A walking survey of both forks of Strawberry Creek on the central campus identified over 100 pipes on its banks (Table 20). An effort was made using DOFM underground utilities maps and field checking to determine the sources of these pipes. The locations of these pipes are shown on Figure 15. It was found that only about a dozen of these pipes flow continuously. Physical data on this continuously flowing effluent based on repeated field observations is presented in Table 21.
Of the dozen pipes that flow continuously, eight were targeted for chemical analyses based on their flow characteristics and sources. Generally the pipes with the highest flows and largest subcatchment areas, or those which physically presented signs of possible pollution were chosen for water quality sampling. Chemical analyses of the targeted point sources was conducted once during the summer (June-July), and again while full classes were in session (November-December) in order to assess the chemical composition of the effluent under different campus operating conditions. The cross-campus culvert (#92) was sampled twice during the summer because of its extensive drainage area and large volume of effluent.
An ISCO model 2700 automatic water sampler was used to obtain 24 hour composite samples of the major point sources. The sampler was programmed to extract a 100 ml. aliquot from the flowing pipes every 30 minutes for 24 hours. The composite water sample was kept cold by surrounding the sample bottle held inside the ISCO sampler with ice packs.
The glass sample bottle was previously rinsed out with the effluent to be sampled to remove any foreign residue that might have been present. The composite water samples were placed in appropriate containers upon retrieval. Volatile organics vials used for the TOC analysis were preserved with sulfuric acid. All samples were kept refrigerated until delivered on ice to a state certified laboratory for chemical analysis. All samples were sent to the lab within four days of collection.
The composite water samples were analyzed for total organic carbon (TOC) and chemical oxygen demand
(COD) to assess total organics content. A semiquantitative ICP (inductively coupled plasma) scan for trace elements including many metals was also performed on the summer round of composite samples. Analyses of selected common heavy metals were performed on the November-December samples at lower detection limits than were possible with the ICP scan. Results of these analyses are presented in Table 22.
COD refers to the amount of oxygen required for the chemical oxidation of organic matter. Oxidation of >95% of organic compounds is achieved by this test (Std. Methods, 1985). COD is significant because the assimilation of large amounts of organic waste severely depletes the oxygen concentration of the receiving body, rendering it unsuitable for the existence of aquatic organisms. The COD concentrations of the point source effluent were consistently higher in November-December than during the summer sampling round. The COD levels of all the point sources tested during the summer were below the detection limit ( 1.0 mg/I) except for the Heating Plant (#106) effluent which was slightly elevated (11 mg/1). However, COD concentrations of the point source effluent ranged from 10-63 mg/I during the November-December sampling round. In general, COD levels were quite low during the summer and elevated in the fall. Specifically, the COD of effluent from point #68 was high ( 63 mg/1), whereas point sources #15 and #106 had elevated (29-31 mg/I) concentrations.
The organic carbon in wastewater is composed of a variety of organic compounds. Some of these compounds do not respond to the COD Jest, so TOC is a more direct expression of total organic carbon than COD. Both extractable organics and biogenic humic substances contribute to TOC (Std. Methods, 1985). However, TOC does not measure organically bound elements or inorganics that can contribute to the oxygen demand measured by COD, so TOC measurement does not replace COD analysis. The results of TOC analyses generally correlate with the trends observed with COD. TOC was low at all times in all the point source effluent except for point #68 which was high (26 mg/I) in November. From the results of the COD and TOC analyses it appeared that there was an intermittent non-volatile organic pollution problem at point source #68. This helped to prompt further investigation irito this storm line (see Section 4.3.1).
Metals may originate from a wide variety of sources in wastewater discharges. Metals content may limit the beneficial uses of a water body and may cause acute or chronic toxicity in aquatic organisms. Most of the trace metals and constituents analyzed during the summer sampling round were below the detection limits of the ICP scan in all the point source effluent tested. However, the lower detection limits used in the November-December metals analyses generally showed small but measurable amounts of cadmium, copper, iron, lead, and zinc. In general, the metals concentrations were within the Regional Water Quality Control Board's (RWQCB) standards for surface waters (Table 14).
All the metals concentrations in the point sources sampled were below the Maximum Contaminant Levels (MCLs) set forth in the National Primary and Secondary Drinking Water Regulations (Table B-1). Arsenic, cadmium, nickel, and silver concentrations were all at or below the chronic toxicity criteria for freshwater aquatic organisms recommended by the EPA (1986). Likewise, all the lead, mercury, zinc, and iron concentrations were at or below the acute toxicity criteria offered by the EPA.
Hexavalent chromium concentrations were below the detection limit (0.01 mg/1) of the analysis in all of the point source effluent except for point #68. A concentration of 0.03 mg/1 was measured here in November, which violates the RWQCB standards set at 0.011 and 0.016 mg/1 over a four day and one hour average, respectively. Even though the measured concentration is below the drinking water MCL (0.05 mg/1), it is in violation of surface water quality objectives.
Zinc concentrations were generally detectable in all of the point source effluent in trace amounts. The RWQCB standard of 0.058 mg/1 (over a 24 hour average) was exceeded at point sources #68 and #92 (0.11- 0.12 mg/1), although these levels are below both the EPA acute toxicity criterion for freshwater aquatic life (0.32 mg/1), and the SMCL for drinking water (5.0 mg/1).
The RWQCB surface water criterion for copper is 0.0092 mg/1 over a one hour average or 0.0065 mg/1 over a four day average. This objective was consistently exceeded in almost all of the point source effluents tested. However, the highest observed concentration (0.03 mg/1 at point sources #92 and #103) is still well below the SMCL for drinking water (1.0 mg/1).
Based on the physical and chemical data for the point sources investigated, it appears that most of the effluent is cooling water. Chemical analyses of EBMUD water supplied to the city of Berkeley are presented in Table B-1 for comparative purposes. The central campus point source effluent is chemically and physically quite similar to straight EBMUD water. Priority was given to investigating point source #68 because of the elevated hexavalent chromium and zinc concentrations observed there as well as the apparent organic contamination (see Section 4.3.1). Besides this point source, the cross-campus culvert (#92) generally had higher trace metal concentrations than the other point sources tested, so this warrants further investigation in the future. In addition, the Heating Plant (#106) poses a thermal pollution threat because of the high temperature and large volume of the effluent discharged into the creek above Oxford Street (see Section 4.3.1 ).
The point sources on central campus contribute a significant volume to the total low-flow stream discharge leaving the campus. North Fork point sources contribute an average of 0.14 cfs (63 gpm) to an average low flow streamflow of 0.28 cfs in that fork. This is approximately half of the total average summer baseflow of the North Fork. Point sources in the South Fork contribute an average of 0.29 cfs ( 130 gpm) or 50% of the average low-flow streamflow of 0.58 cfs. Therefore, during the course of this study, approximately 48% (0.43 cfs) of the total average summer baseflow (0.89 cfs) of Strawberry Creek was comprised of central campus point source effluent.