DRAFT MEMORANDUM

TO:	  SEQ CHAPTER \h \r 1 Public Record for the Effluent Limitations
Guidelines and Standards for the Construction and Development Industry

FROM:	Tetra Tech, Inc.

 

DATE:	11 November 2008

SUBJECT:	Electronic File Documentation

Overview

The purpose of this memorandum is to document electronic files used in
modeling effects of effluent limitations guidelines (ELG) for the
Construction and Development (C&D) industry.  The archived files are in
spatial (vector and raster/grid), spreadsheet (Excel file), and database
(MS Access) formats.  Table 1 documents spatial data used in the
analysis, and Table 2 presents a list of data summaries in an MS Access
database. More extensive descriptions of the electronic data structures
and their roles in the analysis follow the tables.

Table   SEQ Table \* ARABIC  1 . Summary of spatial data files

Data Type	Spatial Data Files in Archive

Background

	States vector file	Urban Areas vector file

Erosivity

	R Factor grid

Land Cover Change

	USGS ERF1 -- Enhanced River Reach File 1.2 vector file

	Area NLCD 1992-2001 Land-cover Change Estimates by ERF1.2 (dbf file)
Percent NLCD 1992-2001 Land-cover Change Estimates by ERF1.2 (dbf file)

Precipitation

	PRISM United States Average Monthly or Annual Precipitation, 1971 –
2000 grid

Soils/Soil Fractions	USDA State Soil Geographic Database (STATSGO)
Mapping Units vector file

	

Table 2. List of database tables summarizing data derived from analyses

Table	Description

Annual urban ppt inches	Urban area average annual precipitation

Dev_ppt	ERF1.2 30 year average annual precipitation (inches and change
in developed acreage (1992-2001)

Erf12_area	Area (sq m) of ERF1.2 watershed NLCD change 1992-2001

Erf12_pct	Percent of ERF1.2 watershed NLCD change 1992-2001

Hyd Group by State	State HYD group from STATSGO

Kfactor	ERF1.2 K Factor from STATSGO

PPT_monthly_percent_State	PRISM monthly precipitation averages by state

Rvalue	ERF1.2 R value

Slopes	ERF1.2 Slope from STATSGO

St_rf1_USA	State and ERF1.2 intersections with area

Wted_Soil_Fraction_RF1ST	STATSGO soil fractions per state/ERF1.2 polygon



Data Descriptions

Spatial files

The following spatial files are intended to provide general background
layers for mapping the subsequent spatial data sets.

States

The States.shp was taken from the 2002 Environmental Systems Research
Institute, Inc. (ESRI) data disk ESRI Data & Maps 2002 (CD 3).  The
basic file is used for representing the fifty states and the District of
Columbia of the United States at a 1:100,000 scale.

Urban Areas

The UrbanAreas.shp was taken from the U.S. National Atlas Urbanized
Areas file from ESRI data disk ESRI Data & Maps 2002 (CD 2).  At a
1:1,500,000 scale, the U.S. National Atlas Urbanized Areas file
represents urban areas in the United States derived from the urban areas
layer of the Digital Chart of the World.

Erosivity (R Factor)

Erosivity describes the potential for soil to wash off disturbed,
denuded earth into waterways during storms.  Using a computer model
supported by soil and rainfall data, U.S. Department of Agriculture
(USDA) established estimates of annual erosivity values (R) for sites
throughout the country. These R factors are used as surrogate measures
of the impact that rainfall has on erosion from a particular site. The
1-kilometer raster grid ArcInfo grid rmap was derived in 2008 from the
LEW tool on the Tetra Tech NPDES website.

Land Cover Change (ERF1 -- Enhanced River Reach File 1.2)

The Enhanced River Reach File 1.2 (ERF1.2) Watersheds were released by
USGS in November 2003.  The digital segmented network based on watershed
boundaries, ERF1.2, includes enhancements to the U.S. Environmental
Protection Agency's River Reach File 1 (RF1) (USEPA 1996; DeWald and
others 1985) to support national and regional-scale surface
water-quality modeling.  ERF1.2 serves as the foundation for SPARROW
(Spatially Referenced Regressions (of nutrient transport) on Watershed)
modeling.  This version of the network expands on ERF1 (Version 1.2;
Alexander et al. 1999) and includes the incremental and total drainage
area derived from 1-kilometer (km) elevation data for North America.  A
1-kilometer raster grid of ERF1.2 was merged with the HYDRO1K flow
direction data set to generate a DEM-based watershed grid.  This grid
was used to summarize land use change and analyze development rates
across the country for the Construction and Development Effluent
Limitation Guideline.  

Area NLCD 1992-2001 Land-cover Change Estimates by ERF1.2

Percent NLCD 1992-2001 Land-cover Change Estimates by ERF1.2

Wickham and Wade (EPA/ORD/NERL/ESD/LEB) processed area and percent of
urban land cover change in February 2008 to create NLCD 1992-2001
Percent Land-cover Change Estimates by ERF1.2.  The land cover change
estimates were derived from the NLCD 1992/2001 Retrofit Land Cover
Change Product on an ERF1.2 level for the contiguous United States. 
Percent of land cover changing between the two time periods (1992 and
2001) in an ERF watershed is presented and can be joined to a spatial
file (ERF12_Watershed GRID_CODE).  The ERF1.2 watershed summarization of
developed land cover change provides a basis for estimation of national
development rates for the C&D ELG.

Precipitation (United States Average Monthly or Annual Precipitation,
1971 – 2000)

The PRISM Group at Oregon State University created the precipitation
data set that contains spatially gridded average monthly and annual
precipitation for the climatological period 1971-2000. Distribution of
the point measurements to a spatial grid was accomplished using the
PRISM (Parameter-elevation Regressions on Independent Slopes Model)
model, developed and applied by Chris Daly of OSU PRISM Group.  PRISM is
an analytical model that uses point data and an underlying grid such as
a digital elevation model (DEM) or a 30 yr climatological average (e.g.
1971- 2000 average) to generate gridded estimates of monthly and annual
precipitation and temperature (as well as other climatic parameters).
Grids were modeled on a monthly basis and annual grids of temperature
were produced by averaging the monthly grids, and summing for
precipitation.

Soils (USDA State Soil Geographic Database (STATSGO) Mapping Units)

This dataset contains files specifying the 10,500 map units defined for
the 48 conterminous states for the STATSGO soils data compiled by the
Natural Resources Conservation Service (NRCS) of the USDA.  This
database was created by generalizing soil-survey maps, including
published and unpublished detailed soil surveys, county general soil
maps, state general soil maps, state major land resource area maps, and,
where no soil survey information was available, Landsat imagery. 
Because climate and hydrology models require information about soil
physical properties in the form of continuous distributions rather than
discrete classes, soil fractions were derived for the 11 standard layers
for each map unit using the STATSGO Component and Layer tables.  In the
case of soil texture, the relative proportions of sand, silt, and clay
provide an alternative to discrete texture classes

Database files

The MS Access database (DEVT_Summary_DB.mdb) contains tables summarizing
results of major data processing efforts.

Development data are presented in Dev_ppt, Erf12_area, and Erf12_pct
tables.  Precipitation data are included in Annual_urban_ppt_inches,
Dev_ppt, and PPT_monthly_percent_State.  Hyd Group by State, Kfactor,
Rvalue, Slopes, and Wted_Soil_Fraction_RF1ST summarize data for states
or watersheds derived from STATSGO.  St_rf1_USA refers to a boundary
intersection of states and ERF1.2 watersheds and is used for scaling
watershed level data up to the state level, or vice versa.

Annual urban ppt inches

Annual precipitation (inches) averages derived from the PRISM Group at
Oregon State University data are provided for 6054 urban areas in the
contiguous United States.

Dev_ppt

ERF1.2 watershed estimates of area in square meters and acres in 2001
and 1992 in urban land cover are presented in this table.  Average
annual precipitation (inches) is also given for each watershed.

Erf12_area and Erf12_pct

These tables provide the raw output of the Wickham and Wade
(EPA/ORD/NERL/ESD/LEB) February 2008 analysis showing area and percent
of urban land cover change between 1992 and 2001 NLCD.  Included are
areas for land cover categories of forest, wetland, shrub, agriculture,
barren, and water.

Hyd Group by State

For each state in the contiguous United States, this table presents the
amount of land that falls into the hydrologic groups A, B, C, D, and W
(water).  Hydrology Class A soils have high infiltration rates.
Hydrology Class B soils have moderate infiltration rates. Hydrology
Class C soils have slow infiltration rates. Hydrology Class D soils have
very slow infiltration rates.

K-factor

The K factor was summarized for every ERF1.2 watershed based on STATSGO
K fact and K ffact parameters. The K factor is the soil erodibility
factor that represents both susceptibility of soil to erosion and the
rate of runoff.

PPT_monthly_percent_State

This table shows percent of annual precipitation for each month of the
year, derived from on 1971–2000 averages from the PRISM Group at
Oregon State University data.  State estimates were based on the monthly
precipitation proportions in each state’s urban areas. 

R-value

The minimum, maximum, and average R values for the rainfall-runoff
erosivity factor from STATSGO is provided for each ERF1.2 watershed.

Slopes

Minimum and maximum slope values from STATSGO are provided for each
ERF1.2 watershed.

St_rf1_USA

This table provides areas of watersheds that span state boundaries and
can be used to scale data from a watershed basis to a state estimate.

Wted_Soil_Fraction_RF1ST

Percent silt, percent sand, and percent clay values derived from STATSGO
are provided for each ERF1.2 watershed.

Other files

Clay_fraction_StateEst.xls was a preliminary file meant for exploration
of percent acreages per state and watershed that fell within given
percent clay ranges.  The weighted soil fraction table results in the MS
Access database now present this data in another form.

Top10URBAN.xls reflects the methods used for selection of indicator city
per EPA region.  Percent urban change and amount of urban acreage change
were calculated for urban areas in each region and then ranked to
support selection of indicator cities.

STATSGO_Tables.mdb is a MS Access database of original STATSGO data
tables that were used to derive results using the ERF1.2 watershed,
urban area, and state boundary files.

