The URL can be used to link to this page

Home My WebLink AboutNC0026611_Report_19900416NPDES DOCIMENT :SCANNING COVER SHEET Permit: NC0026611 Morehead City WWTP NPDES Document Type: Permit Issuance Wasteload Allocation Authorization to Construct (AtC) Permit Modification Complete File - Historical Engineering Alternatives (EAA) Report Instream Assessment (67b) Speculative Limits Environmental Assessment (EA) Document Date: April 16, 1990. This document ifs printed on reuse paper - igizore any content on the reirerge Elide State of North Carolina Department of Environment, Health, and Natural Resources Division of Environmental Management 512 North Salisbury Street • Raleigh, North Carolina 27611 James G. Martin, Govemor George T. Everett, Ph.D. William W. Cobey, Jr., Secretary April 16, 1990 Mr. Tyndall Lewis McDavid Associates, Inc. 109 East Walnut Street P.O. Box 1776 Goldsboro, NC 27533 Subject: Calico Creek Modeling Results Morehead City WWTP - NPDES No. NC0026611 - Carteret County Dear Mr. Lewis: Director The Division of Environmental Management (DEM) has completed its modeling analysis of Calico Creek and has determined that both oxygen consuming wastes (CBOD, NH3-N, SOD) and eutrophication have a significant impact on the instream dissolved oxygen (DO) concentration. Removing the Morehead City WWTP will result in the greatest benefit to the stream and is considered the best alternative if it is economically feasible. If removing the WWTP is not a viable option, upgrading the WWTP will also greatly improve the instream water quality. A plant upgrade should include mechanisms to meet a summer BOD5 effluent limit of 5 mg/1 and an ammonia limit of 1 mg/l. If the plant consistently meets these limits, most of the subsequent DO deficit would be due to sediment oxygen demand (SOD). Since there are wide diurnal fluctuations in DO, a plant upgrade should also include technology for nutrient removal in order to meet instream target levels of total nitrogen (TN) and total phosphorus (TP) of 1 mg/1 and 0.05-0.1 mg/1 respectively. Further studies would need to be performed in order to deter- mine what the corresponding effluent limits would need to be. I have attached a copy of the modeling report for your review. If you have any questions, please contact Ruth Swanek or myself at (919)733-5083. Trevor Clements, Asst. Chief er Quality Section JTC/rcs cc: Preston Howard Boyd DeVane Central Files Pollution Prevention Pays P.O. Box 27687, Raleigh, North Carolina 27611-7687 Telephone 919-733-7015 A.. A MODELING EVALUATION OF THE WATER QUALITY IMPACTS TO CALICO CREEK FROM THE MOREHEAD CITY WASTEWATER DISCHARGE Prepared by N.C. Dept. of Environment, Health, and Natural Resources Division of Environmental Management Water Quality Section April, 1990 i A MODELING EVALUATION OF THE WATER QUALITY IMPACTS TO CALICO CREEK FROM THEIMOREHEAD CITY WASTEWATER DISCHARGE EXECUTIVE SUMMARY The Town of Morehead City is investigating wastewater disposal alternatives to accommodate its future growth needs. The munici- pality currently has a 1.7 MGD WWTP which discharges to Calico Creek in the White Oak River Basin. Dissolved oxygen concentra- tions as low as 0.5 mg/1 have been detected in Calico Creek by Morehead City. In addition, diurnal dissolved oxygen values indi- cate that eutrophication is a problem in Calico Creek. An orth Carolina Water Quality Analysis Program (NCWQAP) model (Stockton and Vogt, 1988) was calibrated to determine the effects of the WWTP loadings on the dissolved oxygen concentration. Oxygen -consuming wastes and eutrophication have the greatest impact on the instream dissolved oxygen concentration. However, no chlo- rophyll A data or photosynthesis/respiration data were available to determine the impacts from eutrophication. Therefore, modeling efforts focused on determining the proportion of the dissolved oxy- gen deficit due to the Morehead City effluent and the effect of reducing the point source loading of oxygen consuming wastes. The Imodel indicated that upgrading or removing the Morehead City WWTP will greatly improve water quality. With advanced ter- tiary treatment, the DO deficit due to the Morehead City WWTP is predicted to decrease by nearly 40 percent. DO violations of the stream standard may still occur due to sediment oxygen demand (SOD) and algal demand, but the average water quality conditions of this tidal stream should improve. If the plant is upgraded to meet advanced tertiary limits, nutrient removal technology should be included in the design to improve the trophic state of Calico Creek. I. BACKGROUND Morhead Cityis currentlyinvestigating land disposal methods g g p to accommodate future wastewater treatment needs. The Town plans on retaining its current treatment plant on Calico Creek, but the effluent may be causing instream water quality problems. Water quality and rhodamine dye studies indicate that a substantial por- tion of the the effluent remains in the channel throughout the tidal cycle. Self monitoring data indicate that dissolved oxygen concentrations as low as 0.5 mg/1 exist instream. If past dis- solved oxygen standard violations are primarily due to the Morehead City effluent rather than outside factors such as urban runoff, the Town should consider advanced treatment or land disposal for the Calico Creek effluent. II. FIELD STUDIES Two field studies were performed on Calico Creek by the North Carolina. Division of Environmental Management (DEM). The first involved a rhodamine dye injection study performed by DEM in September, 1981, and was used to evaluate pollutant transport in Calico Creek and to estimate dispersion coefficients within the NCWQAP model used by the Technical Support Branch. The second study was performed on September 20-21, 1988 by DEM to provide data for calibration of the water quality kinetics within NCWQAP. Long term BOD samples were collected along with dissolved oxygen (DO) profiles, sediment oxygen demand (SOD), temperature, pH, conducti- vity, salinity, and total phosphorus measurements. III. MODEL DEVELOPMENT a. Previous Modeling Analyses Calico Creek, located in the White Oak River Basin, is tidally influenced. The dye concentration data collected during the September, 1981 study were input to a superposition model (See Yotsukura and Kilpatrick, 1973) to estimate maximum allowable effluent BOD-ultimate (BODu) for the Morehead City WWTP. However, a thorough review of the original assimilative capacity analysis revealed several errors of substantial proportion. These errors and their subsequent impacts are detailed below: Error 1 -- The mass of dye actually used in the study was incorrectly estimated. A loading rate reflecting the overall mass of the 12 liters of dye solution (50.4 lbs/day) was used rather than a rate reflecting the actual mass of the (10r6 lbs/day) dye, which made up only 20 percent of the solu- tion. Therefore, the amount of dye assumed to be discharged was overestimated by a factor of five. In turn, instream dilution of the effluent dye concentration was overestimated by factor of five, and a much higher rate of dispersion was ass med than actually occurred. Err r 2 -- The first analysis incorrectly applied the theory of uperposition over space rather than over time for a given location. Therefore, the conclusions drawn from the analysis to etermine a wasteload allocation are in error. Error 3 -- The second analysis employed the superposition theory over time at a single instream station. This app ication ignored the actual dye distribution and was not ref ective of the region of greatest dye concentration build-up. In addition, daily (i.e. 24 hr) dye and effluent loa s were incorrectly input to the model which was based on dye observations at each tidal period (-12 hours). This had the effect of overestimating dilution by another factor of two! When taken into account with the error in the estimate of aye mass, assimilative capacity was overestimated by a fac- tor greater than ten. In addition to these errors, the method by which maximum allowable BOD-ultimate was determined ignored several mechanisms which appear to be of importance in Calico Creek. Allowable BOD was esti ated using the equation: Do - 1 Lo sgrt (p) * (-sgrt (p)) Where: Do = allowable DO deficit Lo = allowable BOD-ultimate p = assimilation ratio (K2/K1) K2 = Reaeration K1 = BOD Decay Rate This model ignores other sources of DO deficit such as sedi- ment oxygen demand (SOD) and net photosynthesis/respiration rates (P/R), both of which appear to be of importance in Calico Creek. Water quality data collected during the study showed large fluctua- tions in both DO and pH over the course of a day. According to Morehead City's consulting engineer, Tyndall Lewis, a rich organic material lines the bottom of Calico Creek and DO concentrations in the marshy areas are often measured at zero. These factors should have been'1taken into consideration in determining the remaining portion of deficit available for assimilation of the effluent. Other limitations of the model exist. The theory of superpo- sition model can only be used to estimate the impact of a single discharge emanating from the point of dye discharge, which substan- tially limits its management applicability. Also, the original application of the model lumps both CBOD and NBOD into a single parameter: BOD-ultimate (BODu). Recent studies demonstrate that carbonaceous and nitrogenous rates of decay can be quite different. DEM now routinely employs models which separate the two waste com- ponents. Although NBOD and CBOD could be simulated separately through superposition, the models would only be applicable for Morehead City's discharge. DEM ust analyze the effect of the Morehead City effluent on -2- DO in Calico Creek. Although the theory of superposition cannot be used directly to analyze the impact of the discharge, it can be used to help estimate dispersion in Calico Creek. In turn, this dispersion rate can be input to a finite section model (NCWQAP) recently developed by DEM (Stockton and Vogt, 1988) and adopted from Tho,ann (1987) to use as a tool in the DO analysis. b. Finite Section Model Description NCWQAP is a finite section model coupling CBOD and NBOD with DO and is based upon the following steady-state solution: for x >= 0, Dx = Do exp (u_ (l+aa ) x) + 2E Kd_ (exp f (u/2E) - (1-ad. , _ exp f (u(1-a,.} x�) CBOD Ka-Kd ad -' aa + Kn (exp f (u/2E) - (1-an,} xj_ _ exp f (u/2E) - (1-a',] NBOD Ka-Kn an aa + S/H (1-exp (-sgrt (KaL2/4E)) ) Ka Where: Dx = DO deficit at point x Do = Initial DO deficit u = Advective Velocity E = Rate of Dispersion Kd = CBOD decay rate Kn = NBOD decay rate Ka = Reaeration rate aa = sqrt(1 + 4KaE) u ad = sqrt(1 + 4KdE) u an = sqrt(1 + 4KnE) S = sediment oxygen demand rate H = depth L = segment length Model hydraulic characteristics (i.e. channel width & depth) and physical transport mechanisms (dispersion (E) and advective velocity (U)) were calibrated from the 1981 dye study. Model kinetics: NBOD decay (Kn) ; CBOD decay (Kd) ; and SOD were cali- brated using water quality data collected in September, 1988. c. Hydraulics Model se lentation -- Calico Creek was segmented in one dimension: longitudi7al. Complete horizontal and vertical mixing was assumed. -3- n• Segments are described below (see Figure 1): Seg. No. Description Length 1 From bridge @ SR1243 to Cross -Section # 1 1500 ft 2 From CS # 1 to CS # 3 1600 ft 3 From CS # 3 to CS # 4 1300 ft 4 From CS # 4 to CS # 5 2250 ft 5 From CS # 5 to CS # 6 1450 ft Depth -- Tidally -averaged depth was input in light of the cross - sectional area measurements collected during the 1981 intensive survey (Appendix A). Estimates are as follows: Estimated .Seg No. Depth (ft) 1 1.5 2 2.25 3 2.5 4 2.5 5 3.0 Width Tidally -averaged width was input as the average width of the cross -sections measured during the 1981 intensive survey (Appendix A). Estimates are as follows: Estimated Seg No. Width Lft ) 1 100 2 350 3 500 4 500 5 700 Cross -Sectional Area -- Cross -sectional areas must be input to reflect the segment boundaries. Using the cross -sectional measure- ments summarized in Appendix A, the following model inputs were used: Section Cross -Sectional 1__ Area (ft2l 1 100 2 200 3 1300 4 1700 5 2000 6 2800 Velocity -- More field data are necessary to estimate a reliable rate for net tidal velocity. Since there is little, if any, fresh- water input to this system during low flow periods (as was demon- strated by the salinity data in the 1981 study which ranged between 15 and 30 ppt), net tidal velocity is determined by tidal patterns and not freshwater flow. Ideally, multidirectional velocity meter measurements taken throughout the estuary over several tidal cycles -4- would allow an estimate of net tidal velocity. A partial measure- ment on 8/25/81 (Figure 2) taken at the 20th Street Bridge cannot be used effectively because it did not cover a full tidal cycle. Measurements taken at even increments (e.g. every hr) over an entire tidal day would be preferred for analytical purposes. The data generated from the partial measurement generally indicate that average incoming velocities approximate average outgoing velocities such that the net advective velocity is negligible although instan- taneous velocity can be as high as 1.2 fps. For the model, it was assumed that net advective velocity can be approximated by freshwater flow divided by cross -sectional area. Assuming that Morehead's discharge provides the only non -tidal flow, velocity in the segments below the discharge is expected to be approximately 0.001 fps. Dispersion -- As a first cut, dispersion was estimated using the method outlined in Thomann (1987), Principles of Surface Water Ouality Modeling and Control, pp 114-121. The method depends upon the availability of conservative tracer data. Dye data from a 1981 DEM Rhodamine dye study in Calico Creek were used to calculate rep- resentative dye distributions as tracers for high and low slack tides using the theory of superposition (Yotsukura, 1973, Tracer Simulation of Soluble Waste Concentration). The theory of superpo- sition isappropriate here since it is not being used to directly predict the effect of the effluent on water quality as it was in earlier applications. The theory is being used only to estimate dye concentrations which in turn will be used to estimate the dis- persion coefficients which will be input into an appropriate water quality model. The resulting tidal dye concentrations are summarized spatially in Figures 3 and 4. A "tidally averaged" dye concentration was estimated by averaging the highand low slack accumulated dye concentrations at each station (Figure 5). Dispersion was estimated for all three conditions: Low tide, high tide, and tidal average. Tracer dye concentrations are related to dispersion via the follow- ing equation: Nei x-ut 2 S = 2A (sgrt (3.14Et)) exp [ -4Et ] Where: S = dye concentration M = mass of dye discharged A = cross -sectional area E = dispersion u = advective velocity x = distance from dye dump t = time A plot of'ln S versus (x-ut)2 can be fit with a line, the slope of which is (-(4Et)]. Dispersion (E) can then be solved for using -5- this relationship: E = -(slope 4t) -1 Low tide: Ordinary least squares (OLS) regression of In dye concentlration versus distance (x) from outfall Mote: advective velocity (u) was assumed to be effectively zero for purposes of this ca culation. Therefore, "ut" drops from consideration) yielded a slope of - 1.798 per square mile. Dye concentrations were accumulated over 6 tidal cycles (i.e. t = 6 * 0.518 day = 3.108 were 0.518 = time of 1 tidal cycle) . (Figure 6) E = (1.798 * * 3.108) -1 = 0.045 mi2/day /day High tide: slope of regression = - 2.394 (Figure 7) E = (2.394 * * 3.108) -1 = 0.033 mi2/day /day Tidal average: slope of regression = -1.883 (Figure 8) E = (1.883 * * 3.108) -1 = 0.043 mi2/day /day Therefore, a dispersion rate of 0.04 mi2/day was initially input to each model section. Dispersion rates were adjusted to fit the tidally averaged dye profile generated from the superposition waste input of dye, and boundary conditions were required for this analysis. The wasteflow discharge during the dye study was not reported, and self - monitoring records for 1981 have long since been archived. Based upon monthly average flows provided in the wasteload file notes, a flow of sightly more than 1 MGD was assumed. An effluent dye con- centration of 1200 ug/1 was used based upon this wasteflow and a dye mass loading rate of 10.6 lbs/day. A single rate for dispersion did not appear to represent the data well (Figure 9). However, given the physical characteristics of Calico Creek, this was expected. The upper portion of Calico Creek is narrow, relatively shallow, full of vegetation, and fur- ther away from the open sound: a lower rate of dispersion would apply in the upper section of Calico Creek. Calico Creek below Piggotts Bridge begins to both widen and deepen: the rate of dis- persion should increase in the lower section of Calico Creek as open sound mixing mechanisms begin to play a greater role. Through trial and error, the following dispersion coefficients were settled .,f on as acceptable for modeling purposes (Figure 9): Section Dispersion (mi?/day) 1 0.03 2 0.05 3 0.05 4 0.10 5 0.15 6 0.15 d. CBOD Calibration Long term BOD samples were collected in September, 1988 at each of tihe sampling locations. Barnwell's BOD model software was used to estimate the bottle BOD ultimate (BODu) and decay rate. Initial and periodic nitrogen measurements were made during the analysis. NBOD was then estimated by the following equation: CBOD was then NBOD = 4.5*(Final NOx - Initial NOx) estimated at each site by: CBOD = BODu - NBOD Based upon the resulting CBOD values, the following rates were chosen to represent the CBOD kinetics: CBOD Decay = 0.1 /day CBOD Settling = 0 /day It was assumed that the CBOD settling rate would be negligible due to the turbulence caused by the tide. The sludge lining.the stream bed contrdicts this assumption, but it was assumed that the sludge was primarily background organic matter rather than material from the WWTP. The model also underpredicted CBOD when settling was included, and the predicted concentrations declined at a faster rate than those observed instream. Input of even relatively low CBOD decay rates also caused the CBOD concentration to be underpredicted. Figure 10 shows the predicted and observed CBOD concentrations at a CBOD decay rate of 0.1 /day which is at the lower end of the literature values (Driscoll et al., 1983). A CBOD decay rate of zero was input for comparative purposes (Figure 11), and it resulted in a better curve match. However, it would not make sense to assume that none of the CBOD was subject to decay. In addition, the bottle decay rates were approximately 0.08 /day which indicates that an instream decay rate of 0L1 /day is more appropriate since instream decay rates are usually slightly higher than the bottle values. It was hypothesized that transport assumptions might have influenced the predicted CBOD profile. The dispersion rates used from the dye study calibration may have been too high for the water quality clibration, perhaps due to differences in the wind and atmospheric pressure during the separate sampling periods. In -7- 2 ti addition, the method of estimating dispersion coefficients results only in a ballpark figure of the actual value. As a trial, the dispersion rates were changed to the following: Section Disp. Set 1 (mid/d) Disp. Set 2 (mid/d), 1 0.015 0.0075 2 0.025 0.0125 3 0.025 0.0125 4 0.050 0.0250 5 0.075 0.0375 6 0.075 0.0375 The first set of dispersion coefficients resulted in a curve (Figure 12) which had a similar slope to the observed data, and these dispersion values were used in the remainder of the water quality model calibration. Table 1 shows the results of using the second set of dispersion coefficients. The negative CBOD value in the upper reach indicates that these dispersion rates were too low. e. Nitrogen Calibration The model kinetics for organic nitrogen and ammonia were also calibrated using the data collected in September, 1988. The fol- lowing rates were chosen: Org. N Hydrolysis = 0.05 /day Org. N Settling = 0 /day Ammonia Oxidation = 0.5 /day An organic nitrogen decay rate of 0.05 /day, which is at the low end of the literature range (Driscoll et al., 1983), was chosen since the slope of the resulting predictions (Figure 13) approxi- mated that of the observed data, although the concentrations were underpredicted. Again, it was assumed that settling would be zero due to the turbulence caused by the tide, and the organic material lining th stream bed was due to background conditions. A high literature rate of 0.5 /day (Driscoll, et al., 1983) was chosen for ammonia oxidation since it was assumed that turbulence caused by the tide would increase the rate. This theory was substantiated by the data.' A level of 4.6 mg/1 was observed in the WWTP effluent, but the values observed instream were relatively constant at 0.03 mg/l. The difference between instream and effluent ammonia was notably larger then the difference between effluent and instream ¶BOD, and thus oxidation was suspected rather than trans- port. The model results are summarized in Table 2. f. SOD SOD data were collected by EPA and DEM in September, 1988 in Calico Creek using an in -situ chamber method. Five replicate samples wereanalyzed, and the resulting values ranged from 2.02 to 2.65 g 02/m- day (Table 3) with an average value of 2.25 g 021/m2-day. Members of the DEM survey team expected higher values of SOD. They thought the area sampled may not be indicative of most of Calico Creek (Figure 1) as it is located in an oyster and shellfish area. In addition, the SOD chambers were set up -8- during high tide and the bottomcontours could not be seen. When the tide went out it was determined that the chambers were set up on a mound. This area probably has less organic material than the lower ardas surrounding the chambers. Therefore, the model was run at the average SOD (2.25 g 02/m22day) and at 4 and 6 g 02/m2-day. The model runs at 4 and 6 g 02/m day are included in the "Sensiti- vity Analysis" section. IV. PREDICTING DISSOLVED OXYGEN Dis olved oxygen (DO) is modeled as a function of several mechanis s: CBOD decay, NBOD decay, SOD, reaeration, and net photo- synthesis/respiration (P/R). Of these, reaeration and net P/R were not measuyred in the field. Since reaeration was unknown, the model was run at reaeration rates ranging from 1 to 10 /day at an SOD rate of 2.25 g 02/m day. At a rea ration rate of 1 /day, the deficit exceeded DO saturation (approxi ately 7 mg/1) which indicates this value is too low. At reaerati n rates greater than 3 /day, reaeration dominated the stream, and SOD and the effluent had little effect on the instream DO. Therefore, reaeration rates of 2 and 3 /day were examined in the analysis. Net P/R appears to be an important factor influencing DO in Calico Creek. The field notes from September 20, 1988 indicate that the ater was green with algae from upstream of the WWTP to the mout of Calico Creek. The algae affect the net P/R and instream 0 by producing oxygen during the daylight hours through photosynthesis and depleting the water column oxygen at night through respiration. The low DO concentrations (Table 4) measured by the Town of Morehead City show this phenomenon. The Town collects its data at approximately 8:00 AM each day, and the low values arse influenced by phytoplankton respiration. DEM collected DO data over a 24 hour period on September 20-21, 1988 at the 20th Street Bridge (Piggotts Bridge), and the diurnal variation in the DO data (Table 5) show the importance of net P/R in the system. Table 5 also shows the affect of the tide on DO. The highest DO value occurred at approximately 4:00 in the afternoon during high tide. This value was affected by the high rate of photosynthesis which occrs during the afternoon hours (i.e. high P/R) and the tide. During high tide, water from the sound partially dilutes concentrations of the water quality parameters in Calico Creek. During low tide, the system is dominated by the Morehead City effluent. This is further supported by the data. In a lake or riverine system, one would expect the DO to decrease throughout the night as photosynthesis ceases and respiration continues. However, the DO concentrations began to rise after the low tide which occurred t 11:00 PM since dilution began as the tide brought with it a large volume of water with higher DO concentration. After initial mixing with the high tide, DO concentration continued to decrease until photosynthesis began to affect the system between 8:00 and 9:00 AM. Alth ugh the P/R ratio is important to the system, it should -9- not effect the results of the modeling analysis since the model was not used to estimate concentrations of various parameters directly. Instead, the primary purpose of the modeling analysis was to deter- mine the leffect of Morehead City's effluent CBOD and ammonia on the DO deficit in Calico Creek (i.e. what proportion of the deficit is a result of the effluent). Therefore, the P/R ratio could be set at a given level, and DO concentrations could be compared while changing characteristics of the Morehead City effluent. In order to determine what percentage of the deficit was from wastewater, the model was run with and without wastewater loadings at reaeration rates of 2 and 3 /day. It was run at the current effluent limits of 30 mg/1 BOD5, 10 mg/1 NH3, 5 mg/1 DO, and 1.7 MGD of effluent flow. Morehead City does not have an effluent ammonia limit, but monitoring data indicate that the facility can meet 10 mg/1 during the summer months. Therefore, this value was used since a concentration was needed for model input. In order to determine if more stringent limits would help protect water quality, the model was also run at advanced limits of 5 mg/1 BOD5, 1 mg/1 NH3, 5 mg/1 DO, and 1.7 MGD of flow. Background nitrogen and BOD conditions in the no effluent model were obtained from data collected in the Newport River on September 20, 1988. In the advanced treatment model, the dilution between the current effluent and upstream concentrations was used to estimate background condi- tions assuming the dilution ratio would remain the same. The result was compared to the background conditions in the Newport River. The more conservative of the two estimates was used in the model. For all model runs, the background DO was calculated using self monitoring temperature data from the summer of 1988. Per Division procedure which is supported by EPA, the 75th percentile temperature was calculated (Table 6), and salinity data collected in September, 1988 were used to estimate chlorinity (Bowie, et al., 1985). The temperature and chlorinity values were then used to calculate saturation DO from Table 7. For most riverine systems, DEM assum9s that background DO is at 90% saturation, but upstream DO was assumed to be at 80% saturation in this situation since tidally influenced waters usually have lower DO concentrations. The downstream background DO was assumed to be 90% of saturation DO. Thus upstream background DO used in the allocation runs was 5.7 mg/1, while downstream DO was 6.3 mg/l. In all model runs, the CBOD and nitrogen decay rates were assumed to be equal to those obtained during model calibration. Changing the effluent load could affct the decay rates, but the calibrated rates were the best available, and were therefore used. The model results indicate that the greatest impact on DO occurs in Segments 1 and 2, the upstream segment and Calico Creek just below the outfall. Therefore, more emphasis was placed on these areT.s when interpreting the results. The results were as follows: Segment 1, Qw = 1.7 MGD, BOD5 = 30 mg/1, NH3 = 10 mg/1, DO = 5 mg/1 Ka=2 /day Ka=3 /day Deficit Deficit (mg/1) (mg/1) Deficit Deficit Due to Waste Deficit Due to SOD Total 2.7 1.8 45 3.3 2.3, 55 6.0 4.1 Segment 1, Qw = 1.7 MGD, BOD5 = 5 mg/1, NH3 = 1 mg/1, DO = 5 mg/1 Ka=2 /day Ka=3 /day Deficit Deficit (mg/1) (mg/1) Deficit Deficit Due to Waste 0.4 0.3 Deficit Due to SOD 2 Total 3.7 2.6 Segment 2 11 89 , Qw = 1.7 MGD, BOD5 = 30 mg/1, NH3 = 10 mg/1, DO = 5 mg/1 Ka=2 /day Ka=3 /day Deficit Deficit (mg/1) (mg/1) Deficit Deficit Due to Waste 4.4 3.1 Deficit Due to SOD 2.2 1.5 Total 6.6 4.6 Segment 2, 67 33 Qw = 1.7 MGD, BOD5 = 5 mg/1, NH3 = 1 mg/1, DO = 5 mg/1 Ka=2 /day Ka=3 /day Deficit Deficit (mg/1) (mg/1) Deficit, Deficit Due to Waste 0.8 0.6 28 Deficit Due to SOD 2.2 1.5, 72 Total 3.0 2.1 The results indicate that at the present effluent limits, the waste is responsible for 45% of the DO deficit in the upstream por- tions of Calico Creek and approximately 2/3 of the deficit just below the outfall. Improving the treatment technology in order to meet limits of 5 mg/1 BOD5 and 1 mg/1 NH3 would result in a system similar to one without waste. Under this scenario, most of the DO deficit would be the result of SOD. Violations of the DO standard would probably still occur since saturation DO is approximately 7 mg/1 in the summer and the deficit is expected to remain at 2 to -11- 3 mg/1, but the instream DO would greatly improve over current lev- els which drop as low as 0.5 mg/l. TheSOD rate may decrease with advanced treatment which would farther improve water quality, but the measured rate of 2.25 g 02/m -day is not a high rate for an estuary, and it was therefore assumed for modeling purposes that SOD would remain the same. Advanced treatment could also change the net P/R ratio since fewer nutrients would be discharged to the system. Therefore, fewer algae would be produced. However, net P/R could not be included in the model without more supporting field datFa. V. SENSITIVITY ANALYSIS Since modeling is not an exact science, it is important to know the limitations of the model. The inputs to the NCWQAP dis- solved oxygen model were estimated based upon the available data. Since steam systems vary, it is important to note how a change in a given input will change the concentration of the output parame- ters. Therefore, further model runs were performed while changing in certain puts. The SOD was changed to 4 and 6 g 02/m day due to the reas'ns cited earlier. The reaeration was changed simulta- neously ince it was suspected that reaertion would be high due to the turbulence caused by the tide. When the SOD was increased, the reaeration was increased in order to obtain DO concentrations which were similar to those obtained in the original model. The results indicated that the model was not too sensitive to reaeration. At an SOD rate of 4 g 02/m2-day, the reaeration rate was between 3 and 4 /day, while an SOD rate of 6 g 02/m -day resulted in a reaeration rate between 4 and 5 /day. In ddition to the uncertainty in the SOD measurement, there was uncertainty in the tidally averaged width and depth measurements. Since the tidal amplitude is approximately 3.5 feet in Calicl Creek, and the area is marshy, it was difficult to obtain accurate width measurements. In addition, there are sandbars near the mouth of the creek which make estimating a tidally averaged depth difficult. Therefore, additional model runs were performed to test the model sensitivity to the stream's physical characteris- tics. TY a first set of model runs involved changing the width. The modewas run at an SOD rate of 2.25 g 02/m day, a reaeration rate of 3 /day, an effluent flow of 1.7 mgd, an effluent BOD5 concentration of 30 mg/1, an effluent ammonia concentration of 10 mg/1, and an effluent DO concentration of 5 mg/l. The width in each model segment was halved and doubled. The results were as follows: 1/2 Width Orig. Width 2x Width Sea DO (mg/1) DO tmg/1) DO (mg/1) 1 2.17 3.08 3.82 2 1.72 2.53 3.39 3 3.71 4.36 4.91 4 4.78 5.11 5.36 5 5.49 5.59 5.66 -12- The results indicate that the model is sensitive to width. However, tionate c the field reasonabl sitive to arge changes were made in the width input, and a propor- ange did not occur in the dissolved oxygen. Members of survey team thought the original width estimates appeared . The results also indicate that the model is more sen- width in the upper reaches of Calico Creek. Usin the original width estimates and the same model inputs described above, the depth in the last segment was reduced from 3 feet to 2.5 feet. Dissolved oxygen decreased 0.14 mg/1 in the last (fifth) segment and 0.03 mg/1 in the fourth segment. This indi- cates that the model is not very sensitive to depth. VI. NUTRIENTS AND EUTROPHICATION Eutrophication is a problem in Calico Creek. Algae gives the water a greenish color, and the phytoplankton cause diurnal varia- tion in tie dissolved oxygen. The effluent is contributing to the nutrient oading as shown by the following effluent data from May, 1988 to Aril, 1989: Average Maximum Minimum NH3 (mg/1) 6.47 9.59 2.32 TN (mg/1) 18.43 25.60 9.90 TP (mg/1) 3.36 7.05 1.80 Staff of the Environmental Sciences Branch estimate that target levels of 1 mg/1 total nitrogen (TN) and 0.05 mg/1 total phosphorus (TP) are needed instream in order to prevent excessive phytoplankton growth in an average aquatic community. These num- bers are conservative, and the TP target level may be too conserva- tive for Calico Creek given the large changes in flow caused by the tide. Wi hout further studies, it is difficult to determine an appropria a TP target level, but a concentration of 0.1 mg/1 may be more practical. The CBOD data collected indicate that the dilution ratio is between 1 and 2. In other words, when a given substance is dis- charged, it will show up instream at a concentration between one half the effluent concentration and the effluent concentration. Therefore; in order to meet instream target TN and TP concentra- tions, the effluent concentrations of TN and TP should not exceed 2 mg/1 and 0.1-0.2 mg/l, respectively. The nutrient data collected by DEM in September, 1988 (Table 8) indicate that the nutrients are being used immediately by the phytoplankton as shown by.the low levels of nitrogen and phosphorus in the upstream portion of Calico Creek. Since the measurements were taken at mid tide, part of the low concentration may be due to dilution from tidal waters. If chlorophyll a and/or phytoplankton data were available, the effect of nutrients on the system would be easier to document. VII. DISCUSSION AND RECOMMENDATIONS The consumin consumin stimulat fluctuat phytopla main impacts on DO in Calico Creek come from oxygen waste (CBOD, NH3, SOD) and eutrophication. The oxygen - wastes deplete the oxygen supply, while eutrophication d by the point source nutrients causes diurnal ons in the DO due to respiration and photosynthesis by kton. Morehead City currently has three options for its Calico Creek WWTP: (1)1 continue to discharge at present effluent concentrations, (2) upgr de the Calico Creek WWTP to meet advanced limits, and (3) remove t e Calico Creek WWTP. If the Town continues discharging at its Ares nt limits, the DO and eutrophication problems will persist instream It is difficult to determine what proportion of the nutrients discharged are being used by algae without corresponding chlorophyll A (chl_a) and/or phytoplankton data. Algal growth potential tests (AGPT) would also help determine the level of bioavailable nutrients discharged from the Calico Creek WWTP. Research in other systems has indicated that very little nonpoint nitrogen and phosphorus is bioavailable (Raschke and Schultz, 1987). t is therefore likely that the best method to combat the eutrophi ation is through removal of the discharge or by implement- ing waste treatment technology to remove nitrogen and phosphorus. Upgrading the treatment plant will greatly improve the instream water quality by increasing the DO. It is expected that most of the subsequent DO deficit would be due to SOD. Any treat- ment plant upgrade should include technology to remove nutrients to meet or approach instream target levels of TN and TP of 1 mg/1 and 0.05-0.1 mg/1 respectively. Further studies would be needed to determine what the effluent limits would need to be in order to meet the instream target levels. AGPT tests would indicate whether the system is nitrogen or phosphorus limiting. Since saline waters are usually nitrogen limiting, the limiting nutrient is probably nitrogen. The total nitrogen to total phosphorus (TN:TP) ratio also supports the conclusion that Calico Creek is currently nitrogen limited. The TN discharged on September 20, 1988 was 12.1 mg/1 whi e the TP was 2.8 mg/1 resulting in a TN:TP loading ratio of 4.3. Since an instream TN:TP ratio between 11:1 and 15:1 is needed f r maximum algal growth (Raschke and Schultz, 1987), the low rati suggests that the system is nitrogen limited. Also, the more rapid loss of ammonia -nitrogen (NH3-N) and nitrite -nitrate (NO2+NO3) from the system than occurred for phosphorus (see concentration profiles in Table 8) supports this hypothesis. Therefore, unless the system can be driven to a phosphorus limiting state, reduction in effluent TN will have a larger impact on eutrophi c ation than reduction in TP. Removal of the WWTP will result in the greatest improvement in water quality. -Eutrophication will decrease due to fewer bioavailable nutrients and subsequently, the magnitude of diurnal DO variations would be expected to decrease. Minimum DO concentra- tions would be expected to increase. The resulting DO deficit would be due almost entirely to SOD, and the SOD rate may even -14- a decrease since effluent sludge would not be deposited in the creek bed. However, this decrease would probably not be substantial since the levels measured in Calico Creek were not extremely high when compared to other estuaries. In ,ummary, DEM recommends that the Calico Creek WWTP be removed or upgraded to meet advanced limits. Plant removal will result in the greatest improvement in water quality and is the best alternative if it is economically feasible. A significant plant upgrade would also increase instream DO concentrations, but it should include advanced technology for nutrient removal in order to improve the trophic state of Calico Creek and to reduce the magni- tude of iurnal variation in DO. Literature Cited Bowie, George L., William B. Mills, Dinal B. Porcelia, Carrie L. Campbell, John R. Pagenkopf, Gretchen L. Rupp, Kay M. Johnson, Peter W.H. Chan, and Steven A. Gherini. 1985. Rates, Con- stants. and Kinetics Forumlations in Surface Water Oualitv_ M 'lin , Second Edition. Athens, Ga.: Environmental Res arch Laboratory, Office of Research and Development, U.S. Environmental Protection Agency. Driscoll Eugene El, John L. Mancini, and Peter A. Mangarella. 1983. Technical Guidance Manual for Performing Waste Load n�. Washington DC: Office of Water Regulations and Staidards, Monitoring and Data Support Division, Monitoring Branch of the U.S. Environmental Protection Agency. Raschke, Ronald L. and Donald A. Schultz. 1987. "The Use of the Algal Growth Potential Test for Data Assessment," Journal Water Pollution Control Federation, 59:222-227. Stockton, Thomas B. and J. David Vogt. 1988. DEM's Technical Support Branch has model for internal use. Thomann, Robert V. and John A. Mueller. 1987. Principles of Sur- face Water Ouality Modeling and Control. New York: Harper & Row. Yotsukura, Nobubiro, and Frederick A. Kilpatrick. 1973. "Tracer Simulation of Soluble Waste Concentration," Journal of the Environmental Engineering Division, 99:499-515. Data collected in a tidal system usually must be translated to a midwater position as described in the Brunswick Estuary Modeling Project (1983)since samples are usually collected at high water and low water slack while models are set up for mean tide data. The 1988'water quality data were collected at midtide, and the method described in the Brunswick Estuary report did not yield valid results. Therefore, the figures included in this report have both the high to low and low to high tide points plotted rather than tidally averaged points. * From State of Georgia, Dept. of Natural Resources, Environ- mental Protection Division, Atlanta, Ga. 1983. Brunswick Estuary Modeling Project: Manual for Instruction for Estuary Modeling. Hydroqual Inc: Mahwah, NJ. X1 X2 X3 X4 PIGGOTTS BRIDGE X5 MOREHEAD CITY FIGURE 1; CALICO CREEK STUDY AREA AND CROSS SECTIONS a LL VELOC ITY 1.2 1 - 0.8 - 0.6 - 0.4 - 0.2 - 0 Figure 2 CALICO CREEK VELOCITY VS. TIME (8/25/81) - 0.2 - - 0.4 - - 0.6 - -0.8 - -1 - - 1.2 - - 1.4 7:55 1 8:34 10:20 1 10:53 13:05 TIME OF DAY 1 13:20 1 14:02 1 14:20 1 14:40 16:05 1.8 99 311 WWTP 91 32 30 13.8 PIGGOTTS BRIDGE 1.8 11.6 Q ()CALICO CREEK MOREHEAD CITY FIGURE 3: HIGH SLACK TIDE ACCUMULATED DYE CONCENTRATION (9/9-12/81) 0 0.95 1.4 Y u 132 l 800.(ASSUMED) N J WWTP 1.2 3 536 254 160 7.1 100 28.85 0 54 Q (DC CREEK PIGGOTTS BRIDGE MOREHEAD CITY FIGURE 4: LOW SLACK TIDE ACCUMULATED DYE CONCENTRATION (9/9-12/81) 0 4.0 116 600 1.6 ,mom WWTP 314 143 57 PIGGOTTS BRIDGE 16 33 Q 0 CALICO CREEK MOREHEAD CITY FIGURE 5: TIDALLY AVERAGED ACCUMULATED DYE CONCENTRATION (9/9-12/81) 0 20.5 7 Figure 6 DISPERSION IN CALICO CREEK, NC Low Tide Dye Concentrations DYE CONC. (LN ug/1) 0 0 6-- 5 4 3 2 0 0 1 0 0 1 0.4 i 0.8 i 1.2 i 116 1 1 SQUARED DISTANCE FROM OUTFALL (MIA2) 0 OBSERVED PREDICTED 2 Figure 7 DISPERSION IN CALICO CREEK, NC High Tide Dye Concentrations DYE CONC. (LN ug/i) 0 0.4 0.8 1!2 1.6 SQUARED DISTANCE FROM OUTFALL (MIA2) 0 OBSERVED PREDICTED 2 u DISPERSION IN CALICO CREEK, NC Tidally -Averaged Dye Concentrations DYE CONC. (LN ug/1) 0 0 1 1 0.4 1 1 0.8 1 1 1.2 1 SQUARED DISTANCE FROM OUTFALL (MIA2) 0 OBSERVED PREDICTED 1 1.6 1 2 OBSERVED VS PREDICTED DYE CONCENTRATION CALICO CREEK, CARTERET COUNTY VVLJ q U Z O Q z Q 0 Z c4 500 — 400 - 300 — 200 —, 100 0 + o .� + o 0 L + 0 p c + 0 1 1 1 I I I 1 1 I 0 OBSERVED -1 1 3 (Thousands) DIST. (FT) FROM MOREHEAD CITY OUTFALL + E=0.04 0 E=0.05 7 0 E varied 34 32 30 28 26 24 N CD 22 z 20 a m 18 0 16 14 12 10 8 6 CALICO CREEK CBOD CBOD DECAY = 0,1, ORIGINAL DISPERSION 0 0 + O 0 * Q 0 + 0 1 0 PREDICTED 3 (Thousands) DISTANCE FROM WWTP IN FEET + OBSERVED LO—HI 1 5 0 OBSERVED HI—LO 34 32 Figure 11 CALICO CREEK CBOD CBOD DECAY = 0, SETTLING = 0 30 28 26 24 J N CD 22 Z 20 m 18 0 16 14 12 10 8 6 + 0 0 + 0 o ill 0 0 + Q 0 t 1 Q PREDICTED 3 (Thousands) DISTANCE FROM WWTP IN FEET + OBSERVED LO—HI 1 5 0 OBSERVED HI—LO 34 3 Figure 12 CALICO CREEK COD CBOD DECAY = 041, 1/2 DISPERSION RATES 30 28 26 24 N 22 cp 20 z p 18 0 m 16 0 14 12 10 8 6 4 0 0 11 0 0 + 0 0 + 1 ci PREDICTED 3 (Thousands) DISTANCE FROM WWTP IN FEET + OBSERVED LO—HI 1 5 0 OBSERVED HI—LO 7 2.6 CALICO CREEK ORGANIC NITROGEN ORG N DECAY = 0.05, ORG N SETTLING = 0 2.4 2.2 2 1.8 J 0 1.6 2 — 1.4 z 1.2 tt 1 0.8 0.6 0.4 0.2 + 0 + 0 0 0 4 0 + 0 0 + 0 —1 0 PREDICTED 3 (Thousands) DISTANCE FROM WWTP IN FEET + OBSERVED LO—HI 1 5 0 OBSERVED HI—LO Table 1: Table 2: Observed and Predicted CLOD where Kd = 0.1 /day and E - 0.25(Calculated Rates) Segment Predicted Observed No. (mg/1) (mg/1) 1 -0.15 30.73 2 42.54_ 24.39 3 14.72 14.08 4 2.74 9.93 5 0.50 7.45 Observed and Predicted Ammonia - NH3 Oxid. = 0.5 /day Segment Predicted Observed No. (mg/1) (mg/1) 1 0.09 0.02 2 0.37 0.03 3 0.07 0.03 4 0.01 0.01 5 0.00 0.04 Table 3: SOD Rates in Calico Creek - August, 1988 Samples taken at CC-1 SOD Replicate (g O2La -day) , Mean 1 2.02 2 2.33 3 2.18 4 2.08 NC 2.65 2.25 Data collected by U.S. Environmental Protection Agency and North Carolina Division of Environmental Management Table 4: Tnstream Self -Monitoring Data (4/89, 5/88-10/88) Upstream Location: Country Club Blvd. Downstream Location: N. 20th Street (Piggotts Bridge) Upstream Upstream Downstream Downstream DO % D0 DO % DO (mg/1) Sat. (mg/1) , Sat. Average 3.26 37 4.12 47 Maximum 8.00 88 7.20 83 Minimum 0.50 6 1.30 15 Table 5: Instream DO measured by DEM 9/20-21/88 20th Street (Piggotts Bridge) DO• Time (mg/1) Tide 1100 10.82 1200 11.12 1300 9.25 1400 8.72 1500 8.67 1600 16.97 High 1700 12.10 1800 12.57 1900 11.69 2000 9.93 2100 7.24 2200 5.03 2300 3.25 Low 2400 5.12 100 6.16 200 5.55 300 5.78 400 6.41 High 500 4.16 600 3.95 700 2.73 800 2.47 900 4.51 1000 9.03 Low 1 1 � Table 6: Morehead City Instream Monitoring Data (Summer) Obs date 1 11-Jul -88 2 18-Jul -88 3 24-Jun-88 4 15-Jul -88 5 20-Ju1-88 6 27-Ju1-88 7 03-Aug-88 8 08-Aug-88 9 19-Aug-88 10 22-Jun-88 11 13-Jul -88 12 29-Jul -88 13 01-Aug-88 14 05-Aug-88 15 10-Aug-88 16 12-Aug-88 17 17-Aug-88 18 18-Aug-88 19 22-Aug-88 20 24-Aug-88 21 26-Aug-88 22 29-Aug-88 23 19-Sep-88 24 23-May-88 25 20-Jun-88 26 22-Jill -88 27 25-Jul -88 28 14-Sep-88 29 21-Sep-88 30 23-Sep-88 31 03-Oct-88 32 03-Jun-88 33 01-Jun-88 34 08-Jun-88 35 17-Jun-88 36 27-Jun-88 37 08-Jul -88 38 31-Aug-88 39 26-Sep-88 40 02-Sep-88 41 09-Sep-88 42 12-Sep-88 43 15-Jun-88 44 06-Jul -88 45 28-Sep-88 46 30-Sep-88 47 16-May-88 48 10-Jun-88 49 13-Jun-88 50 01-Jul -88 51 07-Sep-88 52 16-Sep-88 53 06-Jun-88 54 05-May-88 55 10-Oct-88 56 09-May-88 57 17-Oct-88 58 24-Oct-88 59 03-Apr-89 60 24-Apr -89 61 17-Apr -89 62 31-Oct-88 63 10-Apr-89 up up up up down down down down e temp (c) DO DO sat % sat temp (c) DO DO sat % sat 08:00 27.00 2.00 7.97 0.25 27.00 4.10 7.97 0.51 08:00 27.00 1.40 7.97 0.18 27.00 1.90 7.97 0.24 08:30 26.50 7.10 8.04 0.88 27.00 4.40 7.97 0.55 08:05 26.00 3.10 8.11 0.38 27.50 3.90 7.89 0.49 07:55 26.00 1.90 8.11 0.23 26.00 3.40 8.11 0.42 08:10 26.00 0.50 8.11 0.06 28.00 2.90 7.83 0.37 08:00 26.00 2.30 8.11 0.28 27.00 5.20 7.97 0.65 08:02 26.00 2.30 8.11 0.28 26.00 2.30 8.11 0.28 08:20 26.00 1.90 8.11 0.23 27.50 3.00 7.89 0.38 08:15 25.50 6.20 8.19 0.76 26.00 4.30 8.11 0.53 08:00 25.00 2.00 8.26 0.24 26.00 5.10 8.11 0.63 07:55 25.00 0.90 8.26 0.11 26.00 2.30 8.11 0.28 08:05 25.00 3.20 8.26 0.39 27.00 2.80 7.97 0.35 07:55 25.00 2.90 8.26 0.35 26.00 4.30 8.11 0.53 07:55 25.00 3.10 8.26 0.38 25.00 4.30 8.26 0.52 08:05 25.00 2.90 8.26 0.35 25.00 3.50 8.26 0.42 08:15 25.00 3.50 8.26 0.42 25.50 4.20 8.19 0.51 08:00 25.00 3.10 8.26 0.38 26.00 2.40 8.11 0.30 07:55 25.00 4.20 8.26 0.51 24.00 2.50 8.42 0.30 08:10 25.00 2.80 8.26 0.34 26.00 2.40 8.11 0.30 08:30 25.00 1.50 8.26 0.18 27.50 3.20 7.89 0.41 08:00 25.00 1.80 8.26 0.22 26.00 3.20 8.11 0.39 08:03 24.50 2.20 8.34 0.26 22.50 2.70 8.66 0.31 08:05 24.00 3.20 8.42 0.38 24.00 1.80 8.42 0.21 08:10 24.00 7.20 8.42 0.86 26.00 6.70 8.11 0.83 08:10 24.00 3.50 8.42 0.42 24.00 1.90 8.42 0.23 08:05 24.00 2.60 8.42 0.31 26.00 2.60 8.11 0.32 08:00 24.00 1.20 8.42 0.14 24.00 4.70 8.42 0.56 08:00 24.00 2.20 8.42 0.26 25.00 4.60 8.26 0.56 07:55 24.00 2.50 8.42 0.30 24.00 4.70 8.42 0.56 08:15 24.00 4.20 8.42 0.50 23.50 2.10 8.49 0.25 23.30 3.00 8.53 0.35 23.00 6.50 8.58 0.76 23.00 2.30 8.58 0.27 23.00 6.00 8.58 0.70 08:30 23.00 3.70 8.58 0.43 23.50 4.60 8.49 0.54 08:00 23.00 4.50 8.58 0.52 23.00 4.00 8.58 0.47 08:10 23.00 2.00 8.58 0.23 25.00 1.70 8.26 0.21 08:05 23.00 2.90 8.58 0.34 23.00 2.00 8.58 0.23 09:00 23.00 4.10 8.58 0.48 23.00 4.80 8.58 0.56 08:00 23.00 4.40 8.58 0.51 23.50 5.50 8.49 0.65 07:55 22.00 4.20 8.74 0.48 22.50 1.30 8.66 0.15 07:55 22.00 1.20 8.74 0.14 23.00 4.70 8.58 0.55 08:00 22.00 1.20 8.74 0.14 23.00 5.40 8.58 0.63 08:00 21.00 2.10 8.91 0.24 24.00 3.70 8.42 0.44 08:05 21.00 6.10 8.91 0.68 21.00 4.20 8.91 0.47 08:00 21.00 3.70 8.91 0.42 22.00 4.80 8.74 0.55 08:10 21.00 2.00 8.91 0.22 22.00 4.80 8.74 0.55 08:15 20.00 2.30 9.09 0.25 20.50 4.90 9.00 0.54 08:10 20.00 3.90 9.09 0.43 21.00 3.60 8.91 0.40 07:57 20.00 3.10 9.09 0.34 21.00 4.30 8.91 0.48 08:00 20.00 2.30 9.09 0.25 21.00 4.70 8.91 0.53 08:15 20.00 2.50 9.09 0.28 20.50 4.60 9.00 0.51 08:05 20.00 1.70 9.09 0.19 21.00 4.20 8.91 0.47 08:00 18.00 3.10 9.46 0.33 18.00 5.90 9.46 0.62 08:15 16.00 4.30 9.87 0.44 17.00 5.40 9.66 0.56 15.50 5.50 9.97 0.55 16.00 6.30 9.87 0.64 08:00 15.00 3.20 10.08 0.32 16.50 5.30 9.76 0.54 08:00 15.00 2.20 10.08 0.22 14.50 3.80 10.19 0.37 08:10 15.00 3.20 10.08 0.32 15.00 6.50 10.08 0.64 08:05 14.50 7.00 10.19 0.69 15.50 6.00 9.97 0.60 08:05 14.50 4.80 10.19 0.47 16.00 3.00 9.87 0.30 08:20 14.00 6.40 10.30 0.62 15.50 6.20 9.97 0.62 08:15 12.00 4.90 10.77 0.45 11.00 7.20 11.02 0.65 08:15 12.00 8.00 10.77 0.74 13.00 6.20 10.53 0.59 Table 6: Morehead City Instream Monitoring Data (Summer) Obs date Maximum Minimum Average time up up up up down down down down temp (c) DO DO sat % sat temp (c) DO DO sat % sat 27.00 8.00 10.77 0.88 28.00 7.20 11.02 0.83 12.00 0.50 7.97 0.06 11.00 1.30 7.83 0.15 22.13 3.26 8.77 0.37 22.79 4.12 8.66 0.47 75th %-tile temperature upstream - 25 C Upstream linity - 25 -> Chlorinity - 13.8 DO Saturation - 7.083 mg/1 80% Saturation - (0.8)(7.083)-5.67 mg/1 • TABLE 3-2. SOLUBILITY OF OXYGEN IN WATER EXPOSED TO WATER -SATURATED AIR AT 1.000 ATMOSPHERIC PRESSURE (APHA, 1985) Temp. 1n eC 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0 16.0 17.0 18.0 19.0. 20.0 21.0 22.0 23.0 24.0 25.0 26.0 27.0 28.0 29.0 30.0 31.0 32.0 33.0 34.0 35.0 36.0 37.0 38.0 39.0 40.0 0.0 5.0 Chlorinity. PA 10.0 15.0 20.0 25.0, Dissolved Oxygen. m//1 Difference per 0.1 ppt Chlorinity 14.621 13.728 12.888 12.097 11.355 10.657 0.016 14.216 13.356 12.545 11.783 11.066 10.392 0.01S 13.829 13.000 12.218 11.483 10.790 10.139 0.015 13.460 12.660 11.906 11.19S 10.526 9.897 0.014 13.107 12.335 11.607 10.920 10.273 9.664 .0.014 12.770 12.024 11.320 10.656 10.031 9.441 0.013 12.447 11.727 11.046 10.404 9.799 9.228 0.013 12.139 11.442 10.783 10.162 9.576 9.023 0.012 11.843 11.169 10.531 9.930 9.362 8.826 0.012 11.559 10.907 10.290 9.707 9.156 8.636 0.012 11.288 10.656 10.058 9.493. 8.959 8.454 0.011 11.027 10.415 9.835 9.287 8.769 8.279 0.011 10.777 10.183 9.621 9.089 8.586 8.111 0.011 10.537 9.961 9.416 8.899 8.411 7.949 0.010 10.306 9.74: 9.218 8.716 8.242 7.792 0.010 10.084 9.541 9.027 8.540 8.079 7.642 0.010 9.870 9.344 8.844 8.370 7.922 7.496 0.009 9.665 9.153 8.667 8.207 7.770 7.356 0.009 9.467 8.969 8.497 8.049 7.624 7.221 0.009 9.276 8.792 8.333 7.896 7.483 7.090 0.009 9.092 8.621 8.174 7.749 7.346 6.964 0.009 8.915 8.456 8.021 7.607 7.214 6.842 0.008 8.743 8.297 7.873 7.470 7.087 6.723 0.008 8.578 8.143 7.730 7.337 6.963 6.609 0.008 8.418 7.994 7.591 7.208 6.844 6.498 0.008 8.263 7.850 7.457 7.083 6.728 6.390 0.007 8.113 7.711 7.327 6.962 6.615 5.285 0.007 7.968 '7.575 7.201 6.845 6.506 6.184 0.007 7.827 7.444 7.079 6.731 6.400 6.085 0.007 7.691 7.317 6.961 6.621 6.297 5.990 0.007 7.559 7.194 6.845 6.513 6.197 5.896 0.007 7.430 7.073 6.733 6.409 6.100 5.806 0.006 7.305 6.957 6.624 6.307 6.005 5.717 0.006 7.183 6.843 6.518 6.208 5.912 5.631 0.006 7.065 6.732 6.415 6.111 5.822 5.546 0.006 6.950 6.624 6.314 6.017 5.734 5.464 0.006 6.837 6.519 6.215 5.925 5.648 5.384 0.006 6.727 6.416 6.119 5.835 5.564 5.305 0.006 6.620 6.316 6.025 5.747 5.481 5.228 0.006 6.515 6.217 5.932 5.660 5.400 5.152 0.005 6.412 6.121 5.842 5.576 5.321 5.078 0.005 DEFINITION OF SALINITY Although salinity has been traditionally defined as the total solids in water after all carbonates have been converted to oxides, all bromide and iodide have been replaced by chloride, and all organic matter has been oxidized, the new scale used to define salinity is based on the electrical conductivity of seawater relative to a specified solution of KC1 and M(i(UNESCO, 1981). The scale is dimensionless and the traditional dimensions of parts per .thousand .e., mg/g of solution) no longer applies! DEFINITION OF IIMORINITY Chlorinity is now defined In relation to salinity as.follows: Salinity • 1.80655 (Chlorinity) Although chlorinity is not equivalent to chloride concentration, the factor for translating a chloride deterid nation in seawater to include bromide, for example, is only 1.0045 based on the molecular weights and the relative amounts of the two ions. Therefore, for practical purposes, chloride (in mg/g of solution) is nearly equal to chlorinity in seawater. For wastewater, a knowledge of the ions responsible for the solution's electrical conductivity is necessary to correct for the ions impact on oxygen solubility and use of the tabular value or the equation is inappropriate less the relative composition of the wastewater is•slmllar to seawater. Table 7: Chlorinity Source: Bowie et al., 1985 93 Table 8 CALICO CR. CHEMICAL DATA STATION DATE TIME BOD5 TOT.S TSS NH3 TKN NO2+NO3 TOT.P (mq/I) (mg/I) (mq/I) (mg/I) (mg/I) (mg/I) (mq/I) C-1 9/20/88 1345 0.23 2.7 0.39 0.48 C-1 I9/20/88 1820 0.02 1.1 0.09 0.41 MC-2.. (eft.) • 1 200-1 200 1 3 ' 200 3 4.60 Giu 6.10 2.30 I C-3 19/20/88 1355 0.01 1.1 <0.01 0.22 C-3 ' 9/20/88 1 830 0.04 1.0 0.10 0.34 C-5 9/20/88 1405 0.02 0.7 <0.01 0.13 C-5 ; 9/20/88 1 835 0.03 0.7 0.09 0.19 C-6 9/20/88 1420 0.01 0.6 0.01 0.10 0-6 9/20/88 1845 0.01 0.4 0.02 0.12 I C-7 :9/20/88 1435 0.05 0.6 0.01 0.08 0-7 I9/20/88 1855 0.02 0.4 <0.01 0.09 NEW-1 (C-10)' 9/20/88 1 500 0.01 0.4 <0.01 0.02 ' 24 hour composite 9.20-21/88 1200--12Cv Appendix I Cross -sectional Measurements of Calico Creek August, 1981 Calico Creek Cross -sections 8-27-81 sX-ection #1. Time 0820 . 2 Auea 306ft. Near StaLimi. C-i 1— Width (ft.) 4 3i0 10 60 110 120 2 1:0 13 5? 7p sp — — — D (f t.)2_ 3- 4— Water Level at X-section Bo..ylm Profile X-Section #2 Time 0835 , it I ea 34Sft: Near S'Latiou C-3 10 20 30 40 5p 6t) 4- 108 I i d e — Tide Water Level at X-sec.tio!: Bottom ProCile - —Tide X-Saoclon #3 u Time 0840 2 Area 156017c. Calico Czaab Cross -sections 8-27_81 Width ([t.) V 100 000 000 Near Station C-4 1-- D e Q � (f t^) o— o— *-- 400 soo aou __________l|[):.!`?t'|, Bottom Pr(�:*ile Wn'tcr Lev�! lona Tide X-3mcLioo 04 o^- -rime 0846 Z Area 1.054fc. Nu^c Station C~5 1— D e 300 | Soo ( � ( � [t ) o . -~ m -�- Bottom Profile ^_ 60m 11J/,11'[iJc Water Level. at X-oeucion Cal|uo Ccmuk Cruay-uuL;Llunm 8-27-*i Wld'b ([t./ o 100 000 000 -~ 400 eoo 000 | � \ ___illgh TLde X-Section #5 n Wel*er �avui Iime 0854 2 aL X-amccioo Area 1572ft. Moar Station C-6 a- 4_ o / Bottom pr�.iLo — -Low. 7ide �oo�� 000 ' | (-Smuc1uo 0b o_ 'Lme OVi0 ' 2 �cea 254�[L. �euc ScuLLuu C-7 ,- - ([L^) o o_ *~ 000 400 soo onn zno oo» ---------~--- ,h Tide -` -' Duccom �zu�iie ^ ^ k�.ILuI* Level ,It X-mmutiun l`/J":