FLUSHING STUDY OF THE TIDE MILL CREEK AND HAMPTON RIVER ESTUARIES JUNE 1975 U. S. Environmental Protection Agency Surveillance & Analysis Division Surveillance Branch Technical Studies Section ------- FLUSHII G STUDY OF THE TIDE EtLL CREEK AND HANPTON RIVER ESTUARIES Introduction The New Hampshire 1 dater Supply and Pollution Control Co ission (NHWSPCC) in conjunction with other state and federal agencies are determining the shellfish closure areas for Hampton Harbor. Of particular interest is the flushing time and dispersion of the Hampton Uaste .iater Treatment Plant ( R4TP) discharge to a tributary to Tide Mill Creek. Therefore, the NEWSPCC requested the Envirorunental Protection gency to conduct a flushing rate and dispersion study of the discharge. Study Area Tide Mill Creek drains a tidal marsh of approximately 436 acres. The marsh is divided by the Hampton Beach Expressway with the major drainage area north of the road. The marsh north of the road is characterized by a major channel that meanders through the marsh and a number of minor channels radiating into the marsh area. The area south of the expressway is drained by a number of short channels and ditches running into Tide Mill Creek. Tide Mill Creek subsequently drains into the Hampton River 1950 meters (6400 feet) upstream from the outlet of Hampton Harbor. The Hampton River Estuary can be divided into two sections, the first upstream from the confluence with the Tide Mill Creek d the second downstream from this point. The upstream area drains a tidal marsh and has a number of tributaries that enter into the river. The downstream section flous into Hampton Harbor and is bounded by a small marsh area to the northeast and a larger marsh to the southwest. The downstream section of Hampton River also ------- 2 has large areas of mud flats that uncover at low tide adjacent to the marsh areas mentioned. Procedure The methodolo used to determine the effects of the flushing time and dispersion of the Hampton 1WTP discharge was visual arid fluorometric detec- tion of Rhodamine JT dye. The dye was injected into the study area at the chlorine contact chamber of the Hampton WWT?.. The outfall from the Hampton Treatment Plant is located in a secondary channel in the marsh area at map reference (19.5, A.5). The initial injection of dye was made at a low slack tide on June 3 at 1315 hours. The dye penetrated the main channel of Tide 1 Ltll Creek and the leading edge of the dye was at a point approximately 200 meters (700 feet) upstream of the Expressway Bridge before the inconing tide reversed the direction of flow in the creek. This occured approximately 1.25 hours (141 +5 hours) after the injection was made. High Tide observations of the dye patch indicated high concentrations of the dye remained in the secondary channel from above the W TP discharge to its confluence with Tide Mill Creek and in the adjacent drainage ditches. Dye was also located in Tide 1 1iU Creek upstream from the confluence with the secondary channel, although this dye was not as intense in color as that located in the secondary channel. A second injection was made at the plant approximately 19 hours later (O 0o hrs.) on June If at high slack tide. This injection was monitored during the ebb tide and the position of the dye patch was determined at low slack tide (1400 hrs.). The leading edge of the dye was located adjacent to the marina in the.Hainpton River (map reference (17,Q)). The highest concentration of dye was ------- 3 located in the Hampton River hugging the eastern shore in the area near the Willows (map reference 14,L to 17,?)). The Hampton River in this area is very shallow with depths ranging from 0.150.6 meters (0.5-2. feet). The dye in this area was of fairly uniform concentration throughout. No indication of dye was found west of the Hampton, Hampton Falls town line The peak concentration of the dye in Tide Mill Creek was located at the mouth of the creek. Intensity of the dye in Tide Mill Creek decreased uniformly from the mouth upstream to the expressway bridge. A plot of these data Is provided on Figure 1. The center of mass of the dye cloud was 2700 meters (8900 feet) down stream from the treatment plant and 1450 meters (4700 feet) upstream from the harbor bridge. The dye was again monitored at high slack tide (2030 hrs.). The area between the marina and the mouth of Tide Mill Creek, the adjacent marsh and the Hampton River upstream from the confluence with Tide Mill Creek did not have any de- tectable levels of dye. Dye was detected in Tide Mill Creek with increasing concentration moving upstream into the marsh north of the expressway. Figure 2 presents a plot of these data. Observation of the dye continued at low slack tide, June 5 at 0245 hours. At this time, the peak dye concentration was located approximately 350 meters (1100 feet) upstream from the mouth of the Tide Mill Creek at Blind Creek (map reference (14,1)). The leading edge was 750 meters (2500 feet) upstream from the Harbor bridge. Figure 3 provides a plot of these data. The dye was monitored again at the next high slack tide (0850 hrs.). Detectable levels of dye were not found in the Hampton River. High levels of dye were again present north of the expressway bridge. A third inject1u2 was made in the Hampton River at the mouth of Tide Mill Creek at high tide. This inject .on flushed out of the Harbor ------- -4-. completely leaving residual amounts of dye between the marina and the Willows. The residual dye was checked at hlgh tide (1500 hrs.) to determine any longi- \tudinal movement. Detection at this time indicated little longitudinal move- ment, the dye had been fairly evenly dispersed across the river. Conclusions 1. A positive flow exists in the channel the Hampton fl JTP discharges into for about 1.25 hours after low tide in Hampton Harbor. 2. Waste from the Hampton WTP is not completely transported out of the marsh and Tide Mill Creek during an ebb tide. 3. Material transported to the Hampton River is concentrated along the northeast shore of the river. 4. Complete flushing of the Hampton River exists south of Tide Mill Creek during an ebb tide. ------- LL ,, \ / S wwψ - _ _1 ηJ j t 2 a ii TI _. % t ,t ______ = ii -ij= iii 1T L i i..,- /1\ : ; : η r 4 r. \ I t f . 111 L -t . . ..jl 1 7/ / / 1 η - :- T J $ i . J. . __________________ i 7 I h \ !I! t / I I jI 4 r ri .1 -j LELifA ±iiL L ; J1iLJ T i t I p t- t - - - - -I ;. .: F ::J !\ , D I; T. ________________________ I I I I L ; __ - - - - !- Hampton Heath 1 - . 41 c / -. i--i ! /. I ____ _____ - t I __ __________ T - b z - r 1T I 1 : to 1 IH J - a - - - OC I ...2 - 5 1 t41t 1 lLl t. ; {z J_ - - 1- \ - 1 - T } .Creiek j_2_ _LLic _L_ L 1bo ft 77 i tr \ \,j /_ i i1::: 1 L I !t. _______ ___________________ 1 m r t 1 . 1Lowe;G j f:__________ 11 t 4 : H , ! r zHrt; P 1w_ C - L: . S ibi (jukf C] 1) O T LII - I I - -. I I I ;f ; I. I I I M 4 _. e_____ -- --- i .j- _ .--4,--m - - 11 t - i r E T ? TII ; i ILL J ;s i 1 f_Lii _ L_ _L 1 L __ ± L - I I-i: 1 :t ±_ ____,_ LL - - ::- 4 - -: i - £ - B ck s - , )s ar d /;;. - - I - L - ! istand I i r P - - i I iv w I ..,_ c..1 -..: X 1 ------- 100 90 80 70 60 50 140 30 20 10 0 1L u 1 2 3 14 7 8 9 10 11 12 13 lle 15 16 I FEET IN ThOUSANDS I MOUTH OF TIDE MILL CREEK HARBOR INLET DYE CONCENTRATION V . DISTANCE HAMPION WWTP FIGURE .2 ------- 100 90 8o 70 60 50 140 30 20 10 A 0 I 4i i I 0 1 2 3 / 4 6 7 8 9 1& 11 12 13 14 15 / m mous r s MOUTH OF WWTP CHANNEL MOUTH OF TIDE MILL CREEK D E CONCENTRATION VS DISTANCE T BOR INLET 1 IGURE ------- 8 9 10 0 & 4 ___ ThOUSANDS \ MOUTh OF T E LL EEK DYE CONCENTRATION VS. DISTANCE HAMPTON WTP I , 100 90 80 70 60 50 140 30 20 10 A I I I I U. 12 131 12. 15 HARBOR INLET I 16 ------- |