4.1.2 - Baseline Low Flow Water Quality

One of the main objectives of this study was to evaluate the current water quality of Strawberry Creek during low flow conditions. Reliable baseline data is essential to document future changes in the environmental quality of Strawberry Creek and to assess the effects of urban runoff during wet weather periods. The creek's waste assimilative capacity is generally at its lowest during the extended low streamflow period because dilution cannot be counted upon to dissipate wastes. Strawberry Creek is therefore most vulnerable to point and non-point sources of pollution at this time. Baseline data also serves as the basis for water quality management recommendations. 

Baseline data was collected monthly from May through August of 1987. Grab water samples for chemical and bacteriological analysis as well as dissolved oxygen determination were collected at six locations on both the North and South Forks. Grab samples were taken at the middle of the stream channels at mid-depth. Grab samples for heavy metals analysis were collected during the July and August sampling rounds. Metals samples were preserved with concentrated nitric acid. All samples were kept cold in a cooler immediately following collection and delivered within five hours to the California Department of Health Services Sanitation and Radiation Laboratory in Berkeley for chemical and bacteriological analyses according to the procedures set forth in the APHA Standard Methods for the Examination of Water and Wastewater (1985). These methods are summarized in Table 10.

Dissolved oxygen determinations were made by the author using the Winkler iodometric titration method. In conjunction with the water samples, streamflow was determined by measuring water velocity with a Teledyne Gurley Mcxiel 625 Pygmy current meter and multiplying the velocity by the cross-sectional area of the flowing water. Where low flow conditions did not permit use of the Pygmy meter, bucket flow or time of travel (float) measurements of stream velocity were performed. A summary of streamflow measurements is presented in Table 5.

Sampling locations are shown on Figure 10. Stations #1-3 are located on the South Fork, whereas stations #4-6 are on the North Fork. Station #1, located above the retention dam, receives drainage from the upper canyon areas via Hamilton Creek as well as Strawberry Creek and its tributaries. The majority of the flow is comprised of overflow from a groundwater pumping well and EBMUD water used to augment flow in the Botanical Garden. A smaller portion is natural baseflow from Hamilton Creek which drains upper Strawberry Canyon. 

Station #2 is located on the South Fork at the Faculty Club, downstream of the confluence of the Big and Little Inch bypass culverts. Water quality at this location is influenced by Chicken Creek drainage from LBL, local drainage from the former Poultry Research area, as well as the fact that the creek is routed underground for approximately three-fourths of a mile. In addition, any discharges from the Haas pool complex, Memorial Stadium, Cowell Hospital, or the Greek Theater would be evident here.

The last station on the South Fork (#3) is located in the Eucalyptus Grove just upstream of its confluence with the North Fork. Central campus point and non-point source discharges will greatly affect the water quality at this station. Changes in the physical, chemical, and bacteriological parameters between the sampling stations can be examined to identify possible sources of pollution and evaluate their impacts.

Station #4 is located on the North Fork above Highland Avenue. Most of the dry weather stream.flow here originates from groundwater dewatering wells and drains around the Lawrence Berkeley Laboratory (LBL) complex.

Station #5 is located at the North Fork's entrance onto the central campus from the city culvert Dry weather water quality here is influenced by drainage from the N orthside district of the city. Minor flows from the upper Euclid Avenue storm drain system and Etcheverry Hall also enter the city tunnel.

The last station on the North Fork (#6) is located in the Eucalyptus Grove just upstream of its confluence with the South Fork. The low-flow water quality here is influenced by discharges and runoff from the central campus. The cross-campus culvert, a major campus storm drain system, empties into the North Fork just above the University Drive vehicle bridge. As in the South Fork, changes in water quality can be examined in terms of the different activities along the creek. The sampling sites were designed to isolate different areas of the North Fork subwatershed in order to assess the water quality impacts and pollution sources in different areas.

Water quality parameters will be analyzed in terms of apparent trends and threshold levels. The concentrations of various water quality constituents will also be compared to USGS analyses of other East Bay creeks as well as ABAG data for Bay area creeks at large. Tables summarizing these low flow comparative water quality data can be found in Appendix B. Historical low flow studies of the creek will also be considered for comparison. The baseline data will also be discussed in terms of R WQCB objectives for surface waters where applicable. Baseline water quality data is presented in Appendix A. RWQCB water quality standards are given in Table 11.

Dissolved oxygen refers to the uncombined oxygen in solution which is available to aquatic organisms for respiration. Solubility of oxygen in water is primarily a function of water temperature. Solubility decreases from 11.3 mg/1 at 10° C to 9.2 mg/1 at 200 C. Summer low flow periods are the most critical times for aquatic life in terms of oxygen levels because the water temperature is warmest, resulting in lower oxygen solubilities at the same time metabolic rates (oxygen demand) of aqqatic organisms are at their highest. The ability of a stream to assimilate organic materials (waste assimilative capacity) is also dependent upon the amount of dissolved oxygen present in the water. Creeks may assimilate more biodegradable organic material without significant water quality degradation if hydraulic reaeration rates are high.

Dissolved oxygen (D.O.) concentrations were quite high in both forks of Strawberry Creek. Concentrations decreased slightly in the downstream reaches of both forks. The North Fork had slightly lower overall D.O. concentrations than the South Fork. D.O. was often supersaturated at the headwater stations of both forks and was at or near saturation downstream.

The D.O. concentrations measured in Strawberry Creek were more than adequate to support the aquatic organisms indigenous to the creek and could even support salmonid fisheries. The D.O. exceeded the RWQCB minimum criteria for surface waters as well as the D.O. concentrations measured in other East Bay creeks. The D.O. also equalled or exceeded the concentrations measured in past studies of Strawberry Creek.

The supersaturated D.O. concentrations observed in the creek are probably due to physical aeration caused by the creek cascading down steep gradients over numerous check dams, entering drop inlets, and splashing out of culverts. Biological interactions do not appear to be a factor in the high D.O levels. The slight decline in D.O. downstream is insignificant and due to a combination of factors such as increased water temperature, leveling off of stream gradients, and a slight increase in organic loading. The high D.O. saturations indicate a low level of biodegradable organic wastes.

As previously discussed, water temperature is the main factor controlling the solubility of oxygen. The creek's assimilative capacity is therefore strongly influenced by water temperature. Water temperature also influences the rate of biological activity and affects the physical properties of water such as density and viscosity.

Strawberry Creek water temperatures increased slightly downstream compared to the canyon headwater stations. The South Fork was slightly cooler than theNorth Fork. Over the summer months, a slight warming trend was observed at all stations. Temperatures at the headwater stations ranged from 11.0 -15.6° C, whereas the downstream temperatures ranged from 14.2-18.6° Cover the summer. The largest consistent temperature change between consecutive stations was observed in the North Fork at downstream stations #5 and #6. Temperatures at station #6 were 1.5-4.4° C higher than at station #5. This was probably due in great part to the input of effluent from the cross-campus culvert (Point #92) at University Drive which discharged a large volume of water averaging 21.0° Cover the summer months. The stream.flow of the North Fork was approximately doubled by the flow from this culvert over the summer. 

Water temperatures in Strawberry Creek were adequate to support the indigenous aquatic life and could even support cold water (< 20° C) fisheries. The apparent elevation of ambient water temperature by the cross-campus culvert discharge could have a deleterious impact on the suitability of downstream waters for aquatic habitat, but the magnitude of temperature elevation generally did not exceed the RWQCB criterion which prohibits a direct elevation of more than 5° F.

Biochemical oxygen demand (BOD) is a measure of the amount of oxygen required by bacteria to stabilize decomposable_ organic matter under aerobic conditions. Through recurrent use, the five day BOD test has become accepted as the standard. Approximately 70-80% of the ultimate BOD, which is exerted over the perioo of a month or more, is exerted within five days. BOD is used to determine the pollutional strength of waters in terms of the oxygen required to decompose organic matter. BOD is important only insofar as it produces deoxygenation resulting in detrimental anaerobic conditions.

The BOD5 in both forks of Strawberry Creek was low. The South Fork had slightly lower downstream
BOD5 values than the North Fork. Slight increases in BOD5 were observed at North Fork stations #5 and #6, suggesting organic loading from the North Berkeley city tunnel area and point source loading on the central campus. Hilgard Hall sanitary sewage is probably responsible for the central campus loading (see Section 4.3.1).

The BOD5 measured in the creek was lower than levels observed in other East Bay creeks. It does not appear that organic contamination of the creek is a significant problem. The low BOD5 concentrations correlate with the high dissolved oxygen concentrations observed in the creek.

Chemical oxygen demand (COD) measures the amount of oxygen required for the chemical oxidation of organic matter. Some types of organic materials such as cellulose are biologically resistant to bacterial decomposition, but almost all organic compounds can be chemically oxidized. Since some organic material in any water is non-biooegradable, COD is almost always higher than BOD. Chemical oxidation of 95-100% of organic material is achieved by this test.

COD concentrations on the average were about three times higher than the BOD5 levels in both forks of Strawberry Creek. COD tended to increase downstream in both forks, but the COD levels were similar in each fork. COD concentrations observed in the creek were much lower than those found in other East Bay creeks. It appears that most of the organic loading in the creek is of a non-biodegradable nature and does not have a significant effect on the water quality of Strawberry Creek.

pH is a measure of hydrogen ion activity in water as measured on an inverse logarithmic scale ranging from 0-14. pH< 7.0 indicates higher hydrogen ion concentrations, or acidic conditions. Natural waters exhibit a wide range of pH depending on their chemical and biological characteristics. pH has a direct effect on aquatic organisms and may also indirectly affect aquatic life by increasing the toxicities of certain pollutants such as ammonia and various metals under acidic conditions.

The pH of Strawberry Creek was slightly alkaline, averaging 8.1 in the South Fork and 8.0 in the North Fork. The pH tended to decrease slightly downstream in the South Fork and noticeably decreased downstream in the North Fork. The pH of the creek was similar to that observed in past low flow studies and was higher than the average pH found in other East Bay creeks.

The pH range of Strawberry Creek provides a suitable environment for most aquatic life. The lowered pH downstream in the North Fork approximates the pH of EB MUD water (7. 7). This suggests that the decreased pH is due to dilution of the creek with point source effluent from the central campuespecially the cross-campus culvert. R WQCB standards do not allow the ambient pH level to be changed by more than 0.5 units. pH consistently decreased by 0.4 units between North Fork stations #5 and #6. 

Alkalinity is commonly defined as the capacity of solutes in water to neutralize acid. In natural waters alkalinity is primarily caused by bicarbonates-carbonates and, to a lesser extent, by hydroxides, borates, silicates, phosphates, and organic ligands. Alkalinity is a practical measure of the buffering capacity of a water body which is important because of the direct and indirect effects of pH on aquatic organisms.

Similar trends as observed with pH were found in the alkalinity o(Strawberry Creek . On the average, alkalinity decreased from 140 to 106 mg/1 downstream in the South Fork, whereas it decreased from 164 to 86 mg/I in the North Fork. The significant drop in the North Fork occurred along the central campus reach of the creek. This appears to be due to dilution of the creek with effluent similar to EBMUD water. EBMUD water has an alkalinity of only 22 mg/1.

The alkalinity of Strawberry Creek was equal to or generally less than the alkalinity found in other East Bay creeks. The significant reduction in the buffering capacity of the North Fork could have adverse effects on aquatic life, but the alkalinity was still adequte to support a diversified aquatic community.

Hardness is a measure of the polyvalent metallic ions dissolved in water. In freshwater, calcium and magnesium are the primary ions responsible for hardness, but iron, manganese, and other trace elements also contribute. Hardness is directly related to the total dissolved solids content of a water body. The toxicity of many metals decreases as carbonate hardness increases. Aquatic organisms may also be affected by the specific ions causing hardness.

Hardness follows the same trends observed with pH and alkalinity, based on the results of a single sampling round (8/19/87). Similar decreasing trends were found in both the North and South Forks. Hardness dropped significantly between the central campus sampling stations on both forks. Hardness ranged from 92-170 mg/1 in the North Fork and 100-156 mg/I in the South Fork.

Strawberry Creek can be considered to be "moderately hard to hard" in terms of hardness. In general, the toxicity of most heavy metals in the creek would be lessened if the creek had "softer" water. The decrease in hardness on the central campus can again be attributed to dilution with effluent similar to straight EBMUD water which has a hardness of 24 mg/I.

Conductivity is the measure of the ability of water to conduct electrical current. It is related to the number and types of ions in solution as well as the dissolved solids content of the water.

South Fork conductivity decreased consistently downstream, averaging 382 umhos/cm in the canyon and 326 umhos/crn at the Eucalyptus Grove. On the other hand, conductivity averaged about 411 umhos/cm in the North Fork until it flowed through the central campus where it dropped to an average of 238 umhos/cm. The conductivity of Strawberry Creek was generally less than what was observed in other Bay area creeks. The significant drop in conductivity of the North Fork can be explained by dilution with point source effluent similar to EBMUD water which has a conductivity of 63 umhos/cm.

Dissolved solids are those that remain in solution after filtration. They are comprised of inorganic ions such as sodium, carbonates, sulfates, nitrates, potassium, calcium, and magnesium as well as small amounts of organic matter such as humic acids, and dissolved gases. Dissolved solids concentrations generally range from 55-75% of the total conductivity. Dissolved materials may reduce the toxicity of certain heavy metals and organic compounds.

Total dissolved solids (TDS) content of Strawberry Creek followed similar trends as observed with hardness and conductivity. In the South Fork, a steadily decreasing trend was apparent whereas an abrupt decline occurred in the North Fork on the central campus. TDS concentrations were similar in the upstream stations of both forks. Overall, the TDS content of the creek is fairly low compared to USGS and ABAG data for Bay area creeks. The sharp decrease in TDS in the North Fork can again be attributed to the addition of a large volume of point source effluent similar to EBMUD water which is very low (46 mg/1) in TDS. 

In contrast to TDS, suspended solids consist of organic and inorganic particulate matter which floats on the surface or is held in suspension in the water. Suspended solids are related to turbidity and may interfere with recreational uses and affect aesthetics. If the particulate matter is of organic origin, it may exert a high BOD. Solids may also smother benthic macroinvertebrates and detract from aquatic habitat in general.

Total suspended solids (TSS) were low in both forks of Strawberry Creek but tended to increase downstream. TSS were slightly higher in the North than in the South Fork. Average TSS content in the creek was generally lower than in other Bay area creeks and also lower than historically reported levels. The low suspended solids concentrations should not adversely affect aquatic organisms or beneficial uses of Strawberry Creek. It appears that the suspended material was of inorganic origin because the BOD and COD levels were low.

Turbidity is a measure of water clarity and is related to the TSS content. It is caused by a wide variety of suspended and colloidal matter that diminish light penetration into the water. Like TSS, turbidity interferes with recreational uses as well as aesthetic enjoyment of water bodies and can have an adverse effect on aquatic organisms.

Turbidity exhibited the same trends as suspended solids in Strawberry Creek. Similar low levels which tended to increase downstream were observed in both forks. These concentrations were generally lower than those reported for other Bay area creeks and lower than previously observed levels.

Color is due primarily to complex organic compounds originating from the decomposition of organic matter. It is usually not harmful to aquatic life, but may restrict light penetration, resulting in effects similar to high turbidity. Surface waters may also appear highly colored because of suspended material.

Overall, the color of Strawberry Creek was very low. No trends were observed in the South Fork, but color increased downstream in the North Fork. The low color content suggests a low organic content which correlates with the BOD and COD analyses. In general, the low color of the creek should not adversely affect any beneficial uses or organisms.

Chlorides occur in all natural waters in widely varying concentrations depending on soils and geology as well as proximity to the ocean. It is a conservative water property that fluctuates very little seasonally and only slowly over time. Chlorides are quite soluble so they may pass through pervious soils and rocks for great distances without diminution. Sewage is the primary cultural source of chlorides.

The chloride content of Strawberry Creek was fairly low. Chloride levels in both forks were similar. The South Fork levels were fairly consistent, but the North Fork exhibited a significant decrease in chloride content on the central campus. The chloride concentrations in the creek were similar to levels found in other East Bay creeks. The decline in chlorides in the North Fork can be explained by dilution from effluent similar to EBMUD water which is quite low (3 mg/1) in chloride content.

Oil and grease includes thousands of organic compounds with varying physical, chemical, and toxicological properties. Grease consists of a mixture of hydrocarbons, esters, oils, fats, waxes, and free fatty acids. These compounds may.or may not be volatile, soluble, or persistent. Both petroleum and non-petroleum oils cause harmful effects by forming a sheen, film, or discoloration on the water surface. Oils may also be emulsified in the water column, solubilized, or settle to the bottom as sludge. Animal and vegetable oils are generally non-toxic to humans and aquatic life.

Oil and grease concentrations were generally low in Strawberry Creek. Levels in both forks were consistently quite low except for moderately high concentrations which were observed in the North Fork at stations #4 and #6 on July 22, 1987. Sources of this oil and grease would have been LBL and point source effluent from the central campus. Average oil and grease concentrations were generally lower than levels observed in other Bay area creeks. 

Nutrients are substances which are essential for the growth and reprcxiuction of living organisms. In aquatic habitats, algae and vascular plants depend on dissolved nitrogen and phosphorus compounds as primary nutrients. Excessive nutrient loading of a water bcxiy increases the net productivity of aquatic ecosystems resulting in eutrophication. Eutrophication is manifested by excessive weed or algal growth which can have a deleterious effect on the beneficial uses of a water body. Decomposing vegetation also exerts a high oxygen demand on the water which adversely affects aquatic habitat.

Nitrogenous compounds exist in a variety of forms such as particulate matter, inorganic ions, soluble organic substances, and cellular components. Oxidation and reduction of these compounds is closely related to the metabolic processes of many types of microorganisms. The bacterial decomposition of nitrogenous matter is known as nitrification and is carried out through a fixed sequence of ox;idation reactions. Organic nitrogen is oxidized to ammonia which is converted to nitrite which is rapidly oxidized to nitrate. Organic nitrogen in the form of protein, urea, or amino acids occurs in waters containing organic wastes such as sewage. By assessing the relative amounts of various nitrogenous compounds present, the extent and timing of any organic pollution can be determined.

Total Kjeldahl nitrogen (TKN) includes both organic nitrogen and ammonia, and is a measure of the potential for oxygen consumption of the nitrogenous matter .in water. It is also a reliable indicator of recent sewage contamination. TKN concentrations in both forks of Strawberry Creek were low. South Fork levels were consistently low, whereas a small increase in TKN concentrations were observed downstream in the North Fork on the central campus. The TKN concentrations found in the creek were generally lower than those reported for other East Bay creeks. Small amounts of organic wastes appear to be emanating from the North Berkeley city tunnel and from a central campus source, probably Hilgard Hall (see Section 4.3.1).

Ammonia is the initial decomposition prcxiuct of organic nitrogen. It may be used directly by plants with the excess oxidized to nitrite and ultimately nitrate. Un-ionized ammonia (NH3) is the principal toxic form of ammonia to many aquatic organisms. Ammonia is also important because it exerts high oxygen and chemical demands on a water body. Surface waters with high concentrations of organic and ammonia nitrogen are indicative of recent organic pollution and may pose a health hazard.

Average ammonia concentrations in both forks of Strawberry Creek were generally low, ranging from <0.04-0.13 mg/1 in the South Fork, and from 0.06-0.22 mg/1 in the North Fork. Concentrations were consistently low in the South Fork, whereas a slight increase in ammonia levels was observed downstream in the North Fork. This coincides with the results of the TKN analyses. The ammonia concentrations found in Strawberry Creek were in the range of previously reported levels and similar to other East Bay creek concentrations. A comparison of the TKN and ammonia analyses for the downstream reaches of the North Fork reveals that most of the relatively low TKN content is comprised of organic nitrogen rather than ammonia. This suggests very recent organic loading.

Nitrate nitrogen is the end prcx:luct of the aerobic decomposition of organic nitrogenous matter. Nitrate is the most directly available form of nitrogen for uptake by vascular aquatic plants and algae. Therefore, its presence often increases the net productivity of aquatic systems, contributing to eutrophication. Nitrate may be indicative of previous pollution that has already undergone the natural oxidation processes of self-purification •. Nitrate is seldom abundant in natural surface waters.

Nitrate concentrations were consistently high in the South Fork and very high in the North Fork, especially downstream. South Fork average nitrate levels ranged from 1.7-2.0 mg/1, whereas average North Fork concentrations ranged from 2.2-4.7 mg/1. These levels were generally higher than the nitrate concentrations found in other East Bay creeks and similar to previously reported levels. The nitrate concentrations in Strawberry Creek are indicative of eutrophic conditions. This appears to be due to the presence of nitrogenous matter of natural origin from the canyons which is compounded by organic loading downstream, especially in the North Fork. 

Algae and vascular aquatic plants also rely on phosphorus as an essential nutrient Phosphorus is frequently the key limiting nutrient in the process of eutrophication and is usually easier than nitrogenous compounds to control. Phosphorus may be present in dissolved, colloidal, or particulate states as orthophosphate, polyphosphate, or as organic compounds.

Average total phosphorus concentrations were consistently high in the South Fork and also high downstream in the North Fork. Average phosphorus ranged from 20-<0.26 mg/1 in South Fork, whereas average North Fork levels ranged from 0.10-0.50 mg/1. The highest concentrations were consistently measured at the North Gate sampling station. The phosphorus levels found in the creek are indicative of eutrophic conditions. The source of the high phosphorus at North Gate could be sewage or decaying urban runoff material in the storm drain system. Total phosphorus concentrations in Strawberry Creek are similar to levels reported by USGS for other East Bay creeks.

Total coliform bacteria counts measure the presence of both soil-vegetation bacteria and intestinal bacteria from warm-blooded animals, including man. Coliform bacteria are not normally considered disease organisms and are comprised of the genera Eschericia, Serratia, Erwinia, Klebsiella, and Enterobacteria. Coliforms are used as indicators of sanitary pollution because they are inexpensively detected by relatively simple test procedures and are non-pathogenic. These water-borne organisms accumulate in bottom sediments as they settle out of the water column.

Total coliform concentrations in Strawberry Creek were generally within expected naturally-occurring ranges. Coliform levels increased downstream in both forks, especially the North Fork. These bacteria concentrations were within the range of previously reported results and similar to the levels found in Castro Valley Creek in Hayward. In order to determine the sources of these coliform bacteria, fecal bacterial analyses were also performed.

Although not a serious health hazard themselves, fecal coliform and fecal streptococcus bacteria are the primary indicators of fecal contamination. These bacteria are found exclusively in the intestinal tract of warm-blooded animals including man. Their presence indicates that other potentially pathogenic bacterial, viral, protozoan, or fungal species may also be present. Greater numbers of these bacteria generally indicate an increased health risk. Fecal streptococci indicate fresh pollution because they quickly die off outside their host. Fecal strep bacteria are much more abundant in animals than in man.

The ratios between concentrations of fecal coliform and fecal streptococci bacteria are commonly used to differentiate between human and animal fecal contamination. Human wastes will generally have a fecal coliform : fecal streptococcus ratio of greater than 4.0 (EPA, 1980).

Fecal coliform concentrations were low at the canyon sampling stations in both forks but increased to high levels downstream, especially in the North Fork. Average fecal coliform concentrations ranged from 260-> 11,000/100 ml in the South Fork, whereas average North Fork levels ranged from 825->34,500/100 ml. These fecal coliform concentrations violate the RWQCB criterion for surface waters (mean< 2,000/100 ml).

Average fecal streptococcus concentrations in the South Fork ranged from 1,275-11,025/100 ml, whereas average levels in the North Fork ranged from 4,475->51,750/100 ml. Both fecal coliform and fecal streptococcus bacteria concentrations were generally higher than those observed in other East Bay creeks.

Fecal coliform : fecal streptococcus ratios indicate probable sewage contamination in the North Fork at North Gate, and to a lesser extent downstream at the Eucalyptus Grove in both forks. The FC: FS ratios at North Gate ranged from 1.0 to 20.0, whereas the ratios in both forks at the Grove generally ranged from 1.0 to 3.2. Sewage contamination of the North Fork from Hilgard Hall explains the elevated downstream bacteria counts in that fork, and EH&S/DOFM is currently investigating the possibility of sewage contamination from Point #68 downstream in the South Fork. 

Additional fecal bacteria samples were taken on August 19, 1987 in an attempt to further define the sources and types of bacterial contamination emanating from the city storm drain tunnel under the Northside district. Figure 11 shows the specific sampling locations and the results are presented in Table 12. FC:FS ratios indicated abundant animal fecal material at that time rather than sewage contamination. This may indicate an intermittent sewage problem at this location because FC:FS ratios at most other times indicated sewage contamination. Fecal coliform counts increased significantly downstream of the old creek tunnel south of Euclid Avenue (Figure 11). This section of old tunnel is a suspect area for sewage infiltration or illegal connections. The high fecal streptococcus concentrations suggest animal activity and was confirmed by the observation of several raccoons in the tunnel. Berkeley DPW Engineering Department is currently investigating possible sources of sewage contamination in the North Fork tunnel.

Heavy metals are present in trace quantities in the natural environment and also originate from a wide variety of sources in the urban environment. Metals are toxic to aquatic organisms when present in sufficient concentrations. Toxicity of various metals is dependent upon a variety of environmental factors including chemical state (speciation) of the metal, chemical properties of the water such as pH and hardness, and synergistic/antagonistic effects. Metals may bioaccumulate in aquatic organisms and often concentrate in bottom sediments. Metals content can limit the beneficial uses of a water body.

In general, trace metals concentrations in both forks of Strawberry Creek were low compared to natural background levels found in California rivers (Table 13), and concentrations observed in other East Bay creeks. Average metals levels were similar in both forks and were generally higher downstream compared to the canyon sampling locations. Elevated mercury concentrations were found at different times in the South Fork at Strawberry Canyon and also in the North Fork at North Gate. An elevated lead concentration was also observed in the South Fork at the Eucalyptus Grove. Metals levels in Strawberry Creek were generally within the RWQCB standards for surface waters (Table 14).

Beta radiation is the emission of electrons from the nucleus of a radioactive substance. It is the form of radiation exhibited by the majority of radioactive materials used in research at the University. Beta radiation is readily detectable using liquid scintillation counting techniques and can be used to determine the quantity of radioactive material in a water sample.

Liquid scintillation counts were performed by EH&S personnel on grab water samples in conjunction with the July and August water quality sampling rounds of Strawberry Creek. The analyses showed no beta radiation in excess of naturally occurring background levels. This indicated that no significant radioactive contamination was present in the creek at the time of sampling.

In summary, the water quality of Strawberry Creek is fairly good in the canyon areas, but has been degraded in the urbanized downstream reaches by point source effluent and bacterial contamination. The dissolved oxygen concentrations in the creek are high and the oxygen demand levels are coincidentally low. A significant alteration in pH, alkalinity, hardness, conductivity, and dissolved solids content occurs in the North Fork on the central campus because of point source dilution of the natural baseflow. Nutrients in the form of nitrate and phosphorus are high and indicate eutrophic conditions. Fecal bacteria concentrations were high in the downstream reaches of the creek, especially in the North Fork. This may pose a public health hazard. Trace metals in Strawberry Creek were generally low.