Evaluation of Contributions of Leaking Water and Sewer Infrastructure in Gwynns Run and Maidens Choice Run to Streamflow in the Lower Gwynns Falls Watershed, Baltimore, Maryland

WRD PROJECT #: MD164
PROJECT CHIEF: Fisher, Gary
BEGIN DATE: 01-July-2001
END DATE: 30-September-2001

Customers currently supporting the project:

City of Baltimore
U.S. Geological Survey

Problem

Gwynns Run and Maidens Choice Run have been identified by Baltimore City as its two most degraded streams. Much of this degradation is attributed to leaking sanitary-sewer lines and sanitary-sewer overflows. Sewage is believed to enter the streams as ground-water discharge or through storm-sewer pipe joints. It is also believed that there are significant inflows of treated drinking water to local ground water from leaking supply lines. The total load of constituents contributed by Gwynns Run and Maidens Choice Run and their relative contribution to streamflow in Gwynns Falls are unknown. Information is needed to help the City to better manage its water resources and satisfy environmental and regulatory concerns. In particular, data are needed to determine appropriate allocations of Total Maximum Daily Loads to point and nonpoint sources in the Gwynns Falls, including those attributed to failing infrastructure.

Failing urban water infrastructure has recently been cited by the American Society of Civil Engineers as a major national issue that will take many billions of dollars to address. Because of the influence of impervious surfaces and leaking water infrastructure, ground/surface water interactions in urban areas are poorly understood. The results of this investigation are expected to provide fundamental information to advance our understanding of urban hydrology. The results will also help to fill a critical information gap for the Baltimore Ecosystem Study (BES) for Long-Term Ecological research in the urban environment.

Objectives

1. Determine streamflow in Gwynns Run and Maidens Choice Run.
2. Evaluate suitability of using selected chemical constituents as indicators of sewage and drinking water contributions to flow in an urban stream.
3. Evaluate suitability of water temperature as an indicator of ambient ground water, sewage, or drinking water contributions to flow in an urban stream.
4. Determine loads of nutrients and selected constituents in Gwynns Run, Maidens Choice Run, and lower Gwynns Falls during low and high-baseflow conditions.

Approach

A follow-up study is proposed for joint funding by Baltimore City and USGS. The lower Gwynns Falls will be monitored from July 1, 2001, through June 30, 2002. For Phase-II, temporary streamgaging stations will be established on Gwynns Run and Maidens Choice Run. Because streamflow data are needed by Baltimore City to determine constituent loads in the lower Gwynns Falls, these stations are proposed regardless of the results of Phase-I investigations. The flow study will also use data from the existing stream-gaging station at Washington Boulevard. The temporary stream-gaging stations will operate through September 30, 2002, to complete the Water Year for data publication, although the proposed interpretive analysis will only use data through June 30, 2002. At the discretion of Baltimore City, these stations may continue operation if new funding becomes available.

Phase-III will run concurrent with the stream gaging of Phase-II, but its final design will depend on the results of Phase-I investigations. Any or all of the parameters being considered may be monitored during Phase-II, and will be determined by consensus. Assuming that all of the parameters are good potential indicators, a conceptual design follows. If Phase-I indicates that any of the parameters are not suitable indicators, the design will be adjusted by consensus among all partners to best utilize project resources.

If Phase-I results indicate that water temperature is a good potential indicator of sewage or treated water contributions to streamflow, continuous monitoring will be done concurrent with stream gaging. Because there are likely to be significant seasonal differences between temperatures of ambient stream water, ground-water discharge, and water discharging from storm-sewer systems, at least eight low-cost temperature recorders will be installed at key locations to test water temperature as a surrogate parameter for detecting ground-water or sewage input.

If Phase-I field reconnaissance suggests that any parameter may be a good potential indicator of sewage or treated water contributions to streamflow, systematic follow-up will be conducted. Synoptic stream surveys-- a "seepage run" --will be conducted during baseflow conditions in Maidens Choice Run during late summer 2001 and again during late winter 2002 to evaluate tributary, storm sewer, and ground-water discharge contributions to streamflow in Gwynns Falls during the seasonal extreme baseflow scenarios. These times are also optimal for testing the water temperature as a surrogate parameter. In addition to streamflow measurements, field parameters will be measured and selected water samples will be collected. Constituents for analysis will be determined by consensus, but will likely include fluoride, caffeine, and human pharmaceuticals as relatively conservative indicators of treated drinking water and sanitary sewage. Analysis will also include nutrients and major ions. Analyses will be performed by the USGS National Water Quality Laboratory.

Selected tracers, such as lithium, may be added by Baltimore City to sewage lines in the study area and will be included in the laboratory analyses.

Chemical analysis of reference water samples from Pond Branch at Oregon Ridge, Gwynns Falls tributary at McDonogh, and Ashburton Filtration Plant raw water will be done to provide background levels for fluoride and major ions.

It will be requested that Baltimore City provide samples of sewage for analysis by USGS to characterize its likely constituents that may be detected in lower Gwynns Falls. Baltimore City will also supply available environmental data and engineering (infrastructure) data that are pertinent to the proposed investigation.

Baltimore City and BES will be provided the opportunity to collect additional samples or perform additional analyses concurrently with field activities in this project. No bacteriological analyses are planned as part of the proposed study, but others could collect concurrent samples for analysis.