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HomeMy WebLinkAboutEIR 91-01; Rancho Santa Fe Rd Bridge Replacement Project; Environmental; 1997-03-24WATER QUALITY STUDY RANCHO SANTA FE ROAD BRTOGE REPLACEMENT PROJECT Submitted To: CITY OF CARLSBAD 2075 Las Palmas Drive Carlsbad, CA 92009-1576 ATTN: Doug Helming Prepared By: DUDEK & ASSOCIATES, INC. 605 Third Street Encinitas, CA 92024 ATTN: GailMasutani March 24, 1997 TABLE OF CONTENTS Page No. LIST OF FIGURES i LIST OF TABLES i 1.0 PURPOSE OF REPORT 1 2.0 PROPOSED PROJECT 2 3.0 HYDROLOGIC STUDY AREA 4 4.0 EXISTING WATER QUALITY 6 5.0 ENVIRONMENTAL EVALUATION 12 6.0 DISCUSSION 17 6.1 Surface Water 17 6.2 Groundwater 17 7.0 CONCLUSIONS AND RECOMMENDATIONS 18 8.0 REFERENCES 19 APPENDIX LIST OF FIGURES Figure 1 Site Map LIST OF TABLES Table 1 Beneficial Uses for Inland Surface Waters 7 Table 2 Surface Water Quality Objectives 8 Table 3 Beneficial Uses for Groundwater 9 Table 4 Groundwater Quality Objectives 10 Table 5 Historic Groundwater Quality 11 Table 6 Expected Increase in Selected Pollutants 13 Table 7 Water Quality of Selected Rivers 14 Table 8 Partial Listing of Domestic Water Quality Limitations 16 Water Quality Study Page i March 24, 1997 1330-02 1.0 PURPOSE OF THE WATER QUALITY REPORT The purpose of this water quality report is to assist the City of Carlsbad in preparing the environmental documentation meeting the National Environmental Protection Act (NEPA) and the Califomia Environmental Quality Act (CEQA) requirements for the construction of a replacement bridge on Rancho Santa Fe Road over San Marcos Creek. This report will determine the impacts on beneficial uses of surface water and groundwater due to changes in water quality associated with construction of the proposed project. An evaluation of the impacts of the bridge construction on water quality in San Marcos Creek will also be provided. Water Quality Study Page 1 March 24, 1997 1330-02 2.0 PROPOSED PROJECT Project Description The proposed project realigns and widens approximately 3,500 linear feet of Rancho Santa Fe Road (S-10) from two lanes to an ultimate 6-lane Prime Arterial Roadway from just south of Questhaven Road to just north of Melrose Drive in northem San Diego County (see Figure 1). The proposed widening and realignment project is a part of the City of Carlsbad's General Plan to upgrade Rancho Santa Fe Road to meet its designation as a Prime Arterial Roadway. A Prime Arterial Roadway has a 126-food right-of-way containing six traveled lanes, a bike lane, an 18-foot raised median, sidewalks, curb and gutter. The new bridge over San Marcos Creek is planned to accommodate the Prime Arterial Roadway. The bridge replacement project will involve construction of a new bridge in a location west of the existing bridge. The existing bridge will be demolished. Along with the new bridge, the project includes construction of roadway improvements in the south and north ends. The southerly roadway approach for the proposed bridge will extend approximately 1,800 feet which will include reconstructing the Questhaven and Rancho Santa Fe Roads intersection, and reconstructing approximately 600 to 800 feet of Questhaven Road east of the intersection. If the portion of Rancho Santa Fe Road located south of this project is delayed, then a detour will be used to join the Rancho Santa Fe Road Bridge approach with the existing alignment of Rancho Santa Fe Road. In this portion of the southem Prime Arterial Roadway, the project is to construct a 32-foot width of pavement on either side of the median curbs, inner two lanes in each direction plus 8-feet of the third lane, the median curbs, and the appropriate tum lanes. The northerly roadway approach for the new bridge(s) will be approximately 1,700 feet long and includes the reconstruction of the La Costa Meadows Drive/Rancho Santa Fe Road intersection, and the reconstruction of approximately 500 feet of La Costa Meadows Drive east of the intersection. The realigned Rancho Santa Fe Road will be constructed to the full width on the east side of the median, with sidewalks, curb and gutter and street lights from the bridge to north of Melrose Drive. The west side of the roadway will be constmcted with 32-feet of paving adjacent to the median curb. There are two altematives for the connection of Rancho Santa Fe Road with Melrose Drive: 1. The preferred altemative for the realigned Rancho Santa Fe Road is to match into existing Melrose Drive by curving to the west at the southerly end of the proposed Meadowland Subdivision (CT 85-19). This arrangement will necessitate closing the existing Corintia Street access to Melrose Drive and extending Xana Way southerly and easterly to meet Melrose Drive. Existing Rancho Santa Fe Road located north of the study area in San Marcos would be curved at its southerly terminus to "T" into the new Melrose/Rancho Santa Fe Road alignment. Water Quality Smdy Page 2 March 24, 1997 1330-02 2. The altemative alignment is for Rancho Santa Fe Road to match into existing Rancho Santa Fe Road similar to the existing arrangement. Melrose Drive would then swing east to intersect with Rancho Santa Fe Road in a location about 450 feet northerly of the present intersection. Corintia Street would extend east to intersect with the realigned Melrose Drive. Currently, Rancho Santa Fe Road is a two-lane conventional highway in northem San Diego County which connects the City of Encinitas in the south with the City of San Marcos to the north. The majority of the proposed project will lie within the City of Carlsbad with some project within the City of San Marcos. The proposed project alignment traverses rolling hill terrain and would generally be to the south and west of the existing Rancho Santa Fe Road alignment. The proposed project area has traditionally had low volumes of intra-regional and inter-regional traffic. However, there is anticipated to be future growth in the commercial and residential development along Rancho Santa Fe Road. This increase in traffic volume due to regional growth, coupled with projected local and regional increases in traffic volume associated with further development in this area, necessitate the widening of Rancho Santa Fe Road. The existing Rancho Santa Fe Road consists of two paved lanes with an asphalt berm on the west side and a combination of asphalt berm and concrete curb on the east side. A tmck by-pass route creates a three-plane paved road with asphalt berm on both sides in uphill areas of the stretch. San Marcos Creek is crossed by an existing bridge which is located between the Questhaven Road intersection and the Melrose Drive intersection. The Rancho Santa Fe Road has two northbound lanes and one southbound lane across the bridge. Water Quality Study Page 3 March 24, 1997 1330-02 3.0 HYDROLOGIC STUDY AREA The proposed project crosses San Marcos Creek just south of the intersection of Rancho Santa Fe Road and La Costa Meadows Drive in the City of Carlsbad. San Marcos Creek lies within Batiquitos Hydrologic Subarea (HSA) 4.51 of the San Marcos Hydrologic Area (HA) 4.50, of the Carlsbad Hydrologic Unit (HU) 4.0. The most prominent water feamre upstream of the project area is San Marcos Lake. Surface Water. San Marcos Creek drains an area approximately 46-square mile area north of the San Dieguito River Basin. The creek originates in the coastal range of mountains north and east of San Marcos. The drainage basin ranges in elevation from sea level to slightly more than 1,700 feet in the Merriam Mountain range northeast of San Marcos. The creek drains in Batiquitos Lagoon approximately 2.6 miles from the Pacific Ocean (MBA, 1992). The stream gradient ranges from an average of 10 feet per mile near the mouth to about 600 feet per mile near the headwaters. The creek has a small, not well-defined channel upstream from Lake San Marcos. Downstream of Lake San Marcos, the channel is more defined, steep and rocky to the La Costa development where it changes from well-defined to small and ill-defined to the Batiquitos Lagoon. In the immediate area of the project, the stream is broad and well- defined. Groundwater. San Marcos Creek is a perennial stream. The depth to groundwater in the alluvium area is between 2 to 5 feet below ground surface. The alluvium thickness generally ranges from 4 to 10 feet below ground surface. Geology. The area surrounding the Rancho Santa Fe bridge site has one geologic formation and one surficial soil type. The geologic formation consists of the Cretaceous-aged Bonsall Tonalite. The surficial soil deposit consists of alluvium. In the Rancho Santa Fe Road Realignment area, additional geologic formations of the Jurassic-aged Santiago Peak Volcanics and the Eocene-aged Delmar Formation are identified. Additional surficial soil deposits in the project area include terrace deposits, landslide debris and surficial landslide debris, slopewash, topsoil, and fill material. The following gives a brief description of the geology of the site. More comprehensive geologic investigations may be found in reports from Geocon (1990). Santiago Peak Volcanics. The Santiago Peak Volcanics comprises much of the underlying rock except for the extreme northerly one-fourth of the project site. The rocks were deposited as an altemating secession of volcanic flows, tuffs and breccias. The majority of the Santiago Peak Volcanics is highly fractured and altered. Bonsall Tonalite. Bonsall Tonalite comprises the bedrock material underlying the area of the bridge. The weathered granitic rock is characterized by a dense to very dense, light brown, weathered Bonsall Tonalite that excavates to a fine- to coarse-grained sand with gravel and cobble size fragments. In the San Marcos Creek channel, the granitic rock is 5 to 10 feet from the existing ground surface. Water Quality Study Page 4 March 24. 1997 1330-02 Delmar Formation. The Eocene-aged Delmar Formation consists of stiff to very hard, light brown to olive silty to sandy claystones and sandstones. This formation occurs only in the lower drainage area to Encinitas Creek. Terrace deposits. Terrace deposits are stream-deposited dense, dark reddish-brown sands and cobble-to-boulder conglomerates overlying the Santiago Peak Volcanics and the Delmar Formation. Alluvium. Alluvial soils are encountered at the surface within the majority of the low- lying portions of the site including the northem channel embankment and within the San Marcos Creek channel. Alluvial soils are characterized by loose to moderately dense, moist to saturated, dark brown silty and clayey sands with some gravel and cobble. The thickness of the alluvium generally ranges between 4 to 10 feet. Landslide Debris and Surficial Landslide Debris. Two deep-seated landslides and two areas of surficial landslides were identified in the project area. Slopewash. Slopewash and coUuvial soils occur along the canyon side-slopes at the base of namral slopes and along the head of landslides. These deposits are often indistinguishable form alluvium and thick topsoil deposits. Topsoil. Topsoils are characterized by dark brown to reddish-brown gravelly silty sands to sandy clays. Fill Material. Areas of fill material have been identified in the project area. The largest volume of documented fill includes the materials constituting La Costa Dam. Water Quality Study Page 5 March 24, 1997 1330-02 4.0 EXISTING WATER QUALITY The Califomia Regional Water Quality Control Board (RWQCB) sets forth water quality objectives for the various water bodies in this region. These objectives and beneficial uses designations may be found in the Water Quality Control Plan for the San Diego Region (9) authored by the RWQCB (1994). Surface Water. The beneficial uses and water quality objectives for surface water in the Batiquitos HSA are listed in Tables 1 and 2. Water quality data for the study area were not available from published sources. Groundwater. The groundwater beneficial uses for HSA 4.51 is listed in Table 3 and the groundwater quality objectives are listed in Table 4. Historic data on water quality from published sources are listed in Table 5. Water Quality Study Page 6 March 24, 1997 1330-02 TABLE 1 BENEFICIAL USES FOR INLAND SURFACE WATERS MUN Municipal and Domestic Supply + AGR Agricultural Supply • IND Industrial Services Supply PROC Industrial Process Supply GWR Groundwater Recharge FRSH Freshwater Replenishment POW Hydropower Generation REC-1 Water Contact Recreation • REC-2 Non-Contact Water Recreation • BIOL Preservation of Biological Habitats of Special Significance WARM Warm Fresh-Water Habitat • COLD Cold Fresh-Water Habitat WILD Wildlife Habitat • RARE Preservation of Rare and Endangered Species SPWM Fish Spawning + Exempt from MUN • Existing Beneficial Use Source: RWQCB (1994). Water Quality Study March 24, 1997 Page 7 1330-02 TABLE 2 SURFACE WATER QUALITY OBJECTIVES HA 4.50 Total Dissolved Solids 500 mg/1 Chloride 250 mg/1 Sulfate 250 mg/1 Sodium (percent) 60 Nitrogen and Phosphoms A Iron 0.3 mg/1 Manganese 0.05 mg/1 Methylene Blue Active Substances (MBAS) 0.5 mg/1 Boron 0.75 mg/1 Odor None Turbidity 20 NTU Color 20 units Fluoride 1.0 mg/1 Notes: Concentrations of nitrogen and phosphorus, by themselves or in combination with other nutrients, shall be ^ maintained at levels below those which stimulate algae and emergent plant growth. Threshold total phosphorus (?) concentrations shall not exceed 0.05 mg/1 in any stream at the point where it enters any standing body of water, nor 0.025 mg/1 in any standing body of water. A desired goal in order to prevent plant nuisances in streams and other flowing waters appears to be 0.1 mg/1 total P. These values are not be exceeded more than 10 percent of the time unless studies for the specific water body in question show Uiat water quality objective changes are permissible and changes are approved by the Regional Board. Analogous threshold values have not been set for nitrogen compounds; however, natural ratios of nitrogen to phosphorus are to be determined by surveillance and upheld. If data are lacking, a ratio of N:P - 10:1 shall be used. The water quality objectives do not apply westerly of the easterly boundary of Interstate Highway 5. The water quality objectives do not apply to hydrologic subareas 4.51 and 4.52 between Highway 78 and El Camino Real and to all lands which drain to Moonlight and Encinitas Creek. The water quality objectives do not apply to the portion of Subarea 4.51 bounded on the south the north shore of Batiquitos Lagoon, on the west by the easterly boundary of the Interstate 5 right-of-way and on the east by the easterly boundary of El Camino Real. The objectives for the remainder of the Hydrologic Area are as shown. Reference: RWQCB (1994). Water Quality Smdy March 24, 1997 Page 8 1330-02 TABLES BENEFICIAL USES FOR GROUNDWATER HSA 4.51 MUN Municipal and Domestic Supply • AGR Agricultural Supply • IND Industrial Services Supply • PROC Industrial Process Supply GWR Groundwater Recharge FRSH Freshwater Replenishment Reference: RWQCB (1994). Water Quality Smdy March 24, 1997 Page 9 1330-02 TABLES BENEFICIAL USES FOR GROUNDWATER HSA 4.51 MUN Municipal and Domestic Supply • AGR Agricultural Supply • IND Industrial Services Supply • PROC Industrial Process Supply GWR Groundwater Recharge FRSH Freshwater Replenishment Reference: RWQCB (1994). Water Quality Smdy March 24, 1997 Page 9 1330-02 Water Quality Smdy March 24, 1997 Page 10 1330-02 TABLE 6 HISTORIC WATER QUALITY DATA Well No. 12S/ Date Temp. (°F) Ca Mg Na K HOC3 SO4 Cl NO3 Fl B TDS Hard- ness pH 3W-16L 8/53 — 508 217 970 3 117 486 2548 19.2 0.3 .01 4839 2162 7.2 4W-26H 10/63 76 46 30 215 2 221 92 297 0 0.6 0.33 818 239 8.2 4W-26N 10/61 ~ 72 3 387 1 46 447 365 0 0.9 1.3 1310 192 7.2 4W-35L 8/54 70 116 54 280 2 400 193 390 51 0.1 0.45 1283 512 7.8 4W-36C 7/61 72 54 66 281 1 354 190 369 27 0.5 0.26 1175 406 8.0 4W-36E 7/61 74 194 108 451 11 360 399 869 14 0.7 0.23 2249 929 7.8 All units in mg/1 unless otherwise noted. Reference: California Department of Water Resources (1967). Water Quality Smdy March 24, 1997 Page 11 1330-02 5.0 ENVIRONMENTAL EVALUATION The proposed project widening and realignment of Rancho Santa Fe Road and bridge is expected to have potential water quality impacts during the constmction and operational phase. Construction Phase. The constmction of the realignment of Rancho Santa Fe Road, including grading and cut and fills, would entail the movement of approximately 265,000 cubic yards of earth and the creation of manufacmred cut and fills. The maximum height of cut slope is estimated to be about 50 feet and the maximum amount fill slope is estimated to be 20 feet. This movement of sediment and grading of the alignment will create potential for sediment increases to San Marcos Creek. Best Management Practices (BMPs) to reduce sediment load to the creek should be followed. Such practices include dust control such as covering bed loads on transport tmcks, installation of straw bale berms along the creek front to filter discharges entering the creek, and other measures. Limiting grading to the smallest practical area to reduce the amount of exposed surface area will also minimize erosion due to the elements. The demolition of the existing bridge will probably include the removal of the abutments and piers. The constmction of the new bridge will also include the installation of new piers. The removal and installation of the piers will create dismrbance of the river channel. The sediment loading to the river could be substantial, depending on the season when constmction occurs. The State Water Quality Control Board (SWQCB) requires constmction activity dismrbing more than 5 acres apply for a Notice of Intent (NOI) for coverage under the General Constmction Activity Storm Water Permit to treat storm water discharging to San Marcos Creek. The permit requires the visual checking of pollutants discharging to the creek. The permit also requires the preparation of a Storm Water Pollution Prevention Plan (SWPPP) that would detail actions taken to prevent contaminated storm water from entering the receiving water and a monitoring plan for pollutants. A condition of closure of the General Constmction Activity Storm Water Permit is that best management practices (BMPs) be in place for post-constmction treatment of storm water discharges before the permit will be released. It would be the City of Carlsbad's responsibility to ensure the BMPs are operational and effective in reducing storm water pollutants during the post-constmction phase. Operational Phase. The proposed project would have approximately 8 acres of paved surface area which is almost 3 times the amount of the current paved area. Increases in surface mnoff and pollutant loads may be expected. Estimating Highway Runoff Quality (Racin, 1982) characterizes pollutant loads from roadways. Some conclusions are: 1. Roadways are potential sources of non-point source pollution as paved surfaces accumulate pollutants and during rainfall events can discharge these pollutants to water bodies. Water Quality Smdy Page 12 March 24, 1997 1330-02 2. Dry days before the storm are used as means of estimating pollutant accumulation. 3. Chemical oxygen demand (COD), dissolved solids (DS), lead, total Kjeldahl nitrogen (TKN), and zinc are statistically correlated with vehicles during the storm. COD, suspended solids (SS), and zinc were statistically correlated with total residue. 4. The number of dry days between storm events and the corresponding cumulative traffic volume before the storm were found to be not statistically significant. It appears that traffic-generated mrbulence tends to "sweep" the traveled lanes and shoulders, thus moving the pollutants off the roadway. 5. Boron, cadmium, nitrate nitrogen, ammonia nitrogen, total phosphoms, dissolved orthophosphate, and oil and grease were not correlated with any independent variable. Independent variables chosen for analysis were number of dry days before storm events, number of vehicles, maximum rainfall, and mnoff volume. 6. Sulfate, iron, chromium, copper, manganese, nickel, bicarbonate ion, carbonate ion, calcium, magnesium, chloride, mercury, molybdenum, potassium, silica, and sodium exhibited a "first flush" pattem with relatively insignificant concentrations. 7. Urban highways in Califomia do not produce large masses of pollutants which would discharge to receiving waters during storm events. This conclusion was based on the assumption that the highway segment is between 2 and 3 acres and the average daily traffic (ADT) would be greater than 30,000. This report developed empirical regression equations for calculating the constiment loads of lead, zinc, DS, COD, TKN, total residue, and SS from paved travelled way and shoulder areas. These equations were used to estimate pollutant loads for this project. (See Appendix A for calculations). The results are shown in Table 6. Loads were calculated for each 855 linear feet of roadway based upon the assumption of a 2 acre area of analyses. Surface Water. Although there is no water quality data for San Marcos Creek, water quality data for San Dieguito River (1946-1981), downstream of Hodges Dam, and for Escondido Creek (1974-1981), downstream of Harmony Grove is shown in Table 7. Since these two rivers also drain urbanized areas, the water quality of San Marcos Creek is expected to be similar. Only a sampling program will determine the actaal water quality of San Marcos Creek. Under the assumption that water quality of the San Dieguito River and Escondido Creek are indicative of the water quality of San Marcos Creek, the data indicate the surface water quality objectives of dissolved solids, sulfate, and boron are exceeded. There is no data on the other constiments listed in the surface water quality objectives for comparison with the objective. Groundwater. Historic groundwater quality is listed in Table 5. If well 12S/3W-16L can be considered an anomaly and removed from further consideration since it has much higher concentrations of all the constiments listed, then the historic groundwater quality can be considered to be fairly good. The only water quality objectives exceeded are chloride in well 12S/4W-36E and nitrate in well 12S/4W-35L. Water Quality Smdy Page 13 March 24, 1997 1330-02 TABLE 6 Constiment Existing Concentration (mg/1) Possible Future Concentration (mg/1) Percent Increase Lead (Pb) 0.34 0.5 46 Zinc (Zn) 0.14 0.19 24 Dissolved Solids 37.6 49.6 32 Chemical Oxygen Demand (COD) 45.4 64.3 42 Total Kjeldahl Nitrogen (TKN) 0.97 1.27 31 Total Solids 163 247 52 Suspended Solids 103 158 53 TABLE 7 WATER QUALITY OF SELECTED RIVERS Constituent San Dieguito River' (mg/1) Escondido Creek^ (mg/1) Dissolved Solids 1120 1240 Sodium 130 220 Calcium 96 84 Magnesium 38 61 Chloride 130 330 Sulfate 290 270 Alkalinity 167 Boron 170 Reference 1 Izbicki (1983). 2 Woolfenden (1989). Water Quality Smdy March 24, 1997 Page 14 1330-02 Waters identified as having as "municipal and domestic supply" should meet the water quality limitations in Table 8 as well as the groundwater quality objectives (Table 4). Table 8 represents a partial listing of the water quality limitations for beneficial use. When the expected pollutant loads for the storm water mnoff are compared to the domestic water quality limitations listed in Table 8, the expected lead load exceeds the standards. The zinc and dissolved solids, however, are well below the limitations. These results, combined with the finding of the Racin (1982) smdy, indicate only lead discharges would be of concem. Lead is a component of some gasoline, therefore, would be impossible to eliminate from surface mnoff. Water Quality Smdy Page 15 March 24, 1997 1330-02 TABLE 8 PARTIAL LISTING OF DOMESTIC WATER QUALITY LIMITATIONS Constituent Primary (mg/1) Secondary (mg/1) Constituent Primary (mg/1) Recommended Upper Limit Inorganic Chemical Arsenic 0.05 Barium 1.0 Cadmium 0.01 Chromium 0.05 Lead 0.05 Mercury 0.002 Selenium 0.01 Silver 0.05 Fluoride 1.4-2.4 Nitrate 45.0 General Mineral Chloride 250 500 Copper 1.0 MBAS 0.5 Iron 0.3 Manganese 0.05 Sulfate 250 500 Specific Conductance 900 1600 Total Dissolved Solids 500 1000 Zinc 5.0 General Physical Color 15 units Odor-Threshold 3 units Turbidity 5 units Source: RWQCB, 1994. Water Quality Study March 24, 1997 Page 16 1330-02 6.0 DISCUSSION The results of the Racin (1982) smdy showed that the amount and type of pollutants are minimal for a roadway of this size. Of the parameters identified in the smdy as being of concem, only the expected pollutant load of lead may pose a problem. The expected pollutant lead load exceeds the domestic water quality limitations; there is no groundwater quality objective. It may be impossible to mitigate lead loads. 6.1 SURFACE WATER The storm water mnoff to San Marcos Creek would be regulated by the General Constmction Activity Permit for Storm Water Runoff. A requirement of this permit is that BMP's be implemented during and post-constmction to reduce storm water mnoff pollutants from entering the river. The City of Carlsbad would be responsible for ensuring BMP's are operational and effective in reducing pollutants. A review of similar water quality data show the expected water quality in San Marcos Creek to be fairly good. A review of the expected pollutant loads to San Marcos Creek from storm water mnoff from the new roadway is expected to be small. Constmction Phase. The demolition of the existing bridge and the constmction of the proposed Rancho Santa Fe Road bridge will create a large disturbance in the river channel. The dismrbance will increase the sediment loading downstream of bridge constmction. One method to minimize impacts to water quality would be to limit dismrbances in the river channel to the dry season (March to October). Operational Phase. The expected water quality in San Marcos River is fairly good. Additional loads due to storm water mnoff from 855 feet of roadway will add a small amount of loading to San Marcos Creek. These concentrations would be below the surface water quality objectives and therefore will not further degrade the surface water quality. The 24-hour storm event with a 25-year remm interval is expected to produce a mnoff volume of 0.37 cfs for each 855 feet of roadway (see Appendix A). The expected mnoff from the length of the new roadway in this project would produce a flow of approximately 1.53 cfs which in small comparison with the 25- year flood flow of 4,500 cfs. The storm water mnoff volume is 0.034 percent of the 25-year flood flow. 6.2 GROUNDWATER The only constiment present in groundwater identified by the Racin (1982) smdy that may be of concem is lead. Lead is emitted from vehicle exhaust in the aerosol/particulate form and settles onto the highway. Calculations based on the Racin smdy show 0.5 mg/1 to be the expected concentration during storm water events. Since the groundwater has a beneficial use of "municipal and domestic supply" the limitation for this beneficial use is 0.05 mg/1. Water Quality Study Page 17 March 24, 1997 1330-02 7.0 CONCLUSIONS AND RECOMMENDATIONS The surface and groundwater objectives as identified in the Basin Plan are being exceeded by some constiments at existing conditions. The project is expected to add some pollutants to the receiving water bodies, but in amounts well below the water quality objectives of both the surface and groundwater. Mitigation measures are only valid for surface water. Groundwater quality cannot be mitigated except to control the quality of the surface water that will seep into the basin. Since this amount is expected to be small, no mitigation measures are required. Construction Phase. During the constmction phase, BMPs should be applied to control storm water mnoff and to provide dust control. Some possible mitigation measures include: ~ gravel berms, filter fabric fences, lines of straw bales, etc. to prevent erosion, — surfacing of roadways should occur as soon as possible, — periodic watering of areas to keep dust down, and — prompt revegetation of surrounding areas to prevent erosion. The storm water pollution prevention plan (SWPPP) as identified in the constmction activity permit from the RWQCB should be implemented and followed. To minimize water quality degradation by sedimentation of the river channel during constmction, constmction of the new piers and demolition of the existing piers should be limited to the dry season (March to October). Operational Phase. The roadway should be provided with devices for storm water treatment. These devices should capmre and treat the storm water prior to discharge to the river. BMPs should be applied to reduce pollutant loads to the river. Analysis has shown pollutant loads for this project, however, are expected to be minimal. Tmcking accidents may also occur where large spills of transported material may discharge to the river. Any type of treatment facilities incorporated into the design for storm water treatment of highway mnoff may have the added benefit of collecting these spill releases before entering the river. Water Quality Smdy Page 18 March 24, 1997 1330-02 8.0 REFERENCES California Department of Water Resources (1967). Ground Water Occurrence and Quality: San Diego Region. Volume I, Text. Bulletin No. 106-2. Califomia Regional Water Quality Control Board (1994). Water Quality Control Plan for the San Diego Basin (9). Michael Brandman Associates (1992). Draft Environmental Impact Report - San Marcos Flood Control Channel - San Marcos Creek/Las Posas Reach. SCH #92011033. Cotton/Beland/Associates, Inc. (1989). Draft Environmental Impact Report for the Rancho Santa Fe Road Realignment and Mass Grading. SCH #90010850. Geocon, Inc. (1990). Bridge Foundation Investigation for Rancho Santa Fe Road Realignment, Rancho Santa Fe Bridge Crossing at San Marcos Creek, Carlsbad, California. Geocon, Inc. (1990). Supplemental Soil and Geologic Investigation for Rancho Santa Fe Road Realignment, Carlsbad, Califomia. January. Goodridge, J.D., et al. (1976). Rainfall Analysis for Drainage Design, Vol. II., Long Duration Precipitation Frequency Data. Califomia Department of Water Resources, Bulletin No. 195. Izbicki, J., (1983). Evaluation ofthe San Dieguito, San Elijo, and San Pasqual Hydrologic Subareas for Reclaimed Water Use, San Diego County, Califomia. Water-Resources Investigations Report 83-4044. Racin, James A., et al. (1982). Estimating Highway Runoff Quality. FHWA/CA/Tl-82-11. Woolfenden, L.R., (1989). Geohydrology ofthe Escondido Hydrologic Subarea, San Diego County, Califomia. Water-Resources Investigations Report 88-4223. Water Quality Smdy Page 19 March 25, 1997 1330-02 APPENDIX CALCULATIONS c 10-. p. oc^to CATPT) TlCiJ » ISO + p. 6e34J- C^PT) ^ - ^.>s-^ o.ootf &4-6Tft.-) (D AroT >3.o, 0=0 <?sr o-* 5 UirOCi Cfi l^' e-itti) 4,©' S.O ueotTH MUST (J^X'^SSfco) ' ^v^. v«j6 tj. e3.r,>-v.t<r. •DUDEK & PROJECT: ^otro (^gto-i^KlKfeOT •ASSOCIATES, INC. BYc^ DATEV-^^M 10x10 JOB NO. \'^3o-o2. CHKD BY DATE SHEET OF ' -^VT, ^ ^7 ^ = o.V^XZ C^c/$,<*"^ con* 7{/!P(?* 0,u*(S^ tfl* fIjCCi? 1/i DUDEK & ASSOCIATES, INC. PROJECT: (2-S.F ^eAvx<:.Kl ufehTT 10x10 JOB NO. PSo-o^ BY ^ DATE Y^n/*!^ CHKD BY. DATE SHEET ^ OF ^ = ITS OS .3 5^ r *7 2: ISg) I DUDEK & ASSOCIATES, INC. PROJECT: P^f 9of^ ^^1^ BY Ju DATE yM/^f CHKD BY DATE. 10x10 JOB NO.^^^g'g^ SHEET 3 OF 4- ^ 5- •DUDEK & •A 'ASSOCIATES, INC. PROJECT: t^brO l^^fervi^<^Hg^ BY DATE yj^^^-^ CHKD BY DATE 10x10 JOB NO. 13^0-02. SHEET ^ OF 4" I i I I I I I I I I i 1 1 i i I 1C3 • fRCC I'll »T10X OC'Tx-OumTIOx-rKCOUCxC' T»»LC ELtV SEC T.P »MC LOT »•» L'TITUOt LONOITUOE COUNTt cool 3UC Zi lOS ojt D S 3J.?»5 ll».»3l »C KillMUM »RCCI'ntT10K ^OK IMClCiTtO DURATION D-B4TS B-KOURS •RtTURh PE«IOB X Tt»RS 10 2 .2.03 •5 3.10 u 3.15 ZO 25 • .«1 • 0 4.29 So i.it 100 ».22 200 t.Vl 1000 t.SO 10000 lO.T* lO.SO CLOCK MB, COR. C»LCUL*TtD SKEW REOION»l SKEtl SKC» yuD KURTOSIS N RECORD TEAR RECORO HiXlHuM NORHtLIZEO »*X C*LC. cotr. V*» RE«N. COEr. VAR USED COEr. VAR MEAh/A RPIO/A RP2S/A RPSO/A RPJCO/A RPlOOl/* RPleOOt/A PdP/A 2.326 1:1*2? l.ooo > l.kOO 5.5*3 IT 1'2T 5.Oto 2.OS0 .530 • 1*10 .2336 .2*17 .33*7 .3771 .5152 .050* l.lOOO .20 2.»7 «.1» 5.15 i.l2 t.*2 7.0* 7.36 6.26 l.iO 11.27 1*.10 26,62 3.051 V.iU 1.500 1.500 5.2»7 67 1027 i.o'o 3.160 .521 .515 .515 .1*50 .3110 .3003 .**62 .5022 .603* • •605 1.6137 30 2.05 *.62 3.60 6.03 7.30 0.05 • .*0 O.So 10.50 13.06 16,57 30.36 3.606 i-.m 1 .600 1.600 7.1*5 67 1«27 0.020 3.*0T .530 .5?B ,52a .2065 .351* .**23 .5005 .5750 ,7020 1.00*3 I.OAIO 13 00 ,15 ,36 .7* ,5* ,02 35 23 ,53 ,77 .16 ,06 37 10.0> 11.23 13.07 17,50 32.2S 3.616 i:8?» 1 ,600 1.600 7,623 67 1027 10.730 3.»71 .567 .52« .526 .2102 •.llli .5*00 .6113 .6*0* J.0662 1.0553 10.55 11.72 1*.30 H,l» 3*.10 «0 3.56 5.-55 6.60 6.17 6.57 O,*0 0.79 10.00 12.17 1«.66 16,61 35,05 • O 3.03 6.06 7.*8 6,63 0.25 10.12 10.53 11.76 13,01 15.70 10,66 36.66 100 *.22 6.** T.OO 0.2T O.T; lo.so 10.0' 12.2» 13.tT 16,2» 20.07 *0,6i 3.035 '*.060 *,*06 wm \:m 1.500 1 .^00 1.300 1>500 1 .*00 1.300 7.*** 6,030 10.'03 67 67 67 1022 1022 1022 12.160 12.160 17.160 3.732 3.520 *.613 .562 .565 .601 .526 .522 .521 .526 .522 .521 .2325 .3*56 .*O50 .5611 ,6300 .'727 1.lool 2.0672 .2»62 .*179 .5105 .5036 .6665 .Ooo* I.J28* 2.1735 .2673 .•537 .5606 .6366 .71** .0573 1.1916 2.3560 *.666 I .OOn 2.3*9 1.200 1,200 11.25] 67 1022 16.36 0 t.6a6 .506 .512 .512 .26*1 .*70l ,5676 .6662 .7*23 ,96*» 1.2170 2.6662 ISO 1.61 7,35 O.Ol 10.57 11.06 12.06 12.53 13.97 15.37 16,53 22.01 *6.*3 5.3*0 1 .200 1.200 9,612 67 1022 19.666 *,**6 .612 .513 .513 .3237 • 5*6* ,670* ,7500 .6*66 1.123* 1.3667 2.61*' 200 5.32 6.03 0.77 11.30 11.OO 12.1* 13.*2 1*.66 16,32 10.53 23,06 • 0.77 S.6*6 300 '6,21 0.20 11,10 12.6^ 13.36 15.00 16.56 16.ol 21.*S 26,o6 55,*2 6.7*7 V.iii 600 6.36 12.^7 15.07 17.*7 16.21 19,73 20.*• 22.56 2*. 66 20.32 35,66 76.05 3650 15,26 21.61 25.60 29.•O 30.67 31,25 3*.23 37.67 41.03 • 6.56 5f.93 119.*2 9.001 16,«9* 1,100 1.000 1 .000 1.100 1.100 1.000 i.OOD 1.100 0.003 7.720 5.526 • .132 67 67 67 70 1022 1022 1922 1022 21.660 21.660 25.660 36.230 *.*56 *.0O2 3,663 3.367 .615 .5*7 .*9e .369 ,501 .*61 .•91 .•16 .501 .*61 ,•91 .•16 .35** .5925 .7212 .6133 .902^ 1.1*^2 M«525 3.0177 .•090 .6727 .6109 ,9092 1.0037 1.3005 1.5S10 3.3602 .5512 .0130 1.1060 1.2301 1.3691 1.777* 2-1632 *.6105 1.0000 1.5576 1,6593 2.0753 2.2660 2.9**2 3.5729 7.2*00 STATION NO. (SN ORDER SOB ZO* 26*0 1 ? RESERVOIR STATION NtHE PRECIPITATION DEPTM-DURATION-FREOUENCY TABLE ELEV SEC T»P RNO LOT B"M 373 752 16 IIS 03K S LATITUDE LONOIToDE COUNTY CODE 33.217 117.217 00 NAXINUM PHECI'-JTATION FOR INDICATED DURATION D-DAYS H-MOURS IN TEARS ID 2 1.66 5 2.67 10 3.57 20 *.2* 25 *.*6 *0 *.9o SO 5.11 leo 5.76 .200 6.*0 Itoo 7.67 10000 9,9* PMP 16.12 20 2.27 3.51 ».3' 5.20 5.*6 6.00 6,25 7,0* 7.61 9.56 12.06 22.62 MEAN • CLOCK NR. COR. CALCULATED SKEW RESION'AL »^E» SKEK USED KuRTOSIS N RECORD TEAR RECORD MAXIMUM NORMALIZED MAX C*LC. COEF. VAR REBN. COEF, V*R USED COEF, VAR MEAN/A RPIO/* RP2?/* RP»6/« RPlOO/A RPlOOO/* RPie«oo/A •PMP/A •2.15A l.Uo .752 1.600 1.600 3.062 32 lO^l 3.620 2.020 .363 .»9* ,*9* .1662 • l766 .3*79 .3091 .**97 .614* .7762 1.41*5 2.592 1.070 .30* 1.500 1.500 2.665 32 19*1 4.360 1.632 .376 .515 .515 .2024 .3*13 .*260 .*663 .5*05 .7*76 .9416 1.7657 30 2.4* 3.62 ..79 5.73 6.03 6.6S 6.0* 7.6* 6.7* 10.79 13.66 25.09 2.613 1.0*0 -0.632 1.600 1,600 2.265 32 19*1 4,360 1.505 .370 .526 .526 .2196 .3737 ,47o* .5*19 .6125 .6*2* 1.0662 1.9569 *D 2.54 3.96 •.»' 5.07 6.26 &.93 7.24 6.16 9.11 11.25 14.27 26.17 2.934 1.020 .236 1.600 1.600 2,766 32 1936 5,350 2,156 .362 .526 .526 .2291 .3696 .4906 .5652 .6366 .6766 1.1141 2.0431 50 2.67 4.17 5.20 6.1O 6.51 7.16 7.47 6.41 0.34 1X.47 14.46 27.17 3.CS7 l.OlO '.360 1.500 I.SOO 2.930 32 1030 5.700 2.335 .370 .526 .526 ,2366 .4060 .5060 .5630 .6567 ,6955 1.1269 2.121* 6D 2.63 4.36 S.44 6.44 6.76 7.42 7.72 6.67 9.60 11.72 14.61 26.27 3.202 l.OlO .416 1.400 1.400 2.760 32 1*36 5.020 2.2*6 .376 .522 .522 .2500 .4244 ,5276 .6031 .6760 .9140 1.1461 2.2074 BD 100 ISO 2.95 3.33 3.76 4.55 5.00 5.66 5.62 6.25 6.94 6.63 7.33 6.14 6.05 7.67 6.51 7.61 6.36 9.29 7.01 6.69 9.65 • .as 9.66 10.75 9.TT 10.65 11.63 11.66 12.6* 14.26 14.77 15.B7 17.63 29.20 32.16 • 35.74 3.312 1 .060 .356 1.300 1.300 3.70S 1.060 .376 1.200 1.200 4.111 1.000 .360 1.200 1.200 20D 4.10 6,19 7,53 B,7i 0.17 9,36 10.34 11.46 12.96 15.66 16.47 36.3* 4.5o7 1.000 .196 1.160 1.160 300 4,94 7.32 t,B3 10.21 10.64 11.92 11.93 13.17 14.37 17.06 20.74 44. g6 5.366 1.000 .261 1.000 1.000 60D 6.66 10.24 12.37 14.34 14.99 16.20 16.7* IB.94 20.29 24.07 19.2* 62.43 7.663 1.000 .679 i.ooo i.ooo 3690 li.*5 16.76 19.OS 22. *0 23. B2 24.26 26.56 29.25 31.(6 37.71 49.76 *2.73 12.*** 1,000 1.112 1,100 1.100 2.602 2.436 2.4** 32 32 32 1938 l96t 193* 9.920 6.400 7.430 2.037 2.102 l.(*l 7.430 2.037 .375 .521 .3*7 .306 .375 .521 .912 .513 .921 .512 .913 2.314 2 .760 3.206 4,921 32 32 32 32 193* 1941 1*41 7.900 9 .970 14.930 26,470 1.737 1 .066 2.304 2.973 .3*2 .3*5 .434 .414 .901 .4(1 .4*1 .416 .901 .4*1 .4*1 .416 .2566 .43*0 ,5426 .617* • 6*12 .6262 1.1*32 2.27*9 .26*3 .4676 .9064 .6762 .7957 1.0024 1.23*0 2.9106 .320* .5416 ,6646 .7933 .(3*4 1.1136 1.3767 2,7*09 .3910 .5663 .7160 .6079 .6*60 1.1757 i.4422 2.»»62 .416* .66*0 .6306 .0312 1.0260 1.3320 1.61*3 3.4616 .9626 .*661 1.1676 1.30*0 1.4473 1.67*0 2.2*6* 4.•730 1.0000 1.997* l.«5*3 2.0753 2.2*40 2.9442 3.5729 7^2400 PEARSON TYPE 111 DISTRIBUTION USED . PRSSABLE KAXIMLPH PRECIPITATION ESTIMATE BASED ON IS STANDARD DEVIATIONS •MERE N IS SMALL RESULTS ARE HOT DEPENDABLE 369 — LEGEND — . PRECIPITATION STATION LOCATION STATION NUMEER (DAILY) »c»i.l Of M.-tJ June 1976 FIGURES