TO WHOM IT MAY CONCERN: The U.S. Army Corps of Engineers (USACE), Rock Island District, has combined the Illinois Stream Mitigation Method and the Iowa Stream Mitigation Method to create the Rock Island Stream Mitigation Method (RISMM). The RISMM establishes a standardized approach for determining the amount of stream mitigation credits required to offset unavoidable impacts and the amount of stream mitigation credits generated through mitigation activities within the Rock Island District, which encompasses Iowa and Illinois. The RISMM has been revised to update outdated information and incorporate new regulatory guidance. The updated method provides applicants with information to help estimate potential compensatory mitigation requirements for unavoidable stream impacts and to assist in initiating the development of new mitigation projects within the Rock Island District. The RISMM will be used in the evaluation of activities authorized pursuant to Section 404 of the Clean Water Act (33 U.S.C. § 1344) and Section 10 of the Rivers and Harbors Act (33 U.S.C. § 403).
APPLICANT: U.S. Army Corps of Engineers, Rock Island District
SIGNIFICANT CHANGES:
1. Changed stream terminology from ephemeral, intermittent, & perennial to nonrelatively permanent water (non-RPW) & relatively permanent water (RPW). Furthermore, non-RPW (formerly ephemeral) has been excluded from the Adverse Impact Factor section, and the In-Stream Benefit Factor for non-RPWs has been adjusted from 0.15 to 0.1.
2. The Restored Reach category has been removed, and the list of Priority Water criteria for both Illinois and Iowa has been consolidated under the categories of Primary and Secondary waters.
3. Language in both the Fully Functional and Functionally Compromised categories of the Existing Conditions section have been revised for greater specificity and clarity.
4. Eliminated “Armored Revetments,” “Below Grade Culvert,” and “Detention Facility” sections from Impact Activity. Additionally, the Impact factor for “Morphologic Change” was decreased from 1.5 to 1.0.
5. Eliminated “Tertiary” from Service Area classification.
6. Eliminated the “Project Accommodation” category from In-Stream Net Benefits and split the “Excellent” category into “Excellent Small Watershed, 1st & 2nd Order RPW” and “Excellent Large Watershed, 3rd & above Order RPW.” Additionally, added Low-Tech Process-Based Restoration in the "Good" Category
7. Increased the required ratio credits generated from in-stream work from 25% to 33%.
8. Revised the “Temporal Lag” section for clarity and added a new factor “Forested Enhancement.”
GUIDANCE LOCATION: The updated Rock Island Stream Mitigation Method draft can be found at the following location: https://usace.contentdm.oclc.org/utils/getfile/collection/p16021coll9/id/3224
COMMENTS: USACE is soliciting comments from the public, federal, state, and local agencies, and officials, Indian Tribes, and any other interested parties. Comments should be submitted on or before the expiration date specified at the top of the page. A redline comparison report can be provided upon request, using the Iowa Stream Method as the baseline comparison document.
REPLY TO THE CORPS OF ENGINEERS: Comments or questions concerning this notice may be sent via email to iowaregulatory@usace.army.mil or illinoismoregulatory@usace.army.mil, or by calling 309-386-3173, or by writing to the following address:
US Army Corps of Engineers, Rock Island District
ATTN: Regulatory Department
Clock Tower Building
Post Office Box 2004
Rock Island, Illinois 61204-2004