Dominguez Channel and Los Dominguez Channel and Los Angeles and - - PowerPoint PPT Presentation

Dominguez Channel and Los Dominguez Channel and Los Angeles and Long Beach Harbors Angeles and Long Beach Harbors TMDLs TMDLs Nearshore Nearshore Modeling Options Modeling Options

Stephen Carter, Tetra Tech, Inc. Stephen Carter, Tetra Tech, Inc.

Technical Advisory Committee Meeting Technical Advisory Committee Meeting May 9, 2006 May 9, 2006

Watershed Model Development

• Models developed to provide estimates of

historic (hourly/daily) pollutant loadings to receiving waters

• Pollutants addressed in TMDL and requiring

model development

– Metals (Cu, Pb, Zn) – PAHs – DDT – Chlordane – PCBs

• Separate approaches required for dry and wet

weather

– Sources and methods of transport vary – Availability of data characterizing water quality for each condition

Overview of Watersheds Addressed

Wet-Weather Watershed Model Development

• LA River (LAR) and San Gabriel River (SGR)

– Previous models developed by Tetra Tech to support watershed TMDLs – Models setup for hydrology, sediment, and metals (Cu, Pb, & Zn)

• Dominguez Channel (DC)

– Model currently under development by SCCWRP – Models setup for hydrology, sediment, and metals (Cu, Pb, & Zn)

• Nearshore watersheds

– Continuation of regional modeling approach used for LAR, SGR, and DC – Models currently under development by Tetra Tech

• New approaches required for modeling PAHs, DDT,

chlordane, and PCBs

Model Development of Nearshore Areas

• Delineations

based on DEMs and data received from POLA and POLB

Consideration of Local Monitoring Stations

• Monitoring data

collected by POLA and POLB

• Three sites in

nearshore model domain

– Maritime Museum (MM) – Pier A – Forest

• Pier A and Forest

sites represent “Port Activities” based on SCAG land use data

• MM represents a

mix of land uses

Regional Modeling Approach for Sediment and Metals

• Erosion is a function of land use activity, soil characteristics,

slope, land cover, and precipitation

• Erosion occurs due to rainfall “energy”

– Detachment of soil particles – Wash off of detached material – Use of potency factors to estimate associated metals

• Model parameters developed by SCCWRP for major land use

categories

• Validated in separate watershed models

– Ballona Creek HSPF model – SCCWRP – LAR and SGR LSPC models – Tetra Tech

Raindrop impact detaches soil particles

Refinement of the Regional Modeling Approach

• Additional land use

category added to model – Port Activities

• POLA and POLB data used

for calibration of parameters specific to Port Activities

• Example: Forest site

– Flow – Sediment

1 2 3 4 5 6 2/24/03 12:00 2/25/03 0:00 2/25/03 12:00

Flow (cfs)

Modeled Measured

100 200 300 400 500 600 2/24/03 12:00 2/25/03 0:00 2/25/03 12:00

TSS (mg/L)

Modeled Measured

Refinement of the Regional Modeling Approach (cont’d)

• Following hydrology and

sediment, metals modeling parameters were calibrated

• Figures show

comparisons of observed and model-predicted concentrations for the Forest site

0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.20 2/24/03 12:00 2/24/03 18:00 2/25/03 0:00 2/25/03 6:00 2/25/03 12:00

Copper Concentration (mg/L)

Modeled Measured 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 2/24/03 12:00 2/24/03 18:00 2/25/03 0:00 2/25/03 6:00 2/25/03 12:00

Lead Concentration (mg/L)

Modeled Measured 0.00 0.20 0.40 0.60 0.80 1.00 1.20 2/24/03 12:00 2/24/03 18:00 2/25/03 0:00 2/25/03 6:00 2/25/03 12:00

Zinc Concentrations (mg/L)

Modeled Measured

Refinement of the Regional Modeling Approach (cont’d)

• Figures show

comparisons of observed and model-predicted loads for the Forest site

200 400 600 800 1,000 1,200 2/24/03 12:00 2/24/03 18:00 2/25/03 0:00 2/25/03 6:00 2/25/03 12:00

Copper Load (g/day)

Modeled Measured 200 400 600 800 1,000 1,200 1,400 2/24/03 12:00 2/24/03 18:00 2/25/03 0:00 2/25/03 6:00 2/25/03 12:00

Lead Load (g/day)

Modeled Measured 2,000 4,000 6,000 8,000 10,000 12,000 2/24/03 12:00 2/24/03 18:00 2/25/03 0:00 2/25/03 6:00 2/25/03 12:00

Zinc Load (g/day)

Modeled Measured

Wet-weather Modeling Approach for PAHs

• EMCs for PAHs reported by SCCWRP for various land uses

based on monitoring performed in the LA Region (Stein et al., 2005)

Land Use EMC (ng/L) SD Industrial 1.50E+03 8.60E+02 Commercial 1.20E+03 5.80E+02 Low-density residential 1.40E+03 6.00E+02 High-density residential 4.40E+03 2.60E+03 Agricultural 8.60E+02 1.00E+03 Open 1.38E+02 0.00E+00 Recreational 4.60E+02 3.00E+02 Transportation 4.80E+02 2.80E+02

Wet-weather Modeling Approach for PAHs

• Total PAH concentrations for each model subwatershed

predicted using weighted averages of land use EMCs based on area and runoff potential of each land use in each subwatershed where, EMCavg = average subwatershed EMC; LU = land use category; A = land use area; C = runoff coefficient EMC A C EMC A C

avg i i i i LU i i i LU

. ( ) =

= =

∑ ∑

Example Results for PAHs – Forest Site

• Dynamic hydrology based
• n LSPC model
• Constant PAH

concentration based on weighted EMCs

– Predicted ranges consistent with observed – EMCs cannot account for first flush

• Resulting in dynamic

loads due to variable flows

0.0 1.0 2.0 3.0 4.0 5.0 6.0 2/24/03 0:00 2/24/03 12:00 2/25/03 0:00 2/25/03 12:00 2/26/03 0:00

Flow (cfs) Flow

1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000 2/24/03 0:00 2/24/03 12:00 2/25/03 0:00 2/25/03 12:00 2/26/03 0:00

PAH Concentration (ng/L)

EMC (-SD) EMC (Mean) EMC (+SD) Measured 5 10 15 20 25 30 35 2/24/03 0:00 2/24/03 12:00 2/25/03 0:00 2/25/03 12:00 2/26/03 0:00

PAH Load (g/day) Load (Low Range) Load (Mean) Load (High Range)

Wet-weather Monitoring Data for DDT, chlordane, and PCBs

• Limited data from LADPW watershed monitoring due

to high detection limits (DL)

– Few detectable levels of DDT (4,4'-DDD, 4,4'-DDE, and 4,4'- DDT, each with a DL of 0.1 ug/L) – No detectable levels of PCBs (DL = 0.05 ug/L) – No detectable levels chlordane (DL = 0.5 ug/L)

• Additional monitoring at POLA/POLB sites at lower

DLs (0.001 ug/L)

– Representative of land uses surrounding the ports – Does not provide information for all land uses

Wet-weather Modeling Approach for DDT, chlordane, and PCBs

• Lack of water quality data to base watershed loading

assumptions

• Sediment quality data can provide estimates of

pollutants transported with sediment

– Bight 03 data most representative of latest conditions

• Assumes that concentrations in bottom sediments are

representative of sediment concentrations transported from watersheds during wet-weather

Wet-weather Modeling Approach for DDT, chlordane, and PCBs

• Lack of water quality data to base watershed loading

assumptions

• Sediment quality data can provide estimates of

pollutants transported with sediment

– Bight 03 data most representative of latest conditions

• Assumes that concentrations in bottom sediments are

representative of sediment concentrations transported from watersheds during wet-weather

Bight 03 Sediment DDT Data

Bight 03 Sediment PCB Data

Bight 03 Sediment Chlordane Data

Wet-weather Modeling Approach for DDT, chlordane, and PCBs (cont’d)

Pollutant

• Conc. in Sediment

(ug/kg) Modeled Wet Weather TSS Concentration (mg/L) Conversion factor Water Quality Pollutant Concentration (ug/L)

x x =

• Sediment concentrations assigned to each

subwatershed

– Based on proximity to watershed discharge

• Sediment concentrations (ug/L) multiplied by

hourly TSS concentrations (mg/L) predicted by watershed models

• Results in hourly prediction of pollutant

concentration (ug/L) in runoff

Assignment of Bight 03 Stations to Modeled Subwatersheds

Example –DDT, PCB, and Chlordane Loads from the Forest Site

• Sediment concentrations from Bight 03 Station

4210

Pollutant Concentration DDT 24.41 (ug/kg) PCBs 0.38 (ug/kg) Chlordane 0.29 (ug/kg)

Forest 4210

Example –DDT, PCB, and Chlordane Loads from the Forest Site (cont’d)

• All POLA/POLB monitoring

data at Forest were non- detects

• Most resulting pollutant

concentrations were also below DLs

• Although DDT exceeded,

not by much

• Combined with model-

predicted flows, resulted in hourly load predictions

0.0000 0.0002 0.0004 0.0006 0.0008 0.0010 0.0012 2/24/03 0:00 2/24/03 12:00 2/25/03 0:00 2/25/03 12:00

Chlordane Concentration (ug/L)

Modeled Port DL 0.0000 0.0002 0.0004 0.0006 0.0008 0.0010 0.0012 0.0014 0.0016 2/24/03 0:00 2/24/03 12:00 2/25/03 0:00 2/25/03 12:00

Chlordane Load (g/day)

Load 0.000 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.010 2/24/03 0:00 2/24/03 12:00 2/25/03 0:00 2/25/03 12:00

DDT Concentration (ug/L)

Modeled Port DL

0.000 0.020 0.040 0.060 0.080 0.100 0.120 0.140

2/24/03 0:00 2/24/03 12:00 2/25/03 0:00 2/25/03 12:00

DDT Load (g/day)

Load 0.0000 0.0002 0.0004 0.0006 0.0008 0.0010 0.0012 2/24/03 0:00 2/24/03 12:00 2/25/03 0:00 2/25/03 12:00

PCB Concentration (ug/L)

Modeled Port DL

0.0000 0.0002 0.0004 0.0006 0.0008 0.0010 0.0012 0.0014 0.0016 0.0018 0.0020

2/24/03 0:00 2/24/03 12:00 2/25/03 0:00 2/25/03 12:00

PCB Load (g/day)

Load

Dry-Weather Watershed Model Development

• LA River (LAR) and San Gabriel River (SGR)

– Models developed to provide steady-state simulation of flows and metals – Based on detailed dry-weather monitoring data

• Dominguez Channel (DC)

– Monitoring data collected by Everest – no model of DC

• Nearshore watersheds

– Most watersheds do not have data – Requires new approach for prediction of flows and water quality based on data collected in the region

Estimation of Dry-Weather Runoff from Nearshore Areas

• Lack of flow monitoring at most nearshore

subwatersheds

• Dry flows typically associated with urban land use
• SCCWRP reported average flows for six

watersheds monitored in the LA area (Stein and Ackerman, in press)

• Relationship was established for prediction of dry

flows based on total urban area (R2 = 0.96)

• Land use distributions in each model

subwatersheds used to calculate dry flows

Flow UrbanArea

= ×

00024 . ( )

Estimation of Metals Concentrations from Dry-Weather Nearshore Runoff

• Average metals concentrations determined from

LADPW dry-weather monitoring data at ME sites

• Non-detects impacted averages
• Different assumptions for non-detects tested to

determine effect on averages

Value for Non-Detected Samples Metals Values 1/2 Detection Limit Detection Limit Region-wide Concentrations Average Copper Concentration (ug/L) 19.92 20.33 20.74 Average Lead Concentration (ug/L) 1.92 3.31 4.70 Average Zinc Concentration (ug/L) 85.50 95.66 105.83

Dry-weather Modeling Approach for Metals

• Flows estimated for each model subwatershed
• Metals concentrations assigned based on

regional averages Example: Forest Site

Forest Subwatershed Loads Average Copper Load (g/day) 0.66 0.67 0.68 Average Lead Load (g/day) 0.06 0.11 0.16 Average Zinc Load (g/day) 2.82 3.15 3.49

Next Steps

Wet-Weather Modeling

• Refine calibration of metals modeling parameters

based on data collected at Maritime Museum

• Application of the modeling approaches for PAHs,

DDT, chlordane, and PCBs for all watersheds

– Includes neashore areas, LAR, and SGR

Dry-Weather Modeling

• Selection of appropriate assumptions for metals

DLs for calculation of regional averages

• Determination of average metals concentrations

for LAR and SGR

– Based on detailed dry-weather monitoring studies performed by SCCWRP – Consistent with TMDLs for the watersheds