Skip to Content


Causal Analysis of Biological Impairment in Long Creek: A Sandy-Bottomed Stream in Coastal Southern Maine

Document Details

Information about this document as published in the Federal Register.

Published Document

This document has been published in the Federal Register. Use the PDF linked in the document sidebar for the official electronic format.

Start Preamble


Environmental Protection Agency (EPA).


Notice of availability.


EPA is announcing the availability of a final report entitled, “Causal Analysis of Biological Impairment in Long Creek: A Sandy-Bottomed Stream in Coastal Southern Maine” (EPA/600/R-06/065F), which was prepared by the National Center for Environmental Assessment (NCEA) within EPA's Office of Research and Development (ORD).


The document is available electronically through the NCEA Web site at:​ncea. A limited number of paper copies will be available from the EPA's National Service Center for Environmental Publications (NSCEP), P.O. Box 42419, Cincinnati, OH 45242; telephone: 1-800-490-9198; facsimile: 301-604-3408; e-mail: Please provide your name, your mailing address, the title, and the EPA number of the requested publication.

Start Further Info


Information Management Team, National Center for Environmental Assessment (8623P), U.S. Environmental Protection Agency, 1200 Pennsylvania Avenue, NW., Washington, DC 20460; Telephone: 703-347-8561; e-mail:

End Further Info End Preamble Start Supplemental Information


This assessment presents results from a complex causal assessment of a biologically impaired, urbanized coastal watershed—the Long Creek watershed. The primary goals of this case study include the following.Start Printed Page 16009

First, the assessment serves as an example EPA Stressor Identification (SI) case study, whereby the report may help future assessors understand the SI process for other biologically impaired ecosystems and the scientific community better understand urban-related stressor interactions. Target audience members may include government agency and consulting firm scientists attempting to conduct their own case studies and managers interested in learning what the SI process is capable of.

Second, the assessment provides useful information for the specific environmental improvement of the Long Creek watershed. This is especially timely, as managers are currently considering options for promoting ecological recovery of the watershed.

The Long Creek watershed is biologically impaired and located primarily in South Portland, Maine. A relatively unimpaired upstream portion of the Red Brook watershed, adjacent to and immediately south of Long Creek, provides a reference condition and is also discussed in the report. The contributing watersheds of both streams are urbanized, home to industrial, commercial, and residential land uses. The Long Creek and Red Brook watersheds showcase a wide range of topics related to resource management including the environmental implications of urban land use for coastal regions and the interactions among multiple causes linked to biological impairment.

The Long Creek project team, consisting of the U.S. EPA and Maine Department of Environmental Protection, followed U.S. EPA's SI guidance to conduct the case study. A rudimentary knowledge of the SI process may assist report readers; U.S. EPA's CADDIS (Causal Analysis/Diagnosis Decision Information System) Web site,​caddis/​, provides causal assessors with the most recent SI methodology.

The project team identified four specific biological effects defining impairment and seven candidate causes of impairment. The biological effects include decreased Ephemeroptera, Plecoptera, and Trichoptera (EPT) generic richness, increased percentage of non-insect taxa individuals, increased Hilsenhoff Biotic Index (HBI) score, and absence of brook trout. Candidate causes include increased onsite organic production (or autochthony), decreased dissolved oxygen, altered flow regime (increased hydrologic flashiness, including decreased baseflow and increased peaks), decreased large woody debris, increased sediment, increased temperature, and toxic substances (including, e.g., metals and ionic strength).

Specific biological effects and candidate causes were evaluated at three impaired sites on Long Creek. Implications associated with interactions among probable causes of impairment are discussed in terms of this case study and causal assessment in general.

Start Signature

Dated: March 14, 2008.

Rebecca Clark,

Acting Director, National Center for Environmental Assessment.

End Signature End Supplemental Information

[FR Doc. E8-6166 Filed 3-25-08; 8:45 am]