City Of Baltimore Meets the Challenge Constructing Large Covered Storage Reservoirs

Authors:

  • Remi Urbonas, Art Shapiro, Michael Peterson, Mark Bishop, Rob Ainslie, Reid Campbell

The siting of the proposed tanks.

Many large cities in the US used open drinking water storage reservoirs as it was generally accepted practice in the early parts of the last century – well before modern drinking water regulations. Eliminating them has been part of the Long Term 2 Enhanced Surface Water Treatment Rule (LT2) which has presented many challenges with regard to design and execution. Mostly due to the fact that the significant infrastructure built around the old reservoirs is old; and decades of development make space for construction limited and maintaining operations a challenge.

The City of Baltimore is now undertaking several unique and challenging projects to provide covered storage. One of these projects is replacing approximately 270 MG of drinking water storage provided by the Ashburton Reservoir, originally constructed in the early 20th century, with 50 MG of storage in two new buried concrete tanks adjacent to the reservoir site in Hanlon Park in order to conform to the current regulatory drivers.

The City determined that construction of replacement storage facilities at a higher initial construction cost was preferable to providing UV treatment of water flowing from the existing reservoir – based on a long term vision for water quality, reliability and security. The construction of the new storage facilities replacing the Ashburton Reservoir is part of a larger LT2 compliance program in the City which will reduce the total volume of storage in the system by 51% and total storage surface area by 32%. Design challenges included: identifying measures to accommodate the system-wide operational adjustments necessitated by the LT2 tank construction program; protection of the existing Ashburton Reservoir dam as well as neighboring residential and historical structures during the extensive earth and rock removal activities; architectural conformance to City historic preservation commission requirements due to the close proximity to the historic Ashburton Pumping Station; maintenance of drinking water storage and operation of critical systems during construction.

Following completion of the proposed tanks, Hanlon Park will be restored and improved to provide additional and significant community recreational opportunities to the neighboring community. The Ashburton Reservoir itself will be converted to a pleasing water feature within the park (as it has since the early 1900s) following its retirement from serving as a potable water storage facility. This presentation will review the many aspects of converting open drinking water storage reservoirs to closed tanks, and the schedule, associated construction challenges and costs.

For more information, please contact the author at mpeterson@hazenandsawyer.com.

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