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- Question 1: Is
Region 5 Model only for EPA Region 5 states?
- Question 2: What
are the differences between STEPL and Region 5 Model?
- Question 3: My
‘Total Load’ worksheet has ‘#VALUE!’ in result cells. What went wrong?
- Question 4: The
septic system failure rate seems low, are there other alternative data?
- Question 5: How
can I add my own BMPs to STEPL’s BMP list?
- Question 6: Where
can I find the definitions of BMPs used in the STEPL and Region 5 Model?
- Question 7: Can
you help me use the BMP Calculator?
- Question 8: What
are other models that can be used for load reduction calculations?
- Question 9: If
I don't know exactly where all my BMPs for a particular subwatershed are
located (not knowing if they're in the same fields or even affecting the
same tributary) am I better off calculating them in serial or in parallel
configuration for that subwatershed?
- Question 10: Why
is the STEPL-calculated sediment loading rate (t/ac/yr) from my watershed
much lower than the erosion rate (> 1 t/ac/yr) reported for my study
area? Can you explain?
- Question 11: Some
of the data I'm gathering to input into the STEPL model is not
consistent. For filter strips,
I have some data coming to me as actual acres of filter strip, and some
coming to me as acres affected by the filter strip. What is the best way to deal with
these discrepancies in the model?
- Question 12: My
general question is whether it is appropriate to use STEPL to compare the loading
effects of changing a particular site from one land use to another, e.g.,
agricultural to commercial. I
also wonder how it applies the USLE to "soil loss" from a parking
lot.
***************************
·
Question 1: Is Region 5 Model only for EPA Region 5 states?
No, Region 5 Model can be used for other states. The model got its
name because it was originally developed in Indiana Department of
Environmental Management based on Michigan Department of Environmental Quality’s
319 watershed training manual. Both Indiana and Michigan are EPA Region 5
states.
·
Question 2: What are the differences between STEPL and Region 5 Model?
Below are the major differences between the two models:
Region 5 Model
- Calculates load at the source level
- Sources are independent (no relationship
between worksheets)
- Users can not specify and update BMPs used
in the model
- Has gully erosion and streambank erosion
calculations
STEPL
- Calculates load for different sources at
source and watershed level
- Sources are related in watershed
- Users can specify and update BMP list
- Users can use BMP calculator to estimate
combined BMP efficiencies for complex BMP arrangements
- On-line input data server for initial model
setup (Caution: Do not substitute the on-line data for real local data!!!)
- No gully erosion and streambank erosion
calculations.
·
Question 3: My ‘Total Load’ worksheet has ‘#VALUE!’ in result cells. What
went wrong?
You probably entered some non-numerical characters in the input tables on
the ‘Input’ sheet. For example, when you copy and paste ‘Agricultural
animals’ data from the tables generated by the ‘STEPL Input Data Server’,
you may paste non-numerical characters to the STEPL input sheet if the
animal number is indicated with ‘D’ for data withheld to avoid disclosing
by US Department of Agriculture.
·
Question 4: The septic system failure rate seems low, are there other
alternative data?
Yes. The failure rate data have very high
uncertainty. Users are encouraged to obtain the septic failure rate from
their local health departments.
Besides the data from the ‘STEPL Input Data Server’ (National
Environmental Service Center formally National Small Flow Clearinghouse, 1992
and 1998), Electric Power Research Institute conducted a state-by-state
survey on septic failure rate. Below is the summary:
|
State
|
Estimated
system failure rate (in %)
|
Failure
definition
|
|
Alabama
|
20
|
Not
given
|
|
Arizona
|
0.5
|
Surfacing,
backup, surface or ground water contamination
|
|
California
|
1-4
|
Surfacing,
backup, surface or ground water contamination
|
|
Florida
|
1-2
|
Surfacing,
backup, surface or ground water contamination
|
|
Georgia
|
1.7
|
Public
hazard
|
|
Hawaii
|
15-35
|
Improper
construction, overflow
|
|
Idaho
|
20
|
Backup,
surface or ground water contamination
|
|
Kansas
|
10-15
|
Surfacing,
nuisance conditions (for installations after 1980)
|
|
Louisiana
|
50
|
Not
given
|
|
Maryland
|
1
|
Surfacing,
backup, surface or ground water contamination
|
|
Massachusetts
|
25
|
Public
health
|
|
Minnesota
|
50-70
|
Cesspool,
surfacing, inadequate soil layer, leaking
|
|
Missouri
|
30-50
|
Backup,
surface or ground water contamination
|
|
Nebraska
|
40
|
Nonconforming
system, water quality
|
|
New
Hampshire
|
<5
|
Surfacing,
backup
|
|
New
Mexico
|
20
|
Surfacing
|
|
New
York
|
4
|
Backup,
surface or ground water contamination
|
|
North
Carolina
|
15-20
|
Not
given
|
|
North
Dakota
|
28
|
Backup,
surfacing
|
|
Ohio
|
25-30
|
Backup,
surfacing
|
|
Oklahoma
|
5-10
|
Backup,
surfacing, discharge off property
|
|
Rhode
Island
|
25
|
Not
given
|
|
South
Carolina
|
6-7
|
Not
given
|
|
Texas
|
10-15
|
Surfacing,
surface or ground water contamination
|
|
Utah
|
0.5
|
Surfacing,
backup, exceeding discharge standards
|
|
Washington
|
33
|
Public
health hazard
|
|
West
Virginia
|
60
|
Backup,
surface or ground water contamination
|
|
Wyoming
|
0.4
|
Backup,
surfacing, ground water contamination
|
·
Question 5: How can I add my own BMPs to STEPL’s BMP list?
You can add, delete, or edit BMPs in the “BMPList” worksheet, which can be
shown (unhidden) by clicking the STEPL > View/Edit BMP List menu. On
‘BMPlist’ worksheet, follow the steps outlined on the top-right corner. See
more information in section 4.6 of the STEPL user’s guide.
·
Question 6: Where can I find the definitions of BMPs used in the STEPL and
Region 5 Model?
You can find BMP descriptions in a Microsoft Word document,
BMPDefinition.doc, under your [Local Drive C or D]:\STEPL folder after you
install STEPL on your PC.
·
Question 7: Can you help me use the BMP Calculator?
Yes. The STEPL user’s guide has a detailed section (Appendix A) that
describes the procedures and examples of using the BMP Calculator.
·
Question 8: What are other models that can be used for load reduction
calculations?
STEPL and Region 5 models are two of the simplest models for calculating
pollutant load reductions. There are many other models that can be used to
calculate the load reductions, and these models are described in a document
in the STEPL Web site. You can download the document by clicking on ‘List
of Alternative Load and Load Reduction Model’ from: http://it.tetratech-ffx.com/stepl/models$docs.htm.
·
Question 9:
If I don't know exactly where all my BMPs for a particular
subwatershed are located (not knowing if they're in the same fields or even
affecting the same tributary) am I better off calculating them in serial or
in parallel configuration for that subwatershed?
Most non-structural BMPs should be used in parallel configuration (with the
BMP Calculator) if you do not know their locations and spatial
relationship. Some downstream structural BMPs or on stream BMPs may be in
serial connection with the upstream BMPs. e.g., a sediment settling pond
may be in serial to upstream BMPs such as no-till practices. If you do not
know the BMP locations in a watershed, assuming parallel BMP configurations
will be better than assuming serial configurations if most of the BMPs are
non-structural (except filter strips) or not in-stream.
·
Question 10: Why is the STEPL-calculated sediment loading rate
(t/ac/yr) from my watershed much lower than the erosion rate (> 1 t/ac/yr)
reported for my study area? Can you explain?
The sediment output from a watershed is different from on-site erosion. For
cropland in your calculation, erosion rate may be larger than 1 t/ac/yr;
however, the sediment output from your watershed is much lower. The STEPL
model calculates sediment output using "erosion x sediment delivery
ratio". Your watershed area is pretty large, so it results a low
sediment delivery ratio. To see the sediment delivery ratio in STEPL model,
click on STEPL menu > unhide/hide other STEPL sheets, and navigate to
the ‘Sediment’ worksheet, and then check cell "W9". Your can
modify the sediment delivery ratio based on your local data.
·
Question 11:
Some of the data I'm gathering to input into the STEPL model is not
consistent. For filter strips,
I have some data coming to me as actual acres of filter strip, and some
coming to me as acres affected by the filter strip. What is the best way to deal with
these discrepancies in the model?
The important data that STEPL needs is the acreage affected by a filter
strip. For example, if you have 20 acres of cropland affected by a filter
strip, you can choose "Cropland-filter strip" as the BMP in STEPL
and apply it to the affected area for load reduction calculation. The
actual area of a filter strip is less important than the area it controls
due to the factor that (1) the area of the filter strip is usually
significant smaller than the affected area, and (2) the filter strip is not
a source of non-point source pollution (in STEPL, you may exclude it from
the load calculation or treat it as a type of forest).
·
Question 12:
My general question is whether it is appropriate to use STEPL to compare
the loading effects of changing a particular site from one land use to
another, e.g., agricultural to commercial. I also wonder how it applies the USLE to "soil loss"
from a parking lot.
For assessment and planning purposes, you can use STEPL to compare effects
of land use changes on pollutant loads (N, P, and sediment). However, STEPL
was created to only give rough estimates on load and load reduction, and it
is not intend for making very precise predictions. For urban land uses,
STEPL does not use USLE. STEPL uses annual runoff volume x pollutant
concentration to estimate pollutant loads, including sediment load.
More Questions? Please contact:
STEPL
support
Developed for EPA Office of Water
Grants Reporting and Tracking System
By Tetra Tech, Inc.
Last revised: 09/07/2005
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