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Nebraska communities partner to plan: a Papillion Creek Watershed Planning Project in eastern Nebraska has been a success because it has established the tools needed for long-term watershed planning and assessment.

Several communities and two counties in eastern Nebraska have joined forces to improve water quality in the Papillion Creek Watershed and facilitate the Phase II EPA stormwater permitting process. The Papillion Creek Watershed consists of 402 square miles of drainage area, with a complex mixture of urban and rural agronomic land uses.

New growth in the densely populated area--the three counties in the watershed represent more than one-third of the state's population--is currently consuming approximately 41/2 square miles per year, causing increased imperviousness and higher resultant surface runoff and water-borne pollution. The Nebraska Department of Environmental Quality has placed many of the area reservoirs on its 303(d) impairment list for sediment and nutrients, and the lower, urban segments of the Big Papillion Creek are listed as impaired for pathogens (fecal coliform contamination).

The consequences of such impairment listings will be the issuance of corresponding Total Maximum Daily Load (TMDL) determinations. TMDLs involve a rather complex process of deriving "safe" allocations of "point" and "non-point" pollution for a particular contaminant. TMDL determinations, in turn, are intended to provide the regulatory basis for either voluntary best management practices or enforceable compliance through the issuance of discharge permits. Therefore, such pollution sources as existing combined sewer overflows (CSOs), concentrated animal feeding operations, active construction sites, and others are problematic with respect to their negative impact on recreation, aesthetics, and fisheries on the streams and reservoirs throughout the watershed.

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PLANNING PARTNERS

In August 2001, nine cities within the watershed formed a partnership with officials from the Papio-Missouri River Natural Resources District (P-MRNRD), Douglas County, and Sarpy County to discuss key surface water issues and facilitate the regulatory processes on a watershed-wide basis.

Dubbed the Papillion Creek Watershed Partnership, the group meets monthly to address impairment issues in a community-based, watershed-specific manner, aimed at producing cleaner water while sharing resources. The assistant general manager for the district, Marlin J. Petermann, P.E., sees benefits in the partnership. "Utilizing the watershed approach makes sense to the partnership members. Some of them could make tremendous strides toward addressing their own stormwater issues, but yet have very little impact on the overall water quality in the basin," he says.

Among the goals of the Partnership is to identify the probable sources and extent of targeted pollution and recommend realistic best management practices that can have mutual benefits among the various regulatory programs.

According to Robert Sink, environmental services manager for the City of Omaha, "The major challenge in the beginning (1999) was educating some of our partners on the regulations that were going to affect their communities directly in the near future and how we as a watershed could effectively and efficiently address those regulations," he recalls.

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CHALLENGES MOUNT

The Phase I inventory presented serious challenges to the project team and required 4 to 5 months for collecting and piecing together all information and accurately discerning follow-up action items.

Land use information existed in several forms that had to be put in a GIS format with common land use categories and a 2040 planning window. Hydrology and hydraulic (H & H) information was also difficult to gather, due to age.

Gathering information that could be applied to best practices under EPA regulations required a concerted effort among all the partners. Progress was accelerated using the concept of an innovative, standardized Notice of Intent/Permit Application template, created by HDR and the Partnership.

A master database was created for tracking proposed best practices projects and related Stormwater Phase II compliance activities, such as site inspections and project photos. This tied the information relationally to water quality-related data and to the existing GIS mapping.

The H & H modeling efforts for the Papillion Creek basin involved the conversion of outdated, unsupported computer models to the latest U.S. Army Corps of Engineers models. The Corps' efforts are known as Nex-Gen models, referring to a new--or next--generation of modeling techniques. This includes models that can accept GIS-based information, real-time rainfall data, and advanced dynamic routing routines.

Then, the Nex-Gen models were calibrated to 19 rainfall/streamflow gauges placed within the basin. Three high-intensity rainfall events were captured and reconstituted within the models. At the end of the calibration process, the models were used to estimate both existing and future flood flows, volumes, and stages (levels).

To more easily explain the complex H & H and water quality modeling findings, a series of color gradient watershed maps were created that clearly show the "hot spots"--impacts from the metropolitan area growth and changes in land use. These findings suggest that an aggressive program of surface runoff attenuation must be continued to mitigate future flooding and erosion problems.

Several forms of water quality modeling were used to assess both present and future fecal coliform contamination within the watershed: historical trend line evaluations by both time and stream mile; statistical regressions, mass loading analyses; and dynamic modeling. A facilitated selection process with City of Omaha and P-MRNRD staff was used to evaluate and select the best dynamic modeling approach for the multiplicity of the water quality issues. The initial focus was on dynamic simulation of bacteria with linkages to the H & H modeling and GIS mapping.

The Water Quality Analysis Simulation Program (WASP5) was selected for use in this analysis. WASP5 is capable of 1-, 2-, and 3-D representations and dynamic simulations. It can simulate bacteria concentrations as well as a variety of other water quality parameters, including sediment. The integration of the HECHMS and HEC-RAS, and WASP5 models, although not seamless, is facilitated using a relational database that links them together.

DIFFICULT ISSUES LOOM

Modeling for fecal coliform bacteria demonstrated that bacteria levels are highly dependent on surface runoff and sediment transport events. Levels exist well above the state's surface water quality standards for primary contact recreation for the majority of the watershed--even above the metropolitan area.

It is possible that background fecal coliform levels from wildlife alone may be higher than standards currently allow, which would raise troublesome questions from a regulatory enforcement perspective. As a result, it will take a concerted effort among stakeholders and innovative inter-jurisdictional financing to methodically implement best practices to mitigate the H & H and water quality impacts from growth.

For his part, Sink is equally impressed. "Regardless of the size of the jurisdiction, the challenges and hurdles to overcome are remarkably similar, differing primarily on the scope," he says. "The common solutions can therefore be uniformly developed and applied to all communities. This commonality should result in lower costs to the communities and the entities affected by the new requirements."

--This article was adapted from the winter 2003 issue of Waterscapes, a publication of HDR. Christensen, the firm's manager for this project, can be reached at 402-399-1329 or e-mail lychrist@hdrinc.com.

By Lyle Christensen, P.E.
COPYRIGHT 2003 Hanley-Wood, Inc.
No portion of this article can be reproduced without the express written permission from the copyright holder.
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Title Annotation:Watershed Management
Author:Christensen, Lyle
Publication:Public Works
Date:Dec 1, 2003
Words:1134
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