Calculating Credits and Debits for Compensatory Mitigation in Wetlands of Western Washington. Patricia Johnson Washington State Department of Ecology

Transcription

1 Calculating Credits and Debits for Compensatory Mitigation in Wetlands of Western Washington Patricia Johnson Washington State Department of Ecology

2 Debits and Credits Debits = area-based units representing the loss of wetland functions at an impact site Credits = area-based units representing the gain of wetland functions at a mitigation site

3 Background Creates functional currency to compare functions and values lost to those proposed Based on the Washington State Wetland Rating System for Western Washington HGM based

4 Function Groups Improving water quality Water Quality Flood storage and flow reductions Hydrologic Habitat for plants and animals Habitat Photo courtesy of King County, WA

5 Score for each function based on a qualitative rating of: The potential of the site to provide the function The potential of the landscape to maintain each function at the site scale The values each function may have for society

6 What is the potential of the site to provide the function? Based on indicators of structure.

7 Site Potential:

8 What is the potential of the landscape to affect the function at the site scale?

9 Landscape Potential:

10 What is the value of the function to society?

11 Value:

12 Scoring for each function Site potential + Landscape potential + Value High = 3 Medium = 2 Low = 1 H,H,H = 9 H,H,M = 8 H,H,L = 7 H,M,M = 7 M,M,M = 6 H,M,L = 6 H,L,L = 5 M,M,L = 5 M,L,L = 4 L,L,L = 3

13 Example Wetland Impact (Debit): Before After

14 Example Wetland Impact (Debits) Rating of Wetland Unit BEFORE impact Function Improving Water Quality Hydrologic Habitat Site Potential (H, M, L) Landscape Potential (H, M, L) Value (H, M, L) M = 2 L L H = 3 H M L = 1 L L Score for Wetland Unit = 6 5 4

15 Losses (Debits) and Gains (Credits) are estimated by multiplying the score by the area and by the appropriate Modifier Photo courtesy of King County, WA

16 Calculating Debits Modifier: Temporal Loss Factor

17 Calculating Debits Score (Water Q.) x Area x TLF = Debits (Water Q.) Score (Hydrologic) x Area x TLF = Debits (Hydrologic) Score (Habitat) x Area x TLF = Debits (Habitat)

18 Example: DEBITS from Impact DELAYED Mitigation Improving Water Quality Hydrologic Habitat Score for Wetland Unit Acres of impact (non-forested) Basic mitigation requirement (BMR) 1 6 x 1 = Temporal loss factor (Delayed) 3 DEBITS 6 x 3 = Total Debits: = 45 Permittee purchases 45 credits from ILF Program

19 Calculating Credits Basic Credits = Increase in Score [Score at maturity of site Score before] Creation : Score before = 0 Re-establishment: Score before = 0 Rehabilitation: Score before = (from form) Enhancement: Score before = (from form)

20 Example ILF Mitigation Site (Credits) Before After

21 Example ILF Mitigation Site (Credits) Rating of Unit BEFORE mitigation Improving Water Quality Hydrologic Habitat Site Potential (H, M, L) Landscape Potential (H, M, L) Value (H, M, L) M = 2 M M H = 3 H L H = 3 H H Score = 8 8 6

22 Example ILF Mitigation Site (Credits) Rating of Unit AFTER mitigation Improving Water Quality Hydrologic Habitat Site Potential (H,M,L) Landscape Potential (H,M,L) Value (H,M,L) H = 3 H H H = 3 H L H = 3 H H Score = 9 9 7

23 Calculating Credits Modifier: Risk of Failure Type of Mitigation Advance mitigation The site meets criteria in Charts 1 and 3 of the site selection guidance [i.e. identified in a local plan and is sustainable] AND meets the criteria in Charts 4-11 for the appropriate functions. (Ecology publication # ) Advance means that at least two years has passed since plantings were completed or one year since as-built plans were submitted to regulatory agencies. Risk Factor Advance mitigation without meeting criteria in Ecology publication # Concurrent Mitigation Mitigation site meets criteria in Charts 1 and 3 of the site selection guidance [i.e. identified in a local plan and is sustainable] AND meets the criteria in Charts 4-11 for the appropriate functions. (All worksheets for Chart 3 and in Appendix D of Ecology publication # are submitted) Risk factor applies to all types of mitigation. Mitigation site chosen meets the criteria in Charts 2 and 3 of the site selection guidance [i.e. identified as a site with potential and that is sustainable] ; AND meets criteria in Charts 4-11 for the appropriate functions. (All worksheets for Chart 3 and in Appendix D of Ecology publication # are submitted) Risk factor applies to all types of mitigation. Site does not meet criteria in site selection guide, or guide was not used. Re-establishment, rehabilitation, or enhancement of an aquatic bed, shrub, or forest community Re-establishment, rehabilitation, or enhancement of an emergent community Creation of an aquatic bed, shrub, or forest community with data showing there is adequate water to maintain wetland conditions 5 years out of every 10. Creation of an emergent community with data showing there is adequate water to maintain wetland conditions 5 years out of every 10. Creation of an aquatic bed, shrub, or forest community without adequate hydrologic data. Creation of an emergent community without adequate hydrologic data

24 Calculating Credits Increase in Water Q. Score x Area x RF = Credits (Water Q.) Increase in Hydrologic Score x Area x RF = Credits (Hydrologic) Increase in Habitat Score x Area x RF = Credits (Habitat)

25 Example ILF Mitigation Site (Credits) Proposed Credits for CREATED Wetland Areas Rating of Unit AFTER mitigation Rating BEFORE mitigation Increase in Score (A-B) Improving Water Quality Hydrologic Habitat = Acres CREATED 1 Basic mitigation Credit 9 x 1 = Risk Factor 0.9 CREDITS 9 x 0.9 =

26 Example ILF Mitigation Site (Credits) Proposed Credits for Enhanced Wetland Areas Rating AFTER mitigation Rating BEFORE mitigation Increase in Score (A-B) Improving Water Quality Hydrologic Habitat = Acres ENHANCED 12 Basic mitigation Credit 1 x 12 = Risk Factor 0.9 CREDITS 12 x 0.9 =

27 Example ILF Mitigation Site (Credits) Proposed TOTAL Credits Improving Water Quality Hydrologic Habitat CREATED Credits ENHANCED Credits TOTAL CREDITS = Total Credits: = 54.9 PROPOSED Total Credits for the Project = 54.9

28 Comparing Debits to Credits Wetland Impact Debits with Delayed TLF: 45 total Debits 18 debits for Water Quality 15 debits for Hydrologic 12 debits for Habitat PROPOSED Credits for ILF Mitigation Site: 54.9 total Credits 18.9 credits for Water Quality 18.9 credits for Hydrologic 17.1 credits for Habitat

29 An ILF mitigation site must fulfill at least as many credits (released) as the number sold to permittees (debits). Photo courtesy of King County, WA

30 Credit Debit Tool is Guidance SCORES from the Tool provide a STARTING POINT Tool may not capture site-specific factors on debit or credit end Do not want Tool to drive the design

31 Questions? Patricia Johnson WA Dept. of Ecology (360)