8
                                            0.9           47
                                            1.0
                                            1.1
                              6:30          1.2
                                            1.3
                                            1.4
                                            1.5
                                            1.6
                              7:00          1.7            57
                                            1.8
                                            1.9                      5.3
                                            2.0                      5.4
                                            2.1                          6
                              7:30          2.2                          7
                                            2.3                      8.6
                                            2.4                      8.8
                                            2.5                      9.5-
                                            2.6          500          12
                              8:00          2.7                     12.3
                                            2.8          253
                                            2.9          291
                                            3.0          340
                                            3.1                     18.4             5
                              8:30          3.2                     19.6
                                            3.3                     20.9
                                            3.4                       37             8
                                            3.5                       38
                                            3.6                       40
                              9:00          3.7          123                     12.3            5
                                            3.8                                  13.9
                                            3.9                                  14.6
                                            4.0                                  15.8
                                            4.1                                  17.9






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                                                               SITE LOCUS                                          PREPARED FOR THE
                                                                                                                   NH DEPT. OF PUBLIC                                   FIGURE 1
                                                               Hampton Harbor Dye                                  HEALTH SERVICES,
                                                               Study, Wastewater                                   6 HAZEN DRIVE                                      -r.Ra 0 McClahrld
                                          USGS                 Effluent Time of Travel,                            CONCORD, NH 03301
                                                                                                                                                                    11,-     -
                                    Hampton, NH                Hampton, NH
                                                                                                                   May                           job No
                                   7.5*Mln. Series                                                                 -1993                         616799'9





                                                                                                      .!@Ru -01 McClelland



                      Military Time    Time  (hr)  Station 2    Station 3    Station 4   Station 5    Station 8
                                9:30         4.2          5.8                     20.6
                                             4.3                                  21.8          12
                                             4.4                                  24.7
                                             4.5                                  27.7
                                             4.6                                  29.1
                              10:00          4.7          2.8                     29-.7
                                             4.8                                  30.4
                                             4.9                        30        30.4
                                             5.0                                  28.9         23.4         9.5
                                             5.1
                              10:30          5.2                                                            9.5,
                                             5.3
                                             5.4
                                             5.5
                                             5.6
                              11:00          5.7
                                             5.8
                                             5.9
                                             6.0
                                             6.1
                              11:30          6.2                                               27.2
                                             6.3
                                             6.4                                  28.5
                                             6.5                        12                     10. 14
                                             6.6                                                            7.6
                              12:00          6.7                                     29         5.5
                                             6.8
                                             6.9
                                             7.0
                                             7.1
                              12:30          7.2                      25.3
                                             7.3                                  11.7
                                             7.4                                                2.4
                                             7.5
                                             7.6
                              13:00          7.7            11
                                             7.8
                                             7.9                        36
                                             8.0                                    8.2
                                             8.1                                                6.6
                                             8.2
                              13:30          8.3
                                             8.4
                                             8.5
                                             8.6
                                             8.7
                              14:001         8.8 1                       10
                                             8.91



                                                                                                                            loot







                                                          FIGURE 2


                                            FLUORESCENCE OF RHODAMINE DYE AT STATION 2



                no


                180


                160

             Uj 140

             z
             LU 120
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             cn                                                                 End of
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             cc 100                                                           Dye Input
             0
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             w                                                                      Tide
             >   60                                                               Change


             Uj  40
             cc

                 20

                                                          1 1 1!111 liji! Eiji !1! 11 !1! !1! 11111111111111 '111!!!! 1 11-H
                   0     H H-i-11 ii ii i i F i i i i ii I H I                                           I
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                                           V@ c@ c@     cli cli c@ 4 4 4 LD* 6 Ln,                        r-@ c6 00* c6
                                                       HOURS FROM START OF DYE INPUT




                                                                                                                              1931







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                                                            FIGURE 3


                                           FLUORESCENCE OF RHODAMINE DYE AT STATION 3





                 45


                 40

               Uj 35

               z
               LU 30
               L)
               U)                                                             End of
               cc 25                                                        Dye Input
               0
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                 15                                                             Change


               LU 10
               cc


                   5
                   0                                         i i i Hi ii i          rHH11!HHHHH       Hiiiiiiiiiii
                           (c) M 04 Lr) M        r- M M w m N U@ O@          @d: r@ (0 CV) CD M CN Ln 00 - Itt r@
                       C5 6 6             c@ c@        c@ c@ c@ 4   4 4   Ln Lo Lo                    r@  C6 06 C6
                                                      HOURS FROM START OF DYE INPUT




                                                                                                                         L9 3j
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                                                                                                             _0 McClelland








               after the dye reached station 2, and an hour after the first evidence of fluorescence increase at
               station 3. Fluorescence rose quickly, peaking at 40 units shortly be-fore 9:00 AM.

               Although only visual examination was performed for the next hour or so (the fluorometer was
               moved to station 4 and the visibility of the dye precluded the need for sampling), dye
               concentrations appeared fairly stable for the next 1.5 hours. A value of 30 units was recorded at
               10: 12 AM, after which there was a decline in fluorescence to 12 units by 11:48 AM. The trailing
               end of the visible dye pulse seemed to pass station 3 about 3 hours after the leading edge reached
               that station. The elapsed time between the first apparent indication of a fluorescence increase
               and the minimum value detected after the peak was about 4.5 hours, about an hour longer than
               the duration of dye addition. There is theref6re considerable dispersion in the upstream and
               downstream directions over the approximately 3000 ft between stations 2 and 3.

               Based on the peak value of 40 fluorescence units at station 3, the dilution factor at this point is 20
               to 40 relative to the initial concentration estimate and 1.2 to 12 relative to the fluorescence at
               station 2. The small tidal channel into which the effluent is discharged meets the main branch of
               Tide Mill Creek slightly upstream of station 3, so dilution at the high end of this estimated range
               is likely.

               Low tide occurred at about 11:00 AM in the Tide Mill          Creek system, and distinct upstream
               movement was discernible between 11:30 AM and noon. A fluorescence value of 25.3 units was
               recorded at 12:30 PM at station 3, indicating that the dye pulse was being moved back upstream
               at that time. A value of I I units was r6corded at station 2 at 1:00 PM, suggesting that only a
               small portion of the dye was traveling up the tidal creek from which it came. The remainder of
               the dye passed upstream in the main branch of Tide Mill Creek; dye was visible upstream of the
               confluence with the tidal channel into which the dye-laden effluent was originally discharged.
               At 2:00 PM the fluorescence at station 3 was 10 units, indicating substantial dilution of any dye
               yet to move upstream of that station.        Elapsed time from the directional change in water
               movement was about two hours. Although a portion of the dye pulse remained intact and was
               pushed upstream, the incoming saltwater appears to provide considerable dilution of the dye
               plume ( .up to fourfold at station 3), based on comparison of peak fluorescence values for
               outgoing and incoming tides.

               Activity in lower Tide Mill Creek (Stations 4 &5@
               Dye appeared to reach station 4 at 9:00 AM, and the concentration rose steadily until about 10:00
               AM and peaked at 30 units (Table 1, Figure 4). Travel time to this station from the input point
               was about 3.7 hours and the travel time from station 2     was about 3 hours. Only slight dilution
               since station 3 is indicated (peak of 40 vs. peak of 30 units). The fluorescence at station 4
               remained stable for over 2 hourp, spanning the period of low tide and reversal in the direction of
               water movement. The fluorescence began to decline between noon and 12:30 PM, reaching 11.7
               units at 12:36 PM and 8.2 units (background level for the Hampton River) at 1:18 PM. The dye


               I-Iatnpton Wasteivater Treatinent Facility Dye Study














                                                                                FIGURE 4


                                                           FLUORESCENCE OF RHODAMINE DYE AT STATION 4



                        50


                        45

                        ;@b
                    D   35
                    LU
                    0
                    z
                    uj  30
                    U                                  End of
                    cn
                    LU
                    cc  25                           Dye Input
                    0
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                    LU                                                                                          Tide
                    >   15                                                                                   Change


                    LU  10
                    cr-

                          5


                                                                                                                                                    i i i i ++-i
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                                                          c@ c@ C-@        c@ C6 c-;    (4 -4    4 U@     U@  Lo'                            r, c6 m m
                                                                          HOURS FROM START OF DYE INPUT











                                                                                                                                                                      CL





                                                                                                  "a -4 McClelland






            pulse never completely passed station 4; the lowest values represent the same water mass moving
            first downstream and then upstream past this station.

            Station 5 exhibited the first signs of fluorescence increase at 9:36 AM, although the first visible
            range reading occurred at 10:18 AM (Table 1, Figure 5). This represents a travel time from
            station I of 4.3 to 5 hours, and a travel time of 3.6 to 4.3 hours from station 2. Beginning at
            10:!18 AM, fluorescence levels remained fairly stable at 23 to 27 units for 1.2 hours, after which
            there was a rapid decline coinciding with the change in tide. Readings were in the background
            range by noon, an hour after low tide and only a few minutes after discernible upstream water
            movement occurred. The water mass containing the dye piled up on itself and was pushed back
            upstream; this process was observable to the naked eye, as dye levels were still in the visible
            range at this point. Fluorescence remained at the background level for the remainder of the
            observation period.

            Dilution at station 5, the last station before entry into the Hampton River, is on the order of 50 to
            100 relative to the initial input level. Dilution since station 2 is by a factor of about 10 to 15.
            There is additional dilution at the leading and trailing ends of the dye plume during the initial
            outgoing tide, and even more substantial dilution of a larger portion of the plume with the
            incoming tide. Some portion of the dye plume remained intact throughout the study period,
            however, and simply moved up and down Tide Mill Creek. The bulk of the dye plume spanned
            stations 4 and 5 when the tide changed, and was pushed upstream beyond station 3 by 2:00 PM
            (high tide occurred after 4:00 PM).

            Activity in the Hampton River
            For about 1.5 hours around low tide, dye-laden water was      able to pass ifito the Hampton River
            from Tide Mill Creek. Water velocities were slow at this point, so the actual volume of water
            leaving the creek and entering the river appeared low. It is roughly estimated that less than 10%
            of the total dye load exited Tide Mill Creek before the tide changed. Nevertheless, a visible
            plume was observed along the northern shoreline for about 200 ft from the confluence of the
            creek and river. The changing tide appears to have caused the dye to hug the shoreline; the
            trajector@y of the dye plume at other tide stages is uncertain.

            Fluorescence levels at station 8, the closest downstream station in the Hampton River, were
            never above 10 units and showed no influence from the dye. Station 8 is part of a three station
            transect over 500 ft upstream of the closest shellfish beds of interest in this study (Figure 1).
            There was no evidence of dye reaching these beds during the study period (Table 1, Figure 6).
            Dy "e that did enter the Hampton River from Tide Mill Creek was rapidly diluted to background
            levels and moved upstream with the incoming tide. As the tide changed, the short dye plume in
            the river dissipated and no dye    I  Id be detected either by eye or with the fluorometer. The
                                               cou
            volume of water moving with the incoming tide simply overwhelmed the small volume of the
            remnant dye plume, diluting it to background levels. It was windy during the study period,


            Hampton Wastevvater Treatment Facility Dye Study














                                                             FIGURE 5


                                              FLUORESCENCE OF RHODAMINE DYE AT STATION 5



                  50


                  45


                  40


                D
                w 35

                z
                Lu 30
                U
                (n                                       End of
                w
                cc 25                                  Dye Input
                0                                                                                 Tide
                  20                                                                            Chan e
                L
                w
                > 15

                  10


                    5
                                                                                   H H H  @-i I-H HlF++-H-Hll-H 1 1111-1 --- f-l ii I
                    0                                                  1-+-++-++H--H-@ H H
                     0 M 0 M N 0 M                 r, M M (0 M N M M                 r, 0  M (00) N'Lo co@,;t r-
                         6 6 6               cli c@ c@    m C-i vi 4 4 "r L6 L@ U')'        co        r@ r@ r@ c6 c6 c6
                                                         HOURS FROM START OF DYE INPUT
                                                                                              L @ha n

                                                                                                                               126













                                                           FIGURE 6

                                             FLUORESCENCE OF@ RHODAMINE DYE AT STATION 8


                  50


                  45


                  40
               D  35
               LU
               0
               z
               Lu 30                                     End of

                                                       Dye input
               cc 25
               0

                  20
               U-                                                                    Tide
               ul                                                                  Change
               >  15


               LU 10
               cc




                    0

                                                                                                 m CN m W
                                         c@       r-                                             co        N 00  00  C6
                                                         C@i vi C'i 14 4 4      Lo' M, W, (6 (6
                                                        HOURS FROM START OF DYE INPUT
                                                                                                                              cl








                                                                                                                              ir

                                                                                                                              CL






                                                       ... . ..... ..... ......... . . ... .



                                                                                                            r."a _01 McClelland








                    which may have aided this mixing process, but the currents created by the change in tide
                    appeared sufficient to create great mixing potential even on the calm" @st of days.

                    Discussion:
                    Travel Time
                    Based on the results of the dye test conducted on May 27, 1993, pollutants discharged from the
                    Hampton wastewater treatment facility reach the Hampton River in no less than 4.3 hours, and
                    do not reach any significant shellfish beds during tl@e first tidal cycle after discharge. As dye was
                    not actually discharged into the tidal creek until between one half and one hour after high tide
                    due to surcharging of the discharge pipe, it is possible to envision a worst case scenario in which
                    a pulse of dye (or other pollutant) released into the receiving tidal channel at exactly high tide
                    might reach the upstream end of the closest shellfish beds just before the tide changes, pushing
                    the dye (or pollutant) upstream and diluting it extensively. At an absolute minimum, therefore,
                    the time of travel from the wastewater facility outfall to the closest shellfish bed is at least 6
                    hours under the test conditions. Minimum times of travel for the lead edge of the dye plume and
                    the visible portion of the plume to selected stations are depicted in Figure 7.

                    The test conditions included a fairly average tidal cycle; lower lows and higher highs are known
                    for Tide Mill Creek. Weather conditions were dry. Had conditions been different, it is not
                    cer-tain that time of travel would have been affected. Additional water at high tide would have
                    resulted in flooding of the non-channel portions of the saltmarsh, possibly impounding portions
                    of the dye plume and slowing complete flushing by several tidal cycles.                 However, the
                    channelized portion of the dye plume would have been subject tcr'roughly the same velocities,
                    leading to similar estimates of minimum travel time. Had the tide been lower, it is conceivable
                    that the dye might have moved into the lower reaches of Tide Mill Creek somewhat more
                    rapidly, but channel configuration suggests that maximum velocities were rapidly achieved under
                    the test conditions.


                    For all but an instantaneous discharge at high tide, the travel time to the closest shellfish beds
                    and into'the harbor-beyond is well over one tidal cycle (approximately 11.5 hours). Discharged
                    pollutants will move upstream and downstream in the Tide Mill Creek system, with each tide
                    change causing further dilution and distribution throughout the associated channels in the
                    saltmarsh. A small portion of the pollutant load would enter the Hampton River each tidal cycle.
                   'The longer the duration of discharge, th@ more tidal cycles it will take for the pollutant to be
                    completely flushed out of the Tide Mill Creek system.

                    Pollutant Concentrations and Dilution Factors
                    During the first tidal cycle aifter an input occurs, that input will be subject to a dilution factor  of
                    50 to 100 in the Tide Mill Creek system and undetermined but substantially greater dilution            in
                    the Hampton River. Insufficient data exists to evaluate dilution in the Hampton River, but it
                    would be expected to be at least twice the dilution experienced in the Tide Mill Creek system,


                    Hampton 11'astewatei, Treatment Facility Dye Study






                                                                                                                                   npu U McClelland










                                                                                                  X
                    Minimum Time olTr3vel to Station                                                                          00              X-
                       from Input Point for:
                                                                                               to
                    A) Leading edge of dye plume
                        (measured as any increase in fluorescence)                                                 3
                                                                                                                                    Cree
                                                                                                 -T                    7-
                    B) Stable concentration of dye
                        (measured as end of sharp increase in fluorescence)


                                                                                                                              ot
                                      A) 0.7 hr
                                      B) 0.9 hr
                                                                                                                                                U
                                        Extreme tidal volurne                                        Cr
                                        change caused further
                                        increases after this time;
                                        also note that travel time                                                            3
                                        declines at lower tide stage                                                          -


                                                                                                                 7            7
                                      A) 2.2 hr
                                      B) 3.4 hr
                                                                                                                       2

                                      A) 3.7 hr                                                                    9   110    11
                                                                                                                   0
                                                                                                                         0
                                      B) 4.5 hr                                                                               0
                                                                                                                              W@


                                                                                                                 12
                                                                                                                                             T E
                                      A) 4.3 hr
                                      13) 5.0 hr                                                     4                        13 Pt
                                                                                                      PC     A4. 7n p I o 7L
                                                                                                                              66dg,  20
                                                                                                             ..140
                                                                                                            -.       ....  :@-
                                                                                                               H
                                      A) 5.5 hr                                                                               15
                                      13) 6.0 hr                                                                              0
                                                                                                10- qs
                                                                                                       1'.. Gilts
                                                                                                                                          .
                                                                                                                                          k
                                                                                                                                          k
                                                                                                                                          k
                    Time "A" represeflfs the first possible appearance of dye                                                 0
                                                                                                                     b
                    no rriatter how dilute, at the station indicated.                            juid                                           Th
                                                                                                               Pt                               Ac
                    Time "B" represents the leveling off point for fluorescence,                                                          .-'.'Seab;
                                                                                                                              T
                    indicating the arrivel of the main body of the dye plume.


                                                                               PREPARED FOR THE
                                          Travel Time                          NH DEPT. OF PUBLIC                             FIGURE 7
                                          Hampton Harbor Dye                   HEALTH SERVICES,
                                          Study, Wastewater                    6 HAZEN DRIVE                                  fur.Ru a mccwbm
                          USGS            Effluent TIme of Travel,             CONCORD, NH 03301
                     Hamptol), NH         Hampton, NH                           June
                                                                                                          ob No.
                    7.5 MIn. Serles                                              1993                    16167999





                                                                                                     rsan IU McClelland

                                                                                                           ..... ......

                                                                                                                     V A,@. C. IAI








              based on a rough estimate of the volume of water between the Tide      Mill Creek inlet and the first
              shellfish beds of interest. Given travel times longer than a tidal cycle, this dilution factor would
              increase. At a minimum, however, it would be reasonable to expect that any pollutant reaching
              the shellfish beds from the wastewater treatment facility! would be subjeci, to a dilution factor of
              10,000 to 20,000 (50 to 100 X 200).

              Subsequent to the initial tidal cycle associated with dye or pollutant input, every tidal cycle
              required to transport a given water mass or pollutant load to the shellfish beds would provide a
              dilution factor of about 10 at the mouth of Tide Mill Cr eek. A larger but unknown dilution factor
              would apply at the closest shellfish bed in the Hampton River. For the dye released in this study,
              it is estimated that at least 10 tidal cycles would be needed to flush all the dye out of Tide Mill
              Creek. Given a peak fluorescence of 27 units in the first flush, fluorescence would be expected
              to decline to the background level (5 to 10 units) after only a few tidal cycles. Based on results
              at station 3, the length of the visible dye plume was cut by at least half by the incoming tide;
              there was no major increase in concentration within the remaining portion of the visible plume,
              so it appears that dilution forces were responsible for the observed change. This further supports
              the hypothesis that dilution to background levels might be reasonably expected within several
              tidal cycles.

              Beyond a single tidal cycle, dye inputs of the magnitude used in this study would not be
              detectable in the main body of Hampton Harbor. As it clearly takes more than one tidal cycle for
              most of a given input to reach the harbor, further transport studies will require dye input at points
              downstream from the Hampton wastewater treatment facility.               Placement of dye at the
              confluence of Tide Mill Creek and the Hampton River at high tide would be the logical next step
              in further evaluation of travel time to significant shellfish beds and relat@d dilution factors.

              For a continuous discharge such as that of the Hampton wastewater treatment facility, the
              concentration of pollutants normally foun@ in the effluent (nutrients, BOD, etc.) should acquire a
              predictable periodicity at any point in the Tide Mill Creek system, with tide stage as the primary
              determinant of pollutant concentration. Additional variability would be introduced by changes in
              dischar& volume, treatment efficiency, tidal height and removal processes in the tidal system.

              With only a change in tidal stage, concentrations would be expected to rise with an outgoing tide
              and fall with an incoming tide. Concentrations within the path through the saltmarsh to the
              mouth of Tide Mill Creek would be expected to be the highest ones encountered, but
              concentrations of any normally discharged pollutant (e.g., nitrogen, phosphorus, suspended
              solids) would be above pre-discharge background levels throughout the Tide Mill Creek system
              as a consequence of tidal movements over multiple cycles.
              Variabilily in discharge volur6, treatment efficiency and removal on non-conservative
              substances (e.g., nutrients) in the marsh system will affect ambient concentrations. The greatest


              Hampton Wastewater Treatment Facility Dye Study






                                                                                                 CaRn A McClelland








          potential influence in this regard is wet weather and storm tides, which have several possible
          effects. Due to infiltration by stormwater runoff and the possibility of major inflows during
          coastal flooding near sewer line manholes, discharge volume may rfse- considerably and
          treatment efficiency will decline during major storms. Flooding of the mar-shes may enhance
          uptake potential for contaminants such as nutrients and increase deleterious exposure for toxic
          substance swhich might be discharged. Given the sources of dilution water (rain and the ocean),
          however, the net effect is likely to be an increase in dilution factor for contaminants leaving the
          Tide Mill Creek system. The exception might be contaminants not normally found in the
          discharge; flooding of industrial/commercial areas and subsequent drainage into the sanitary
          sewer line might cause such a phenomenon. Minimization of infiltration/inflow situations is
          therefore desirable.


          One of the forces governing dilution of inputs is dispersion. Without appreciable active mixing,
          diffusion, channel friction and related forces are expected to lengthen the plume associated with
          any input over its time of travel through the system. It appears as though the length of the
          measurable dye plume increased from the original input duration of 3.5 hours to over 4 hours at
          Station 3. Reversal of flows with the change in tide precludes empirical evaluation of the length
          of the dye plume further downstream, but the observed increase over just the first 200 ft of travel
          distance suggests that dis persion is significant.

          An Evaluation Framewor
          Based on the conducted study, it is not possible to conclusively evaluate the passage of dye or
          other contaminants throughout Hampton Harbor. The failure of the dye to travel to even the first
          shellfish beds is an important finding, however. The minimum time of-travel to the closest
          shellfish beds ;,@ estimated at 6 hours, with little likelihood of that travel time being realized for
          anything other than a "perfectly" timed discharge. A travel time of more than 11.5 hours is
          expected for most inputs, with up to 10 tidal cycles (115 hours) estimated to be necessary to
          completely flush an episodic input from the Tide Mill Creek system. However, inputs may be
          diluted to non-detectable levels within three tidal cycles.

          In terms'of evaluating pollutant concentration scenarios, one would compare a target level for a
          contaminant of interest (e.g., fecal coliform. bacteria at 14/@00 ml) at the closest shellfish beds
          with a measured or predicted concentration in the- wastewater treatment facility discharge,
          modified by dilution, uptake, die-off or other mitigating        processes over the travel time as
          suggested by the results of the dye test. Assuming no die7off or other removal of bacteria and a
          load.of 2 million fecal coliformJ100 ml at exactly high tide, some portion of this load might
          possibly reach the shellfish beds in 6 hours,1having been diluted by at least a factor of 10,000.
          This would result in a delivered concentration of 200 fecal colifon-n/ 100 ml, well in excess of the
          standard for shellfish harvest areas, I More likely, however, would be a travel time of at least 11.5
          hours with a dilution factor of 200,000 and some amount of die-off-, this suggests a delivery
          concentration of less than 10 fecal coliforn-J100 ml, less than the standard.


          Hampton lVastewater Treatment Facility Dye Study





                                                                                             -fiurauu -4 McCle   Hand








              The weakest part of this analysis is the travel time and dilution associated with movement in the
              Hampton River, as the dye barely reached this point during the test pe@fiod. Additional testing,
              beginning with addition at the mouth of Tide Mill Creek at high tide, would be necessary to more
              adequately characterize movement and dilution between that point and shellfish beds of interest.
              Yet with the information gained through the completed dye study, it is apparent that inputs from
              the treatment facility are subject to extended travel times and elevated dilution factors which
              minimize the risk associated with short duration inputs of a potentially deleterious nature.





































              Hampton Wasteivater Treatment Facility Dye Study






                             US Department of Commerce
                             IqOAA Coastal Services Center Library
                             2234 South Hobson Avenue
                             Charleston, SC 29405-2413



























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