Mather Mill: A Model for Developing Resiliency for Historic Properties

Mather Mill, an early 19th-century gristmill in Whitemarsh Township located in a floodplain, is an at-risk property that served as the test case for the Pennsylvania State Historic Preservation Office’s Disaster Planning for Historic Properties.
Pennsylvania Historical & Museum Commission

The Pennsylvania State Historic Preservation Office (PA SHPO), a bureau of the Pennsylvania Historical & Museum Commission (PHMC) that administers federal and state programs for protecting historic properties in the commonwealth, hosted a demonstration workshop on October 3, 2018, to explore resiliency options for Mather Mill, a National Register–listed gristmill constructed circa 1820 in Whitemarsh Township, Montgomery County. The workshop was conducted as part of PA SHPO’s Disaster Planning for Historic Properties (DPHP) initiative, a program developed with a grant from the National Park Service that is made available to states impacted in 2012 by Hurricane Sandy.

The lion’s share of DPHP has involved identifying at-risk historic resources and, to the extent possible, measuring those risks. PA SHPO partnered with four pilot counties spread across Pennsylvania — Philadelphia, Bedford, Monroe and Cameron — to do a comprehensive survey of at-risk historic properties, collect hazard data, and use that data to update their County Hazard Mitigation Plans.

This demonstration workshop provided an opportunity for PA SHPO to narrow its focus. The office invited architecture and planning firms from throughout the region to attend a one-day workshop dedicated to learning about a single, specific property—its particular history, risks and opportunities — and brainstorm possible resiliency solutions and ways to scale them to other at-risk properties.

Mather Mill was PA SHPO’s target property. The mill is representative of a common property type that is, by definition, near and potentially at risk from water. Located in a declared Sandy county that had not been addressed previously by DPHP, this workshop also provided an opportunity to have a targeted event in a county where a full survey was not conducted.

Mather Mill is also a commonwealth-owned property in need of a new use. Both the mill and nearby properties are in the 100-year floodplain, and the mill has flooded several times since the commonwealth acquired it in 1966. The commonwealth plans to eventually transfer ownership of the property but no specific client or program currently exists. Any new owner, however, would be subject to a covenant and project review by PA SHPO.

Damage to the interior of Mather Mill from previous flooding. Photo, Pennsylvania Historical & Museum Commission

A property immediately across Mathers Lane that was recently acquired by Whitemarsh Township was included as part of the workshop’s scope. Two residential structures on the property that had flooded multiple times were purchased and demolished. The property is subject to Federal Emergency Management Agency deed restrictions that require it to remain as open space. This does allow for some minimal development but only if that development itself supports the continued use of the property as open space.

The day of the workshop started with an introduction to the DPHP program from PA SHPO director Andrea MacDonald. Presentations included a brief overview of the National Park Service’s standards and guidelines for rehabilitating historic properties, contextual background on the Wissahickon Valley Watershed, and floodproofing techniques and how they might impact historic properties.

In addition to the subject-matter experts who gave presentations, a few more people were available for an afternoon discussion. Two members of the Friends of Hope Lodge, which manages the historic Georgian mansion Hope Lodge in nearby Fort Washington and also cares for Mather Mill for PHMC, provided an on-the-ground perspective and possible options for the mill’s future use. Justin Spangler, a water resources engineer with LandStudies Inc., spoke at length about floodplain restoration, and his input spurred an extended conversation. The quality of a discussion like this is a direct result of the people involved, and Spangler, along with Ernie Szabo from the Pennsylvania Emergency Management Agency, provided a valuable source of information that had not been specifically addressed in the morning presentation.

Following the workshop, the firms were given two weeks to create design proposals for use and resiliency at Mather Mill and suggest strategies for scaling those proposals to other at-risk properties. The firms were given substantial format flexibility. PA SHPO wanted to see a variety of design approaches, visual styles, and ways of prioritizing the issues at play.

PA SHPO received materials from five firms: Mark B. Thompson Associates of Philadelphia, Seiler + Drury Architecture of Norristown, BWA Architecture + Planning of Philadelphia, Heritage Design Collaborative of Media, and Vitetta of Harrisburg.

Workshop attendees inspect the interior of Mather Mill. Photo, Pennsylvania Historical & Museum Commission

Each firm restated the problem as they interpreted it. For some, this represented a substantial portion of their submission. This was not unintended. PA SHPO solicited architecture firms specifically for their facility for visualizing problems. With more time to dedicate to a single property and trained design professionals, new ways to effectively visualize risk could be explored.

Mitigating flood risk through site intervention was also a large part of most submissions. In one example, BWA Architecture + Planning recommended rerouting Mathers Lane to unify the Mather Mill property and the township property into a more continuous floodplain. Seiler + Drury recommended a constructed wetland in the township property with improved connections to the creek through the mill’s original raceway.

Each proposal suggested a different level of intervention to the building itself. To maintain Mather Mill’s historic integrity, none of the firms proposed particularly radical alterations. Some included minimal interventions and relied on temporary, easy-to-remove fixtures, displays and bathroom facilities. The proposal from Seiler + Drury included the most substantial alterations to the mill, with recommendations including infilling the basement, creating a new third floor, and building a rear addition at the mezzanine level to house restrooms.

In addition to producing solutions specific to Mather Mill, participating firms were asked to address how those solutions could scale to other buildings and communities in Pennsylvania. Heritage Design Collaborative recommended creating a taxonomy of properties to quantify historic significance and hazard risk.

Although the question of how to scale resiliency solutions received less focus than solutions specific to Mather Mill, it remains PA SHPO’s central concern. Continuing to develop strategies for Mather Mill or any other individual property has independent utility but generalizing this approach so that it is applicable to as many at-risk buildings as possible is ultimately PA SHPO’s goal. In the near term, this workshop was conceived of as a prototype: What lessons can be learned that can be applied to the next event?

The greatest lesson PA SHPO took from the day’s experience is the importance of enthusiastic partners. The next workshop will not focus on a commonwealth-owned building, so working with a property owner that is passionate about the process is more imperative than the property selection itself. The risk of flooding applies to a vast array of homes, businesses and institutions in historic communities, and each deserves the attention this type of workshop brings.

For more information on Disaster Planning for Historic Properties and to view the five Mather Mill submissions, visit phmc.pa.gov/Preservation/Disaster-Planning.

John Gardosik manages the Disaster Planning for Historic Properties initiative for the Pennsylvania State Historic Preservation Office.