US Army Corps of Engineers
Albuquerque District Website

SPECIAL PUBLIC NOTICE: Colorado Stream Quantification Tool v1 Approved for Use

Published Sept. 29, 2020

PURPOSE: The U.S. Army Corps of Engineers, Albuquerque (SPA), Omaha (NWO), and Sacramento (SPK) Districts, (Corps) hereby approves the statewide use of the Colorado Stream Quantification Tool (CSQT) v1.0. The CSQT provides a common currency for calculating lift (credits) and loss (debits) associated with stream mitigation sites and permitted activities that may require compensatory mitigation. This public notice provides a summary of the changes that were made to the CSQT based on the results of beta-testing and in response to public notice comments.


LOCATION: The CSQT applies within the Regulatory boundaries of the Albuquerque, Omaha, and Sacramento Districts in the State of Colorado.

BACKGROUND: Compensatory Mitigation for Losses of Aquatic Resources (33 CFR 332), also known as the Final Rule, establishes standards and criteria for the use of compensatory mitigation to offset unavoidable impacts to waters of the United States (WOTUS). The Final Rule directs the Corps, when determining the amount of compensatory mitigation required to offset losses associated with unavoidable impacts to aquatic resources, to ensure the compensation is “sufficient to replace lost aquatic resource functions.” Furthermore, “… where appropriate functional or condition assessment methods or other suitable metrics are available, these methods should be used where practicable to determine how much compensatory mitigation is required.”
Following publication of the Final Rule, the Corps assessed its ability to meet the requirements of the Final Rule in Colorado and, in 2013, determined its approach to stream mitigation did not meet the requirements of the Final Rule in Colorado.

On March 24, 2017, in collaboration with the Environmental Protection Agency (EPA), the Corps completed a review of existing stream mitigation procedures and available functional and condition assessment methods (FCAMs). Based on the findings of this collaborative review, the Corps selected regionalization of SQT and development of stream mitigation procedures as the preferred approach to meet the requirements of the Final Rule in Colorado.

In May of 2019, the Albuquerque and Omaha Districts completed development of the CSQT trial (beta) version and Colorado Mitigation Procedures (COMP) v1.0. On May 10, 2019, issued public notices (PNs) approving the use of the CSQT beta and COMP v1.0 on all lands in Colorado east of the Continental Divide. On August 22, 2019, the Albuquerque and Omaha Districts extended the public comment period until October 11, 2019.
On September 19, 2019, the Sacramento District issued a PN initiating a 30-day comment period on the use of the CSQT beta and COMP v1.0 on lands in Colorado west of the Continental Divide. On October 15, 2019, Sacramento District extended the public comment period until November 19, 2019.

Between July 11 and September 26, 2019, the Corps hosted four Regulatory Workshop to provide the public with information about the COMP and CSQT and the effects of their implementation on 404 permit requirements in Colorado.

From November 2019 until May 2020, the Corps collaborated with the CSQT interagency Steering Committee to complete a review of all CSQT beta documents and evaluate comments received during the public notice comment period (May 10, 2019 – November 19, 2019).

On June 26, 2020, the Corps completed revisions to the COMP and issued a public notice approving the use of COMP v2.0.

SUMMARY OF CHANGES TO CSQT: The Corps received a wide range of comments and made changes to the CSQT, where applicable, in the follow areas:

1. Alternative Tools – the Corps acknowledges that there are other FCAMs that may provide utility to the Corps Regulatory Program. However, the purpose of the CSQT is to provide a “common currency” to aid the Corps in calculating stream mitigation debits and credits. As stated above, the Corps evaluated available FCAMs and determined the CSQT best met the Corps needs;

2. Applicability and Use – the Corps made substantive changes to the CSQT User Manual and Science Support Document to clarify the applicability and intended use of the CSQT in various stream types and settings;

3. Complexity & Potential for Misapplication – the Corps acknowledges the potential for misapplication due to the complexity of stream systems. The Corps made efforts to minimize these concerns by updating the User Manual to clarify applicability of the parameters and metrics and explain where less comprehensive approaches may be appropriate to meet the needs of different permit scenarios (i.e., basic suite). As always, the Corps encourages pre-application consultation to provide applicants and the Corps with the opportunity to determine the best approach to avoidance, minimization, and compensatory mitigation for unavoidable impacts to WOTUS;

4. Data Collection Methods – the CSQT utilizes existing data collection methods commonly used on stream projects and does not create any new data collection methods. The Corps has made improvements to the User Manual and Science Support Document to clarify data collection requirements and better explain the tiered-capability of the CSQT;

5. Debit Calculator – the Corps corrected calculation errors in the Debit Calculator and removed bottomless arch culverts from the list of examples under Tiers 3 and 4 (bottomless arch culverts are now listed as an example only under Tier 2);

6. Editorial, Definitions, References, & Acronyms – the Corps completed editorial changes throughout the CSQT documents to improve readability;

7. Expertise & Training Requirements – the Corps acknowledges that training and field experience is necessary to ensure proper data collection and appropriate use of the CSQT. The metrics used in the CSQT are derived from existing FCAMs commonly used on stream projects, so practitioners with experience working on stream projects, especially qualified stream restoration specialists, should be familiar with the CSQT parameters, metrics, and data collection methods, such that a significant amount of additional training costs/requirements and field experience should not be necessary in order to use the CSQT;

8. Flow Alteration Module – the Corps made improvements to the Flow Alteration Module in the CSQT, clarified the recommended use of this module in the User Manual, and provided supporting rationale in the Science Support Document;

9. Forms – the Corps made various changes to the layout and content of forms to improve efficiency, repeatability, and functionality;

10. Metrics – the Corps acknowledges the numerous comments pertaining to the addition, removal, modification, or relocation of metrics (from one parameter to another). The Corps made changes, where appropriate, to ensure parameter calculations accurately account for changes in stream conditions for the purpose of calculating mitigation debits/credits. The Corps has revised the Science Support Documentation to include rationale for all metrics included in the CSQT;

11. Monitoring Requirements – the Corps acknowledges the importance of monitoring and the value of accurate, meaningful data in order to document and ensure project success. However, monitoring requirements are determined case-by-case in accordance with COMP v2.0;

12. Opposition to the CSQT – the Corps acknowledges recommendations to terminate or disapprove the use of the CSQT. The Corps determined the CSQT is the preferred alternative that will best meet the Corps’ needs in complying with 33 CFR 332;

13. Parameters – the Corps acknowledges comments pertaining to the CSQT parameters and made changes, where appropriate, to ensure calculations accurately capture the changes in stream conditions, as intended;

14. Reference Reaches – the Corps made changes to clarify the criteria for selecting appropriate reference reaches;

15. Regional Curves – the Corps acknowledges the importance of selecting appropriate regional curves. The flexibility to develop new curves, where necessary, addresses these concerns;

16. Results from Beta Testing – the Corps made improvements to the CSQT based on the results of beta testing;

17. Science Support – the Corps made improvements to the Science Support Document to increase the level of documentation and rationale for the parameters/metrics included in the CSQT. The Corps also made changes to the User Manual clarifying that the CSQT is not solely form-based but, rather, includes elements of both process and form based approaches;

18. Scoring and Weighting – the Corps completed additional testing and adjusted scoring and weighting, where necessary, to address concerns with the accuracy, consistency, manipulability, and repeatability of the CSQT;

19. Stream Length vs. Valley Length vs. Floodplain Area – the Corps acknowledges there are multiple approaches to calculating stream functions and conditions currently being applied across the Nation. As stated above, the Corps evaluated various approaches and determined stream length is an acceptable basis for measuring stream conditions. Furthermore, approval and use of the CSQT does not preclude the consideration of other values, such as area of impact, in determining mitigation requirements in association with 404 permits. These considerations are addressed by COMP v2.0, South Pacific Division (SPD) Mitigation Ratio-Setting Checklist, and SPD Mitigation and Monitoring Guidelines;

20. Testing and Delayed Implementation – the Corps acknowledges recommendations for further testing and determined the testing completed during the public notice comment period, which is documented in the Science Support Document, is adequate to approve the use of CSQT v1. The Corps acknowledges the value in testing and will continue to test and evaluate the results of CSQT v1 assessments to verify accuracy and identify potential improvements for future versions;

21. Time & Resource Commitments – the Corps acknowledges CSQT assessments requires time and resources, but these additional time and resource commitments are reasonable and appropriate where function-based compensatory mitigation may be required to ensure regulatory compliance (i.e., 33 CFR 332.3). Furthermore, as stated above, the Corps maintains the discretion to determine when the CSQT or other applicable FCAMs may be required.

AVAILABILITY: CSQT v1.0 is available on our webpage at All CSQT files, including archived beta documents, are also available to the public on the RIBITS website under Colorado Assessment Tools and Stream Mechanics website.

POINTS OF CONTACT: For additional information, please contact one of the following Corps representatives:

Albuquerque District  Omaha District  Sacramento District
Joshua Carpenter  Aaron Eilers  Travis Morse
(719) 543-9459 X 2  (720) 922-3851  (970) 243-1199 X 1014