Water Quality 1 - Virginia Lakes and Watersheds Association

SESSION 3D
WATER Q UALITY 1
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1D & 1D/2D MODELING APPROACHES TO EVALUATE FLOODING WITHIN THE
CITY OF NEWPORT NEWS, VIRGINIA
Steve Godfrey, 1 PE, CFM, Woolpert; David Powell, 2 Ph.D., PE, Woolpert; Jamie Clark, 3 PE,
City of Newport News
Many urban stormwater conveyance systems across the country were installed over 50 years
ago, and newer development has overtaxed these aging systems. A project-centric view of
localized stormwater issues sometimes solved one problem but inadvertently created another.
In coastal Virginia, drainage systems at or below sea level, flood control structures, tidal
patterns, and multiple outlets for floodwaters must be incorporated into the analysis. All of
these factors lead to increasingly complex patterns that must be analyzed using hydrologic and
hydraulic models.
Over the past few years, the neighborhoods along Newmarket Creek in the City of Newport
News, VA have experienced several large flooding events in addition to nuisance flooding. In
this presentation, the team will use Newport News’ situation to share some unique modeling
techniques and solutions to alleviate the flooding in neighborhoods along Newmarket Creek.
The engineering team developed both XP-SWMM 1D and 1D/2D models to identify areas of
potential flooding, determine the level of service (LOS) of the existing drainage systems, and
evaluate feasible improvement alternatives. Existing HEC-RAS and HEC-HMS models of the
riverine system were incorporated into a fully dynamic model of open and closed conveyance
systems extending upstream into the floodplains and beyond. This created a challenge when
evaluating the different responses between the existing steady-state riverine model with the
new dynamic open and closed system models.
This presentation will help participants evaluate 1D and 1D/2D modeling approaches and results
of the same area. It will also show participants some of the advanced modeling techniques used
to simulate dual systems inside and outside of the floodplain. The challenges of finding
solutions for middle sections of a stream flowing between jurisdictions will be addressed, and
unique solutions to this urban flooding problem will be discussed.
1
Modeling Team Leader, Vice President; 11301 Carmel Commons Blvd, Suite 300, Charlotte, NC 28226;
704-526-3048; [email protected]
2
Engineer; 676 Independence Parkway, Suite 100, Chesapeake, VA 23320; 757-549-5382;
[email protected]
3
Engineer III, Civil Design Division; 2400 Washington Avenue, Newport News, VA 23607; 757-926-8655;
[email protected]
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RELATIVE SENSITIVITY ANALYSIS OF THE LAGRANGIAN MODEL FOR
SIMULATING HORIZONTAL SUBMERGED BUOYANT JET PLUME IN THE
STAGNANT AMBIENT FOR EFFLUENT DISCHARGE
Arash Aliabadi Farahani, 1 Old Dominion University; Matthew Elliott,2 Old Dominion
University; Jaewan Yoon, 3 Old Dominion University
Increase in population leads to an increase in industrial, municipal, agricultural and domestic
effluents discharged into different water bodies including streams, rivers, lakes, reservoirs,
estuaries and coastal waters. Liquid wastes such as hot water from cooling of thermal power
plants, as well as the effluent from wastewater treatment plants, are usually disposed by means
of submerged outfalls at the coast near the plant site. It is noted that all aqueous discharges in
the United States are subject to federal, state and local regulation, and the water quality criteria
must be met at the edge of a mixing zone, which is an allocated impact zone where water
quality criteria can be exceeded as long as acutely toxic conditions are prevented.
Mathematical models developed for prediction of the characteristics of submerged buoyant jets
are categorized into three general groups: (a) length scale, (b) numerical and (c) integral
methods. In length scale method, the flow is divided into different regimes, each dominated by
particular flow properties. In numerical models, a system of Reynolds equations is solved within
finite element or finite difference approach. This numerical method is not frequently applied in
routine engineering application, mostly due to procedural difficulties in specification of
boundary conditions and all term of turbulent transport. Au contraire, integral models are
simpler, versatile and popular tools for prediction of discharge mixing by using a set of ordinary
differential equations derived from the cross-sectional integration of jet-properties such as
mass, momentum, and buoyancy fluxes.
These three predictive models are largely described by two different approaches - Eulerian and
Lagrangian formulations. Eulerian model analyzes a fixed volume that is divided into a matrix
and uses differential equations to determine source and sink fluxes interfacing the volume. In a
Lagrangian approach, the model follows a collection of moving particles and monitors changes
in their properties in relation to time so that is a more efficient way to sample a fluid flow and
the physical conservation laws that are inherently Lagrangian since they apply to moving fluid
volumes rather than to the fluid that happens to be present at pre-fixed topology in space.
In this study, univariate relative sensitivity analysis of Lagrangian model parameters prediting
submerged buoyant jet plume in the stagnant ambient for effluent discharge was conducted to
identify key model-parameters significantly influencing the model response. Relative sensitivity
analysis assumed that the forced entrainment (∆MF) which is proportional to ambient velocity
(Ua) is zero to represent a stagnant ambient condition. Findings from the sensitivity analysis will
be used to reduce the complexity of the model as well as to further reduce computational
1
Graduate student, PhDCEE Program, Department Civil and Environmental Engineering; Kaufman Hall
135, Norfolk, VA 23529; 757-683-4724; [email protected]
2
Graduate student, Environmental Engineering Master Program; Department Civil and Environmental
Engineering; Kaufman Hall 135, Norfolk, VA 23529; 757-683-4724; [email protected]
3
Associate Professor, Department Civil and Environmental Engineering; Kaufman Hall 135, Norfolk, VA
23529; 757-683-4724; [email protected]
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redundancy in the Lagrangian model for predicting submerged buoyant jet plume flux of
effluent discharge.
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IN-SITU TOTAL SUSPENDED SOLIDS (TSS) CHARACTERIZATION USING
FORMAZIN ATTENUATION UNIT (FAU)-BASED DISJOINTED GENERAL LINEAR
MODEL
Jeremy Pianalto, 1 Old Dominion University; Robert Redmond, 2 Old Dominion University;
Jaewan Yoon, 3 Old Dominion University
During dredging operations, real time monitoring of total suspended solids (TSS) in the ambient
water becomes more of a priority. Afterward, dredge spoils will be placed to Confined Disposal
Facilities (CDF’s). During the early stages of confinement, suspended solids from the spoils are
settled out hydraulically with given travel length of the confined area and time, to ensure water
quality of CDF’s effluent discharge to the receiving body of water will be safe. The effluent
water quality must meet federal contractual requirements to avoid public perception of
contamination as well as avoiding environmental impacts. This is an establishing water quality
management strategy for TSS.
For monitoring TSS levels in CDF’s, the Environmental Protection Agency (EPA) has an approved
method, EPA Method 160.2 which measures TSS by filtration of a sample, drying of sediment
material on the filter, and using gravimetric methods to quantify sample TSS. This method takes
time to collect, retrieve, send to the lab, filter, dry, and record and report. Thus the temporal
lapse between sampling and final quantification of TSS could be a problem when potentially
dangerous levels of TSS could be allow to be introduced into the receiving body. A real time
solution would facilitate a real-time TSS quantification and monitoring so that possible TSS
problem can be rectified immediately.
In this study, an alternative method of estimating TSS was developed to obviate problems in
current gravimetric TSS procedure by utilizing colorimeteric Formazin Attenuation Unit (FAU)
approach which would facilitate diminutive wait intervals, portability of equipment, and
simplicity of method. Historical and new 175 TSS samples, both gravimetric and colorimeteric
measurements over a period of six months, from the Craney Island Dredged Material
Management Area (CIDMMA) managed by the Operations Branch, Norfolk District, US Army
Corps of Engineers (USACE) were used in this study to develop a in-situ TSS characteristic model
with operational confidence intervals by using Univariate Disjointed General Linear Model
technique.
1
Graduate student, Environmental Engineering Master Program, Department Civil and Environmental
Engineering; Kaufman Hall 135, Norfolk, VA 23529; 757-683-4724; [email protected]
2
Graduate student, Environmental Engineering Master Program, Department Civil and Environmental
Engineering; Kaufman Hall 135, Norfolk, VA 23529; 757-683-4724; [email protected]
3
Associate Professor, Department Civil and Environmental Engineering; Kaufman Hall 135, Norfolk, VA
23529; 757-683-4724; [email protected]
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UNDERSTANDING VRRM COMPLIANCE SPREADSHEETS
Partha Sarathi, 1 PE, ENSOFTEC
To prevent harmful pollutants from stormwater runoff being discharged into a Municipal
Separate Storm Sewer Systems (MS4s), operators must obtain a NPDES permit and develop a
stormwater management program before any land disturbance activity can begin. The Virginia
Department of Environmental Quality (DEQ) has put in place the new Virginia Stormwater
Management Program {VSMP) Permit Regulations which became effective from July 2014.
Localities are authorized to adopt their own stormwater management ordinances as long as
these ordinances are based upon findings of local or regional comprehensive watershed
management studies or findings developed through the implementation of a MS4 permit or are
determined to be necessary to prevent any further degradation to water resources or to address
specific existing water pollution. Some projects already in the pipeline are ‘grand-fathered’
from these requirements until July 2019. These regulations and ordinances will require a
change in the mindset of the “permittee.”
In order to help designers and plan reviewers to evaluate the implementation of BMPs on a
given site and verify compliance with the local and/or State stormwater requirements, the DEQ
has provided two Virginia Runoff Reduction Method (VRRM) Compliance Spreadsheets. Chapter
12 of the Virginia Stormwater Management Handbook, 2013 (Draft) gives the User’s Guide &
Documentation for these two spreadsheets, their use, and limitations.
This paper highlights several aspects that the designers and reviewers will need to keep in mind
while using the VRRM Compliance Spreadsheets for calculating runoff reduction and pollutant
load reduction volumes for land disturbance projects. The paper also presents some example
projects.
1
President; 15, Rolling Green Court, North Potomac, MD 20878; 301-294-7066; [email protected]
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