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Hugo Neighborhood Association & Historical Society

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What Are Resource Lands?
Woodlot Resource To Non-Resource Lands
Evaluation: Internal Rate of Return - IRR
Top IRR Rated Agricultural Lands
Non-rated Soils & IRR System
Quasi-Judicial Plan Amendments
Compliance With Goal 3 -- Agricultural Lands
Compliance With Goal 4 - Forest Lands
Brown Report: IRR Zoning
Composite IRR

 

COMPOSITE IRR

Brochure 10 in IRR Series

 December 22, 2003

Land Use Committee
Hugo Neighborhood Association & Historical Society
Member of the CACNA Coalition

 __________

Policy 3, Goal 11 Josephine County Comprehensive Plan

Goal 11, Policy 3.B.(1) This Josephine County Comprehensive Plan (JCCP)1 policy permits requests involving changes for lands from a resource designation (i.e., woodlot resource) to a non-resource designation through the internal rate of return, or IRR procedure.2 The Hugo Neighborhood Association has concerns with the present application of the IRR system in the amendment process.3

 “A lot or parcel is considered forest land when the predominant (more than 50%) soil or soils on the parcel have an internal rate of return of 3.5 or higher (if a single forest-rated soil is present), or composite internal rate of return of 3.5 or higher (if multiple forest-rated soils are present).”

 Composite Internal Rate of Return (CIRR)

 How do you apply the CIRR method?

 1.  Identify the soils on the applicable parcel (i.e., map symbol and soil name)2 & 4 or conduct you own soils inventory.

2.  Develop a simple soils grid to determine the percent of each soil on the parcel.5

3.  Use Soils Rating For Josephine County (IRR) for each soil.2

3.  Summarize information in table (see example tables).

In the Table 1 example, IRR ratings include, 46 percent of the soils less than 3.5, 2 percent greater than 3.5, and 52 percent not rated.  You cannot calculate a CIRR without considering the forest productivity of all the soils.  A non-rated soil creates a need to utilized JCCP Policy 3.B.(2).

Example Table 1 - Site Soils Data

Map    Soil Name                                    IRR         %of
Symbol                                                                    Site
12D    Brockman Cobbly Clay Loam         0.00         52%
79F    Vannoy-Voorhies Complex              2.91         34%
21F    Comutt-Dubakella Complex            2.78         12%
42C    Holland Sandy Loam                       3.83         02%

What if a lot or parcel is composed of multiple forest rated soils and it is not obvious if the internal rate of return is 3.5 or less for the parcel. In this case a CIRR needs to be calculated (see example Table 2).  For this example soils 12D and 79F are assigned fictitious IRRs.  What is interesting about Table 2 is that 80 percent of the soils had an individual IRR greater than 3.5, but the composite IRR at 3.51 was barely above 3.5.

Example Table 2 - CIRR

Map    IRR                    %of        Comp
Symbol                           Site         Index
12D     2.00         X          11%  =     22.00
79F      3.76         X          39%  =  146.64
21F      2.78        X          09%  =     25.02
42C      3.83         X        41% =   157.03
                            Total         350.69
Composite IRR Index    3.51

More Information

What if we changed the percent of site slightly with less soils having an IRR above 3.5 (see Example Table 3).

Example Table 3 - CIRR

Map    IRR                    %of        Comp
Symbol                           Site         Index
12D     2.00         X          11%  =     22.00
79F      3.76         X          39%  =  146.64
21F      2.78        X          11%  =     30.58
42C      3.83         X        39% =   149.37
                            Total         338.59
Composite IRR Index    3.49

Table 3 demonstrates that 78 percent of the soils had an individual IRR greater than 3.5, but the composite IRR at 3.49 was just below 3.5.

More Information.  Would you like to learn more about citizen involvement in land use planning?  Contact a member of the Land Use Committee of the Hugo Neighborhood.

 Disclaimer.  This brochure is as much about providing information and provoking questions as it is about opinions concerning the adequacy of findings of fact and land use decisions.  It does not provide recommendations to citizens and it is not legal advice.  It does not take the place of a lawyer.  If citizens use information contained in this paper, its their personal responsibility to make sure that the facts and general information contained in it are applicable to their situation. (Link)

 1. Josephine County. October 2000. The Comprehensive Plan For Josephine County. Grants Pass, OR.

2. Lawrence F. Brown.  1985. Using The Internal Rate Of Return To Rate Forest Soils For Applications In Land Use Planning.  Grants Pass, OR.;  Michael Snider.  1999.  Locational Factors Affecting Woodlot Resource Lands.  Josephine County Planning Office.  Grants Pass, OR.

3. Hugo Neighborhood Association & Historical Society.  2003. The IRR Series:  Woodlot Resource To Non-Resource Lands; Evaluation: Internal Rate of Return - IRR; Top IRR Rated Agricultural Lands; Non-rated Soils Versus IRR System; Compliance With Goal 4 - Forest Lands, Brown Report: IRR Zoning, and  Amendments. Grants Pass, OR.

4. United States Department of Agriculture. Soil Conservation Service. December 1983. Soil Survey of Josephine County, Oregon. (Presently the Natural Resources Conservation Service).

5. David Summer’s land use application  before the Josephine County Rural Planning Commission August 25, 2003.

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2012 Hugo Neighborhood Association & Historical Society