HomeMy WebLinkAbout3190; Rancho Sante Fe Road Bridge Replacement; Rancho Sante Fe Road Bridge Replacement; 1997-03-24WATER QUALITY STUDY
RANCHO SANTA FE ROAD BRIDGE REPLACEMENT PROJECT
Submitted To:
CITY OF CARLSBAD
2075 Las Palmas Drive
Carlsbad, CA 92009-1576
ATTN: Doug Helming
Prepared By:
DUDEK & ASSOCLVTES, INC.
605 Third Street
Encinitas, CA 92024
ATTN: Gail Masutani
March 24, 1997
TABLE OF CONTENTS
Page
mm No.
MM
LIST OF FIGURES
MH
LIST OF TABLES
1.0 PURPOSE OF REPORT 1 1.0
2.0 PROPOSED PROJECT 2
Mi 3.0 HYDROLOGIC STUDY AREA 4
4.0 EXISTING WATER QUALITY 6 EXISTING WATER QUALITY
-5.0 ENVIRONMENTAL EVALUATION 12
6.0 DISCUSSION 17
MM
6.0
6.1 Surface Water 17
17
7.0 CONCLUSIONS AND RECOMMENDATIONS 18
8.0 REFERENCES 19 8.0
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 Selecled 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 VS^ATER 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 reconstmcting the Questhaven and Rancho Santa
Fe Roads intersection, and reconstmcting approximately 600 to 800 feet of Questhaven Road
east of the mtersection. 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 aUgnment of Rancho Santa Fe Road. In this portion of the southem Prime Arterial
Roadway, the project is to constmct 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 reconstmction of the La Costa Meadows Drive/Rancho Santa Fe Road intersection,
and the reconstmction of approximately 500 feet of La Costa Meadows Drive east of the
intersection. The realigned Rancho Santa Fe Road will be consttucted 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 mto
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 Meirose/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 northera 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 fumre 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 Smdy 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 ofthe 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 drauiage 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-defmed to small and ill-defined
to the Batiquitos Lagoon. In the immediate area of the project, the stream is broad and well-
defmed.
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 ofthe
Santiago Peak Volcanics is highly fracmred 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 Smdy 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 northera channel embankment and within the San Marcos
Creek channel. Alluvial soils are characterized by loose to moderately dense, moist to samrated,
dark brown silty and clayey sands with some gravel and cobble. The thickness of the alluvium
generally ranges between 4 to 10 feet.
LandsUde Debris and Surficial Landslide Debris. Two deep-seated landslides and two
areas of surficial landslides were identified in the project area.
Slopewash. Slopewash and colluvial soils occur along the canyon side-slopes at the base
of namral slopes and along the head of landsUdes. 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.
FiU Material. Areas of fill material have been identified in the project area. The largest
volume of documented fill includes the materials constimting La Costa Dam.
Water Quality Smdy 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 Usted in Tables 1 and 2. Water quality data for the smdy 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 pubUshed sources are listed in Table 5.
Water Quality Smdy Page 6
March 24, 1997 1330-02
TABLE 1
BENEFICIAL USES FOR INLAND SURFACE
WATERS
MUN Municipal and Domestic Supply -1-
AGR Agriculmral 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
e Existing Beneficial Use
Source: RWQCB (1994).
Water Quality Smdy
March 24, 1997
Page 7
1330-02
mm TABLE 2
SURFACE WATER QUALITY OBJECTIVES
•mm HA 4.50
— Total Dissolved Solids 500 mg/l
«•
Chloride 250 mg/I
«•«
Sulfate 250 mg/l
Sodium (percent) 60
Nitrogen and Phosphoms A
Iron 0.3 mg/l
Manganese 0.05 mg/l
Methylene Blue Active Substances (MBAS) 0.5 mg/l
Boron 0.75 mg/l
Odor None
IM Turbidity 20 NTU
mm Color 20 units
mm Fluoride 1.0 mg/l
IMM
•n—
Notes:
^ Concentrations of nitrogen and phosphonis, 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 (P)
concentrations shall not exceed O.OS mg/l in any stream at the point where it enters any standing body of water, nor
0.025 mg/l in any standing body of water. A desired goal in order to prevent plant nuisances in streams and other
flowing waters appears to bc 0.1 mg/l tolal P. These values are not bc exceeded more than 10 percent of the time
unless studies for the specific water body in question show th^ 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 arc lacking, a ratio of N:P - 10:1 shall be used.
tM
The water quality objectives do not apply westerly of thc easterly boundary of Interstate Highway 5. Thc water
quality objectives do not ^ply to hydrologic subareas 4.S1 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 EI Camino Real. The objectives for the
remainder of thc Hydrologic Area are as shown.
MH
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 Agriculmral Supply •
IND Industrial Services
Supply
•
PROC Industriai Process
Supply
GWR Groundwater Recharge
FRSH Freshwater
Replenishment
Reference: RWQCB (1994).
Water Quality Smdy
March 24, 1997
Page 9
1330-02
TABLE 3
BENEFICIAL USES FOR
GROUNDWATER
HSA
4.51
MUN Municipal and Domestic
Supply
•
AGR Agriculmral 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
TABLE 4
GROUNDWATER QUALITY OBJECTIVES
HA 4.50
Total Dissolved Solids 3,500 mg/l
Chloride 800 mg/l
Sulfate 500 mg/I
Sodium (percent) 60
Nitrate 45 mg/l
Iron 0.3 mg/l
Manganese 0.05 mg/l
Methylene Blue Active Substances (MBAS) 0.5 mg/l
Boron 2.0 gm/1
Odor None
Turbidity 5 NTU
Color 15 units
Fluoride 1.0 mg/l
Notes:
The water quality objectives do not apply westerly of the easterly boundary of Interstate Highway
5. The water quality objeaives 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 boundaiy 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 10
1330-02
II 11 II II II 11 i; II II II 11 11 II II 11 ffl ii I I I
TABLE 6
HISTORIC WATER QUALITY DATA
Weli
No.
12S/
Date Temp.
(OF)
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/l 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 manufactured cut and fills. The maximum height of cut slope is
estimated to be about 50 feet and the maxmium 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. Luniting 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 poUutants.
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 tiie amount of the current paved area. Increases in surface mnoff
and poUutant 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 California 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 esthnate 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 acmal 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 quaUty
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 quaUty 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
EXPECTED INCREASE IN SELECTED POLLUTANTS
Constiment Existing
Concentration
(mg/l)
Possible
Future
Concentration
(mg/l)
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 5!^
IMI TABLE 7
WATER QUALITY OF SELECTED RIVERS
Constiment San Dieguito River'
(mg/l)
Escondido Creek^
(mg/l)
— Dissolved Solids 1120 1240
•mm Sodium 130 220
— Calcium 96 84
Magnesium 38 61
I"" Chloride 130 330
Sulfate 290 270
Alkalinity 167
Boron 170
mm Reference
1 Izbicki (1983).
2 Woolfenden (1989).
Water Quality Smdy
March 24, 1997 Page 14
1330-02
Waters identified as having as "munitipal and domestic supply" should meet the water quaUty
limitatiQQshi Table 8 as well as^e groundwater quality objectives (Table 4). Table 8
represents a^rtial listing Of Ulewater 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 unpossible to eliminate from surface
mnoff.
Water Quality Smdy Page 15
March 24, 1997 1330-02
TABLE 8
PARTLVL LISTING OF DOMESTIC WATER QUALITY
LIMITATIONS
Constiment Primary
(mg/l)
Secondary (mg/I)
Constiment Primary
(mg/l) Recommended Upper
Limit
Inorganic Cheniical
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 Smdy
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 quaUty limitations; there is no groundwater quaUty objective. It may
be unpossible to mitigate lead loads.
6.1 SURFACE WATER
The storm water mnoff to San Marcos Creek would be regulated by the General Constmction
Activity Pennit 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 sunilar 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 dismrbance 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 ftirther degrade the surface water quaUty. The 24-hour storm event with
a 25-year remm interval is expected to produce a mnoff volume ofO.37 cfsfor each 855 feet
of roadway (see Appendix A). The expected mnoff from dieJe^^fof theli™ roadway in this
project would produce a flow of approximately 1.53 cft^wIuch|msmall/^ij]^mson with the 25-
year flood flow of 4,500 cfs. The storm water mnoff volum^js^OrOS^percent of the 25-year
flood flow.
6.2 GROUNDWATER
The only constiment present in groundwater identified by the Racm (1982) smdy that may be
of concern 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/l 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/l.
Water Quality Smdy 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, Unes 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 Planfor 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, Califomia.
Geocon, Inc. (1990). Supplemental Soil arui Geologic Investigation for Rancho Santa Fe
Road Realignment, Carlsbad, California. January.
Goodridge, J.D., etal. (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, arui 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, California. Water-Resources Investigations Report 88-4223.
Water Quality Smdy Page 19
March 25, 1997 1330-02
APPENDIX
CALCULATIONS
I
T. (2
]
]
]
]
CoP •=• oto T.?
TlCtO * ISO + 0.00341- CAtDT) TvCiJ •= T0TAT_ KJeL-OArtL. KJIT^£O&£AJ
-r
trJeiL-fei-* OAiuy T/t-*-f PIC-
TIL'S^ foT<n. l2)£S^0u C •• T*
up. i -TbPro.fcS C-ri^-")
(P frt>T >5o, i>'=*0
5 L-froc* t'i'' tf-^i-^^
S.O
ueofrTH Must C^.X't^Sto) ' $c.t^ ^e^Ai.
DUDEK &
ASSOCIATES, INC.
PROJECT: ^Pfco Rgfen,\£.KlKe*^T
BY DATE V'^^ /l? CHKD BY DATE
10x10
JOBNO. \^3o-o^
SHEET OF ^
]'
iC'^i.^.i^-) .--5
tr
- -^VT. t+e> ^
5^ • s^,^f o ^
10x10
- DUDEK & PROJECT: f2-^F (Rjfep ^AvxfutJ u£iJt JOB NO. PSo-oa.
••ASSOCIATES, INC. BY DATsVpn/^f CHKDBY DATE SHEET ^ OF ^
= ITS ^
- 10x10
DUDEK & PROJECT: R^f KOAt fVtf't'^^*^ tft^^ JOB NO.^^^g'C^
ASSOCIATES, INC. BY VAA DATE V'^/'lf CHKDBY DATE SHEET 3 o?3z-
]
4.^^1>^c7.iisr- USB ^ ^r^^
^ 10x10
^DUDEK & PROJECT: l?-^F tot^ pe/^i^j^He^n JOB NO. I3^O-P2.
«. ASSOCIATES, INC. L ^^^^ ykJe^^ CHKD BY DATE SHEET ^ OF±_
"^^
PI
ri
H •m fl m n
STATION MO.
ELtV SEC T-P ONS LOT L*TITijOE LONOlTuDt ^OUHTT
ZS IDS BJC 1 U.4]l
H TtARs IC
2 2.03
-6 ].ie
10 3.IS
20 *.S0
25
•*o 5.2»
SO S.5J
IOO ».22
2«0
1000 I.SD leooD U.T*
PHP 19.56
MEAN 2.12b
.ZD
Z."
• .1*
•s.is
6.12
b.«2
7.06
1.36
6,10
11.IT
U.19
26.62
30
2.»5
*.62 5. ao
6. »3
T.30
• .OS
• .*a
9.So
10.SO
13.06
U.ST
10.38
40 90 «D •o
3.13 3.SS 3.SB 1.93
t.90 5.23 5.-55 6.06
O.IS 6.S3 6.84 T.68
1.3* T.TT a.n 8,83
T.I* 6.16 O.ST 9.25
• ,S* B.96 ».*0 lo.iz
6.9Z «.3T 9,T9 10>53
lo.oo 10.55 10.99 11.T6
11.23 11.TZ IZ.IT 13.01
13.BT 1*.3* 1*.86 J5.T»
n.so 18,1* It.61 19,66
12.ZS 3*.10 3S.0S 18.86
100
*.2Z
6.**
T,«0
9,ZT
9,T(
U,SB
10.99
12. Z*
13. *T
16.I*
ZO.BT
*0.6B
150
4.81
T,3S
9.01
10.ST
11.06
12,06
12.53
13.97
15.37
18,93
2Z.91
46.43
CLOCK MP, COR.
REftlQNAL SKEW
SKE* yseo
KUNTOSIS
N
(tECOKD TEAR
BCCORO HA«I»»UK
NORMALIZED HAX
CALC. cotr, VAR
RC9N. COEF. VAR
USED COEF, VAR
MEAN/A
RPJO/A
RPZS/A
RP90/A
RPie6/A
ptpnoi/*
RPioeoA/A
PRP/A
1:15S
1.600
1.6O0
S.543
67
1927
S.960
2.950
.530
.49* .494
• 1410
.2336
.2917
.33*7
.1771
,5152
• •509
1.1860
3.DS1 3.406 3.616
\'Ml I.soo 1.600 1.600
1.500 1 .600 1.600
5.!47 T,145 T,B23
67 67 67
I92T 192T 1927
S.o90 4.820 10.730
3,169 3.49T 3.4T1
.SZl .539 .56T
.SIS .SZ8 .528
.SIS .520 .518
.1850 ,2065 ,2192
.3119
.3893
,4462
.502Z
,6834
.3514
.4423
.S09S
,STS9
,T9;o
•8605 1,00*3
1.6137 1.8418
.3T30 .4695
.5409
.6113
,8408
1.0662
1.9S53
3.B3S
VMi
I,500
l.SoO
7,444
6T
192Z
1Z<160
S.T32
.SB2
,526
.5Z6
.2325
.3956
.49*0
,S68I
,6399
,»Tz7
I'lOOl 2.OOTI
4,060
wni
1,*00
l.*O0
6,9]4
67
1922
12.160
3.520
,565
.522
,522
.2*62
.4)79
.5195
.5936
.6665
.9008
1,1284
2.1T3S
4.4B8
i.3oa
1 ,300
10.903
67
19Z2
17.160
4.813
.601
.521
.521
.2673
.493T
.5606
,6186
,T144
.95T3
1,1918
2,3560
*.666 5.3*0
1 .00ft Z,3*9
1,200
1,200
11.25)
67
1922
18.30(1
4.886
.598
• SIZ
.512
,2841
.4791
,5070
.6662
.7423
.9846
l,2l7o
2.4662
1,Z0D
1.200
9.812
6T
1922
19.660
4,446
.612
.513
.513
,3237
.5464
.6704
.TS99
,8468
1,1234
1.3867
Z.8149
200
9,32
8.03
9.77
11,3<
11,90
12.14
13,42
14.88
16,32
19,S3
23,96
49.TT
5,846
1.100
1.100
9.903
»7
1922
21.860
4.498
,61S
.901
.501
.3544
.5925
.T212
.6133
.902*
1.1842
I**S2S
3.OITT
300
•6.21
9.20
11,10
12.84
13.38
14.48
19.00
16,56 IB,of
21,44
26,o8
59.42
OOD
8,36
12.47
15.67
17.47
10.21
19.73
20.44
22.58
24,66
29,32
35.68
74.05
e.T47 9,091
1 .000
I ,000
T,T20
67
1422
21.860
4.092
.9*7
.481
.481
,4090
,6727
,8109
.9092
1.003T
1.3009
1.9810
3,3602
i;5S!
1 ,000
i ,000
9.S26
67
1422
29.680
1,661
.498
,491
.441
3650
19.26
21,61
25.69
29,49
30-6T
31,25
34.23
ST.bT
4) .03
48.S6
58.9 3
114,*2
16.444
':!ss
1.100
1.100
4.132
TO
1922
38.230
3.3eT
,384
.416
,416
.5512
.4139
1.1040
1.2391
1.3641
1.7T74
2.1632
4,6105
l.OOOO
1.5578
1,8943
2.0TS3
2.21*0
1,9442
3.STZ9
7,2400
STATION N*HE STATION NO,
•SM ORDCR SUB
Z86 Z840 I % «SCBV01fl
PRECIPITATION DEPTM-DURATION-FREflUCNCY TABLE
ELEV Ste T"P RNO LOT LATITUDE LONOITuOE COuNTY
COOE
3T3 TS2 16 IIS 03M S 33.217 11T,21T 90
HAXIHUH PRECIPITATION FOR INDICATED DURATION D-OATS M-HOURS
URN PERIOD 20 IN TEARS ID 20
Z 1 88 Z,Z7
9 2 •7 3.51
18 3 57 4.37
20 4 J* 5.20
Z9 4 46 5,*6
40 4 90 6,00
50 9 ,11 6.Z5
100 5 .76 7,0*
-200 6 • 40 7,81
itee 7 ,07 9,90
10800 9 ,94 12.06
PNP 18 •IZ Z2.62
3D
,44
^. Hi AN
- CLOCK NR. COR.
CALCULATED WE«
REGIONAL iKEK
SKEH USED
KuRTOSlS
N
RECORD TEAR
IICCORD HAXI^UH
NORMALIZED MAX
CALC, COEF. VAR
REIN, COEF. VAR
UttO COtF, VAR
MEAN/A
RP'IOM
B^2S/*
RPSO/A
RPlOO'"^
RPl8«»/»
Rpieooe/A
2,1S4
1.140
.TS2
1.600
1,600
3,462
32
1941
3.820
z.oze
.381
,*44
,444
.1682
.2786
.34T9
.3991
.4497
.6144
.7T62
li*l*5
2.592
l.OTO
,304
1,500
1,500
2.865
32
14*1
4.380
1.832
.3T6
,sis
• SIS
2.
3,82
..T9
5.71
6,01
6.65
6,44
7,04
8,7«
10,79
13.68
2S.09
2.013
1 .0*0
-0.032
1 .600
1 .600
2.265
32
1441
4.380
i.ses
,370
.528
.SZ8
4D
2.5*
3.98
*,99
5.47
6,28
6,93
7,24
8.18
9.11
11,25
14.27
26.iT
2.934
1.020
.236
1.600
1.600
SD
2.6T
*.1T
5,20
6,l9
6.51
7,16
7,47
8,41
9,34
11,4?
14.46
2T,lT
3-057
i.eio
.360
i.seo
I'SOO
6D
2.83
A.ie
5,44
6.44
6.76
7,42
7,T2
• ,6T
9,60
11,72
14.60
28.2T
3.202
l.OlO
.*16
1 ,480
1,*00
80
2.95
4,55
5.62
6,63
6.95
7,61
7,91
8.85
9.TT
11,86
14.7T
29.20
lOD 150 20D
3.33 3.70 4,10
5.09 5,66 6.19
6,2s 6.94 7.53
7.33 8,14 8.78
7,67 8.91 4.17
8.36 9.29 9.36
0,64 9,65 10.3*
9.68 10.TS 11.48
10.65 11.83 12.98
12.84 14,26 15.86
IS.IT 17.63 11,«T
32,16 •35.74 38.38
2.718 2,938 2,780
32 32 32
1938 1931 1936
9.390 5.Too 9.920
2,156 2.315 2.2*0
,302 ,3T0 ,3Te
.526 .526 • 522
,92" ,S2t .522
.202*
• 3413 ,4260
• 4803
.5445
.T»T8
.4416
^•T65T
.2196
.ITJT
,4T04
,5419
• 6125
,8*24
I.06B2
1,9584
.2291
.3898
.4406
• 5652
,6388
,8T86
1.11*1
2.0431
.2386
.4060
.5080
.9830
.696T
,8959
1,1289
2.121*
.2500
• 4244
.92T6
,6031
,6T69
.9149
1.1461
2.20T4
3.312
1,000
.390
1.300
1 ,300
2.6OZ
32
1950
9.920
2.102
.3T9
.921
• 921
• 2586
.4390
,9426
.6174
.6912
.9262
1,1532
2,2795
1.705
1.000
,3TB
1.200
1.200
2,438
32
196S
6.*oa
1,881
,387
.512
.912
.2893
,4876
.5484
.6782
.T5ST
1.8B2*
1,2390
2.5188
4.111
1.000
.360
1 .200
1,200
2.488
32
1430
7,* 30
2.037
.396
.513
.913
.3209
.9*16
,6666
,T533
.139.
1,1136
N3747
2,7405
.5oT
iODO
• 198
,100
,100
300
4.94
7.32
8,83
10,21
10,6*
11,52
11.93
13.17
14,37
17,06
20,7*
44.0?
9,366
1,000
.261
1,000
1,000
600
6,86
10.24
12.3T
14.3*
14.45
16.20
16,T8
18,54
20,29
24, BT
19.29
62*43
T.683
I ,000
,679
i ,000
i.ooo
3690
li,89
16.T8
14,99
22,90
23.82
24.26
26,58
24.25
31.86
3T,T1
49,T6
»2.73
12.888
1,400
1,112
1,100
1,100
2.314 2,760 3.206 4.921
32 32 32 32
1938 1441 1941 >"I 7.500 4,570 14.430 26.470
1.737 1,916 2.304 2,973
.382 .399 .43* ,414
,*!» .501 .481 .441
,414
,*!» ,501 .481 ,491 ,416
.3519
.5883
,Tl60
>8oT5 .89eo i.lTST
1,44(2
2,"82
.4184
.6890
,8306
.9312
1.0280
1.3320
l,6l93
3,6416
.»82«
.*66l
1.1678
1.1699
1.44T3
1,8T89
2.2868
4.8T34
l.OOOB
l.SSTI
1,8593
2.0T93
2.?840
2,9442
3,9T29
T,240a
PEARSON TTPE in OlSTBUUTION USED
PROBABLE HAXIMUtI PRECIPITATION ESTIHATE BASED ON 15
HNERE N IS SHALL BE8ULTS ARE NOT DEPENDABLE
369
STANDARD DEVIATIONS
1 f
— LEGEND —
, PRECIPITATION STATION LOCATION
}Z«» STATION NUMBER
( OAiLT )
June 1976 •I
I I
FIGURES
. J SanMarcoa. \ r- Park V. '
• . / •• -'/- .-.../'X ''•3''^' ;! 15- *fi Par.