Emergency Action Plan Updates for 10 High Hazard Dams Owned by the Massachusetts Department of Conservation and Recreation (DCR)

Challenge

In August 2021, GZA was retained by the Massachusetts Department of Conservation and Recreation (DCR) to update Emergency Action Plans (EAPs) for 10 of DCR’s dams in Massachusetts.  The dams, classified as High Hazard, had existing EAPs, which had been originally developed in 2013/2014 and were last updated in 2018. Five of the dams were grouped into a single EAP, resulting in a total of 6 EAPs to update. 
 

Solution

GZA reviewed the existing EAPs. GZA checked that the EAPs fulfilled the requirements listed in the Massachusetts Rules and Regulations and generally followed FEMA-64 (Federal Guidelines for Dam Safety – Emergency Action Planning for Dam, published by FEMA). GZA conducted telephone and email interviews with agencies listed in the EAPs, including DCR, to update the EAP’s contact information. One of the EAPs differentiated in format and had unusual and awkward EAP language. GZA updated this EAP to be consistent with the other EAPs.

For five dams, GZA also reviewed the dam’s existing inundation maps to check for development in the downstream area. GZA used the latest publicly available aerial imagery. For the other five dams, GZA performed dam break modeling. The five dams have the same downstream flow path. GZA estimated which dam’s failure would result in the largest inundation area and performed dam break modeling for this dam. GZA used the DSS-WISETM Lite software, which was developed by the National Center for Computations Hydroscience and Engineering at the University of Mississippi. This FEMA-approved software is hosted online and performs 2-dimensional hydraulic modeling for dam break simulations in the United States. GZA simulated both sunny day and wet weather simulations.

GZA used the ArcMap software to develop inundation maps. The inundation maps show both the sunny day and wet weather inundation areas. The maps also include tables showing the timing of the flood wave, locations of buildings, and the rational for where the inundation map ends. GZA provided DCR and the downstream local emergency management agencies with GIS shapefiles of the estimated inundation area. 
 

Benefit

GZA successfully update the EAPs to meet the requirements listed in the Massachusetts Rules and Regulations.