Why do we need to model theLower Passaic – Newark Bay?

Ed Garland1, Eugenia Naranjo2

1- HDR|HydroQual 2-USEPA

December 19, 2011

Models1. Why do we need them?

– For sediment sites, for Passaic2. What are they doing?3. Why does modeling take so long?3. Why does modeling take so long?4. Initial results of Lower Passaic Modeling

study

CARPModelGrid

16,000 water

A model is a schematic

16,000 water column

and 16,000sediment cells

• Future Conditions• Impact of Extreme Events• How would Newark Bay

sediment affect the remediated Passaic?

With a model we can:

PREDICTremediated Passaic?

• Impact of a storm on a ‘cap’

EVALUATE&ASSESS

• effects of “no-action” and “complete removal or other remediation alternatives• How resuspension from dredging might affect Newark Bay

Sampling Locations vs ModelIt’s not possible to measure everything

Data Collected with

Moored Instruments

What if we don’t use a model?• We would not be able to show what be

may achieved after millions of $$ are spent

• We would not be able to predict what would happen to the environment if we would happen to the environment if we do nothing

• All of this uncertainty increases the likelihood that the clean-up plan will be challenged in court

Modeling FrameworkHydrodynamics

Sediment Transport

WATER movement

Particles movement

Risk Assessment

Contaminant Transport & Fate

RCATOX

Contaminants attached to particles

Passaic,Passaic,Hackensack,Hackensack,Newark Bay,Newark Bay,

NYNY--NJ HarborNJ Harbor

Sediment Transport Sediment Transport 44 x 24344 x 243

(10,692 grid cells)(10,692 grid cells)Top Active zone Top Active zone Top Active zone Top Active zone

divided into 10 layersdivided into 10 layers

A partially mixed estuary

based on Dyer, 1972; Pethick, 1984

Low River Flow

Newark BayDundee DamRange of Salinity

Front Location

Erosion and Deposition (Mixing) of Material

Due to Estuarine Processes

Lower Energy Region – Less Erosion and

Deposition

Estuarine Exchange

Low Flow Input from Passaic River

with Newark Bay

from Passaic River Downstream Transport of

River Material

Net Upstream Transport of Bay

Material

Physical Water Column Physical Water Column Monitoring Period Monitoring Period

Model Data ComparisonsModel Data ComparisonsModel Data ComparisonsModel Data Comparisons

Movement of Salt Front

SHOW SALINITY SALINITY MOVIE

Depth_TSS_Salt.exe

March 2010 High Flow: March 2010 High Flow: Comparing model results to dataComparing model results to dataComparing model results to dataComparing model results to data

Sediment Bed Elevation Changes:Sediment Bed Elevation Changes:Comparing model results to dataComparing model results to dataComparing model results to dataComparing model results to data

3) Why does it take so long• To correctly develop and apply a model is time

consuming• A model is not reality, the modeler is trying to

reproduce what is happening in the real world– Model calibration– Needs to understand the data– Needs to understand the data– Create a or understanding of the system with the data– Needs to “translate” data into “model language– Long process

Despite super fast computers, heavy computations per grid/layer

We are making long term calculations/predictions

Now what?How does this information get transferred?

Hydrodynamic Model Sediment Transport Model Contaminant Fate Model

Information TransferFlow Sediments

Organic Carbon

Chemical Loads

TidesCurrent Velocity

Salinity

Suspended Solids Concentration

Deposition Scour

Burial

Particulate andDissolvedChemical

Concentrations

Part and DissChemical

Concentrations

Sediment Bed

QUESTIONS