Control Estanques Agua Potable

_____________________________________________________________________
Office of Water (4601M)
Office of Ground Water and Drinking Water
Distribution System Issue Paper

Finished Water Storage Facilities

August 15, 2002

PREPARED FOR:
U.S. Environmental Protection Agency
Office of Ground Water and Drinking Water
Standards and Risk Management Division
1200 Pennsylvania Ave., NWWashington DC 20004
Prepared by:
AWWA
With assistance from
Economic and Engineering Services, Inc

Background and Disclaimer
The USEPA is revising the Total Coliform Rule (TCR) and is considering new possible
distribution system requirements as part of these revisions. As part of this process, the
USEPA is publishing a series of issue papers to present available information on topicsrelevant to possible TCR revisions. This paper was developed as part of that effort.
The objectives of the issue papers are to review the available data, information and
research regarding the potential public health risks associated with the distribution
system issues, and where relevant identify areas in which additional research may be
warranted. The issue papers will serve as background materialfor EPA, expert and
stakeholder discussions. The papers only present available information and do not
represent Agency policy. Some of the papers were prepared by parties outside of EPA;
EPA does not endorse those papers, but is providing them for information and review.
Additional Information
The paper is available at the TCR web site at:http://www.epa.gov/safewater/disinfection/tcr/regulation_revisions.html
Questions or comments regarding this paper may be directed to TCR@epa.gov.

Finished Water Storage Facilities
1.0

Introduction

The goal of this document is to review existing literature, research and information on the
potential public health implications associated with covered storage reservoirs.
Finished water storage facilities are an important component of theprotective distribution system
“barrier” that prevents contamination of water as it travels to the customer. Historically, finished
water storage facilities have been designed to equalize water demands, reduce pressure
fluctuations in the distribution system; and provide reserves for fire fighting, power outages and
other emergencies. Many storage facilities have been operated to provideadequate pressure and
have been kept full to be better prepared for emergency conditions. This emphasis on hydraulic
considerations in past designs has resulted in many storage facilities operating today with larger
water storage capacity than is needed for non-emergency usage. Additionally, some storage
facilities have been designed such that the high water level is below the hydraulic grade lineof
the system, making it very difficult to turnover the tank. If the hydraulic grade line of the system
drops significantly, very old water may enter the system. If tanks are kept full yet are
underutilized, the stored water ages and water quality is affected.
The main categories of finished water storage facilities include ground storage and elevated
storage. Finished water storage does notinclude facilities such as clearwells that are part of
treatment or contact time requirements per the Surface Water Treatment Rules. Ground storage
tanks or reservoirs can be below ground, partially below ground, or constructed above ground
level in the distribution system and may be accompanied by pump stations if not built at
elevations providing the required system pressure by gravity.Ground storage reservoirs can be
either covered or uncovered. Covered reservoirs may have concrete, structural metal, or flexible
covers. The most common types of elevated storage are elevated steel tanks and standpipes. In
recent years, elevated tanks supported by a single pedestal have been constructed where aesthetic
considerations are an important part of the design process. A standpipe is...