Flushing Study of the Tide Mill Creek and Hampton River Estuaries.


          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

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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

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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

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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 0.15—0.6 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

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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.

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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

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100
90
8o
70
60
50
140
30
20
10 A
0 I 4’i 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

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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

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