Stormwater Remediation Project

1
Stormwater RemediationProject

• Professor Art McGarity, Zach Eichenwald
• Assisted by Markia Collins, Sophia Richardson,
• Richard Scott, Pete Cosfol

2
The Team (minus Sophie)
3
Little Crum Creek

• Watershed the area from which surface water
  drains into a particular body of water after an
  event (rainfall)

4
An effort in three parts

• Monitor
• Collect and test water samples to represent
  stream quality with data
• Model
• Simulate stream flow and pollutant transport to
  help pinpoint locations for stormwater management
  technology
• Low Impact Development
• Stormwater management technology and practices
  to reduce runoff volume and nonpoint pollution

5
Collecting Samples
6
ISCO Sampler

• Triggered by rain or stream depth, samples at
  certain intervals throughout an event
• Stores flow data
• Velocity
• Depth
• Rainfall
• Flow
• Captures up to 24 samples

7
(No Transcript)
8
Gathering Data
9
Testing for Pollutants

• Nitrates (NO3) and phosphates (PO4)
• Excess plant nutrients cause algae blooms
  (eutrophication) whose decay depletes oxygen
• TSS (Total Suspended Solids)
• Sediments can clog creek beds
• Carry other pollutants, including heavy metals,
  along with it

10
The Tests

• Hach colorimeters quantify pollutant levels by
  the amount of absorbance of light
• In the TSS test solids are filtered from a 100 mL
  sample and weighed to calculate concentration

11
Other Tests and Calculations

• Standard Additions
• Turbidity
• Turbidity vs. TSS
• Pollutant Load- an estimation of the total PO4,
  NO3, and solids flowing throughout a specific
  interval during an event
• L CQ?t
• Event Mean Concentration
• S(CtQt)

S(Qi)
12
Sample Turbidity (fau) TSS (mg/L) NO3 (mg/L) Abs PO4 (mg/L) Abs
A1 18 17 2.1 46.28 0.34 79.7
A2 12 -76 2.1 46.3 1.57 35.24
A3 169 533 0.3 89 0.39 76.93
A4 506 853 0.3 89.08 0.42 75.87
A5 280 490 0.4 86.26 0.47 73.1
A6 142 210 0.9 72.47 0.28 83.18
A7 112 147 0.9 70.87 0.29 82.62
13
The Sonde

• Remotely and continuously monitors
• pH/ORP
• Dissolved oxygen
• Nitrate
• Conductivity
• Temperature
• Turbidity
• Depth

14
(No Transcript)
15
Modeling
16
Why Model?

• We cant observe the entire watershed
• We arent able to observe all possible weather
  events
• The model allows us to see the response of the
  watershed to any possible input, including large
  storm events that occur infrequently
• We can experiment with different development and
  storm water reduction scenarios

17
Modeling the (Big) Watershed

• Previous work StormWISE (StormWater Investment
  Strategy Evaluator)
• Optimization program developed by Professor
  Arthur McGarity
• Uses RUNQUAL (Penn State) to develop water
  quality parameters
• Placement of Best Management Practices (BMPs)
  optimized using linear programming techniques.
• Locations for BMPs are not site specific

18
Zooming in

• Summer work involves developing a more site
  specific version of StormWISE
• Water quality and quality are modeled using EPAs
  SWMM (StormWater Management Model)
• Model will be able to identify site specific
  locations for BMPs and model the effects of
  implementation

19
SWMM

• Dynamic rainfall-runoff simulation
• Can be used for single event or long term
  simulation of storm water runoff quantity and
  quality
• Is used to develop a simulated hydrograph and
  pollutograph given rainfall input
• Can model the transport of Nitrate, Phosphate,
  and TSS

20
The SWMM Model
Subcatchments
21
SWMM Parameters

• SWMM requires (a few) basic parameters about each
  subcatchment, node, and conduit

Subcatchments SCS CN, amount of impervious surface (), slope (), hydraulic length
Nodes Invert elevation, initial depth, maximum depth
Conduits Length, roughness, size, type
22
Basic Hydrology (SWMM uses this!)
Source Louisiana DEQ - http//www.deq.louisiana.g
ov/portal/Default.aspx?tabid1979
23
Infiltration

• Not all precipitation enters the stream
• Must calculate effective precipitation
  (precipitation that is converted to runoff) using
  an infiltration model
• Many infiltration models have been developed
• One common model is the SCS Method (USDAs Soil
  Conservation Service, now Natural Resource
  Conservation Service NRCS)
• Assigns a curve number (CN) to many different
  land use categories
• CN range from 0 100 (completely pervious to
  completely impervious). Pavement is 98.

24
SCS Method

• Develops an empirical relationship between
  effective precipitation and actual precipitation

Ia initial abstraction (in) P the observed
precipitation (in) S maximum potential
retention (in) Q effective precipitation (in)
25
SCS Method

• The CN describes the maximum possible retention,
  where
• We assume Ia 0.2S, determined from a study of
  many small watersheds by SCS

26
SCS Curve Number
Source USDA NRCS TR-55
27
SCS Curve Number

• Adjustments are made for antecedent moisture
  conditions
• CN(II) is for average moisture conditions
• CN(I) and CN(III) are for dry and moist
  conditions, respectively

28
SCS Curve Number

• An analysis of rainfall-runoff relationships for
  Little Crum Creek has found a strong correlation
  between antecedent moisture and effective
  precipitation

29
SCS Curve Number
Source USDA NRCS TR-55
30
Problems with SCS

• Developed by USDA for use on agricultural land
  types
• Attempts to apply the SCS CN method to the Little
  Crum Creek watershed result in underestimates of
  the effective precipitation
• Not terribly useful for envisioning the effects
  of numerous parking lots, storm sewer drainage
  systems, etc.

31
Problems with SCS

• We calculated the theoretical CN(II) for one
  section of the watershed to be 88.8
• Underestimates total runoff
• Analysis of observed rain events shows that the
  actual CN is closer to 96
• Solutions (Easy and Hard)
• Account for roads (Easy)
• Find a new relationship between S and Ia (Hard)

32
Other Parameters

• Average impervious percentage, slope, conduit
  length, and elevations are determined from GIS
  analysis
• Elevations are from a Digital Elevation Map (DEM)
• Impervious percent is from a raster dataset that
  classifies land use into 5 categories

33
Land Use and Impervious Percent
34
Putting it all together

• Model currently built for a section of the
  watershed

Little Crum Creek Park
Girard
35
Close
36
Still close
37
Preliminary Results

• Simulated results either underestimate or
  overestimate the amount of flow
• This difference is sometimes quite pronounced,
  depending on the nature of the storm event
• Simulation results typically exhibit a time lag

38
Whats Next

• Adjust parameters to get a better fit to actual
  data
• Add capability to model Nitrate, Phosphate, and
  TSS to the model
• Model the implementation of BMPs and LID within
  the watershed

39
Low Impact Development
40
Modeling Low Impact Development and BMPs

• A completed model allows BMP and LID alternatives
  to be compared
• A benefit-cost analysis can be performed to
  determine the most economically efficient method
  of reducing runoff

41
Types of BMPs/LIDs

• Many ways to reduce runoff, including
• Green roof (we have one on the roof of Alice Paul
  and David Kemp)
• Constructed Wetland
• Cisterns and rain barrels
• Permeable pavement surfaces

42
Preliminary BMP Recommendations
Site BMP
Springfield Square, Springfield, PA Green Roof
Farmhouse Circle, Springfield, PA Constructed Wetland
See http//watershed.swarthmore.edu/littlecrum
for ongoing recommendations for all four
municipalities Springfield, Swarthmore, Ridley
Township, Ridley Park
43
Springfield Square
Green Roof on Swarthmores Alice Paul Hall
(image Meghan Whalen)
44
Farmhouse Circle
Constructed Wetland at Ridley High School
45
Questions?

• http//watershed.swarthmore.edu