Subterranean Resiliency: Predicting, Assessing and Mitigating Saltwater Intrusion

Subterranean Resiliency:
The Hidden Threat of Saltwater Intrusion and a Model for Mitigation
 
Even in Southeastern Massachusetts where we can boast of deep deposits of pure, glacial water, we are discovering that our sole-source aquifer is vulnerable, vulnerable to both existing development and withdrawals, to overuse, and in the foreseeable future to the potentially catastrophic effects of climate change and sea-level rise.
 
Saltwater intrusion (SWI) is both a symptom of that vulnerability and a cause.
 
Unchallenged, changes in the fresh/saltwater interface can lead to the failure of septic systems, interfere with underground wires and piping, destroy the ecological viability of rare coastal plain ponds and their associated species and create critical shortages of drinking water.
 
The signs are there. A once pristine coastal plain pond within the climate justice community of White Horse Beach has seen its water quality deteriorate dangerously, cyanobacteria blooms appear, necessitating beach closures and a quarter of a million-dollar expenditure to try and identify the causes. Several of the town’s well pressure zones are presently operating at a deficit (more water out, than in), restricting development and putting pressure on the town to develop more wells even as concerns for the effect of those withdrawals on freshwater ponds increase. A 2015 collapse of the town’s municipal sewer pipeline required a three-year, $45 million dollar fix and that system only served a quarter of the town’s residents.
 
100% of the town’s nearly 60,000 residents rely on the area’s sole source aquifer for potable water which, if saturated with salt water, would be like a neutron bomb: leaving pipes and wells intact while rendering the water itself unpotable.
 
We are a far cry from that day but do not have to look far to find communities that are suffering from their slow response to the causes and effects of SWI.
 
More than 40 states in this country are fighting this battle.
 
In Hawaii, the addition of small in number but large in the aggregate new wells has jeopardized a sacred indigenous site, its saltwater pond, and associated rare plant species.
 
In Washington state private wells are now regularly tested for SWI and where the intrusion is documented owners are required to perform additional annual testing.
 
Existing resiliency models in Massachusetts outline a variety of threats for Plymouth including surges due to sea-level rise and hurricane surges all of which are consequential and will need to be addressed. But that ‘top-down’ approach does not acknowledge the subterranean threat of SWI.
 
Even when the seas are calm and shore roads dry the effects of SWI may be underway.
 
Largely through the work of the US Geological Survey (USGS Masterson Model), there is a great deal known about the basic hydrogeology of the Plymouth area, and of adjacent coastal communities in Southeastern Massachusetts and on Cape Cod. But that data has not been applied to the question of SWI.
 
To do so, with accuracy, requires further refinement of those existing hydrogeological models, water sampling across varying topographies and several drainage basins, and the combination of that data with projections on population, sea-level rise, climate change, and other factors.
 
That refined model, (sifted by the UMass Supercomputers) will allow for the development of a new model geared to produce what you might call “subterranean resiliency.”
 
That scientific goal will be coupled with a 2-year, town-wide water conservation education and outreach program that will take as inspiration the indigenous perspective of the award-winning book, “We Are Water Protectors” to instill an appreciation of the value of water to our lay audience.
 
Each of this projects’ partners has its own unique commitment to resiliency.
o  The Town of Plymouth’s coastal setting and unique ecological attributes are inseparable and have already prompted a series of innovative efforts that have removed dams, restored cranberry bogs, re-established herring runs and increased the resiliency of ponds, rivers, estuaries and beaches.
o  The Living Observatory was founded on a belief in the, then unproven idea that resiliency can be restored: they were responsible for the nationally-acclaimed Tidmarsh Cranberry Bog restoration, and for their commitment to making those natural restorative processes visible to the layperson.
o  The Southeastern Massachusetts Pine Barrens Alliance has established working relationships with most of the leading environmental nonprofits in Massachusetts in the cause of preserving the area’s globally-rare ecoregion, has received nationally competitive grants, and recently established a regional environmental discovery center that will serve as the conference center and citizen-science laboratory for this project.
o  The Plymouth Area League of Women Voters has an established reputation as a proponent of civic engagement, has demonstrated a commitment to social and environmental justice and represents a national organization with a deep commitment to climate issues.
o  The Plymouth Water Conservation Committee has a simple goal that, if realized, will create an opportunity to plan for the community’s resilient future, not simply react to water crises as they occur.
 
Town staff and members of these established organizations will work within a historic indigenous landscape, on a philosophical foundation that is nearly as old as our globally-rare ecoregion. For the Wampanoag people the lands on which they live and the natural resources on which they depend are inseparably linked to their identities, cultures, and livelihoods: who better to spearhead our outreach and education efforts than the region’s native peoples.
 
With an informed citizenry and an enlightened bureaucracy we hope to be able to:
o  guide the design and location of future municipal water systems
o  increase the resiliency of established water sources
o  establish citizen-scientist sentinels to sound the SWI alarm if and when
o  identify cost-effective nature-based solutions for these unnatural upheavals and, finally,
o  add important data to the debate over which climate resiliency strategies will be most effective for Massachusetts’ coastal communities in the future.
 
The Town of Plymouth
The Living Observatory
The Southeastern Massachusetts Pine Barrens Alliance
The Plymouth Area League of Women Voters
The Plymouth Water Conservation Committee
The Indigenous Resource Collaborative
The Herring Pond Wampanoag Tribe