In my last installment of this blog, I discussed the unusual steel & concrete construction of pier 5. This pier’s support is dense with closely placed steel piles. I speculated on the intertidal zone reef which has formed through it over its 80 year existence and which sustains an increasingly healthy aquatic environment as I have continued to regularly observe it over the past 30 of those years. This week I turn my attention to the shoreline from which the pier extends. As residents and visitors to the harbor walk are well aware, the buttressed shoreline has had issues in recent years. Sink holes at the traffic circle at the base of pier 4 near the pumphouse Building 123 have undergone extensive restoration work this past fall and a section of the harbor walk on pier 4 adjacent to the ferry docks required a structural rebuild that is just now being completed in time for Spring. 2021. Ground settlement has occurred periodically and is currently present along the harbor walk by pier 5 as well as in the lawn waterside of Shipway Place between piers 7 and pier 8.
The Admiral’s House in the Navy Yard uphill from the USS Constitution is surrounded by 19th Century Hardwoods and rests on the lower slopes of Breeds Hill which is home also to The Bunker Hill monument. It lies well above the high tide lines. The dry docks 1 &2 and the shoreline extending to Pier 8 under the harbor walk are all filled tidal wetlands dating back to the 19th century. Much of the working Naval Yard was constructed on this fill. The elevation of the filled tidal wetland varies, but for the most part is above the maximal flood tides experienced over 50-year periods. In January 2019 a severe Nor’easter moving by slowly just offshore at a period of astronomical high tides. This brought sea water over the lip of Dry Dock 2 at its base end near First Avenue and flooded that lowest segment of that flat appearing street. The sea also rose just above pier 8 at 13thStreet and the harbor walk in front of Shipways Place. It did not however, reach the surface levels of piers 4,5, or 6, Eighth Street or the harbor walk adjacent to pier 5.
The shoreline itself which runs under the harbor walk is constructed of carefully placed granite slabs dating back to the 19thcentury. In some sections steel plates have been added to or replaced the granite. Drydocks 1 &2 are of also 19th century granite construction excavated below the low tide line so that ships with drafts greater than Boston’s 10 foot tidal range can be floated in at very high tide. A dry dock of course is pumped dry and must have its upper edge above the maximal flood tide when it is in service with a dismantled ship in the dock undergoing repair. Otherwise the dry dock would flood the work site. Under the streets of the Navy yard, there is a network of tunnels and storm drains. Tide water can enter some of these so that a rising tide may emerge from a storm drain before it breaches from the shore edge. I am unaware of a tide ever breaching the drydock 2 when it was in service, but that would have happened in January 2019 as the accompanying photo demonstrates.
Flagship Wharf was constructed in 1987 as a renovation of the large Federal Building 197 that had served as the administrative headquarters of the Navy yard. Part of the reconstruction included the excavation of a multilevel below ground parking garage that extends 5 floors down to below the level of the harbor floor. Water depth at Pier 5 is about 45 feet at mean high tide. The garage is constructed with a slurry wall set back from the granite and steel seawall and surrounded by remaining 19th century land fill. The footprint of the slurry wall extends outside the base of the shoreside of the building for its entire width. Juxtaposed to this slurry wall, pier 5 represents a massive steel “reef structure” that buttresses the land fill and seawall adjacent to Flagship wharf. When the pier was constructed, closely placed steel piles were driven into the seabed and then coated in concrete where they have rested now for 80 years.
Strong southerly winds blow the several mile length of the inner harbor on hot summer days when afternoon south westerlies pick up and are even stronger when fronts approach or when low pressure passes to the west of Boston. Under these conditions large waves can rapidly pick up and directly impact the northern prominence at pier 5. This is the most exposed shore on the north side of the harbor. The force of these waves is broken by the dense piles which reduces the erosive force of the waves on the granite seawall shoreside. However, the seawater does flow through the granite sections and slowly with the motion of the waves, the outgoing tides extracts fill from the space behind the granite. This continuous harbor action results in the ground settlement and sink holes previously noted that recur on an ongoing basis along the section of the Navy Yard.
The environmental consequence of removing the legacy pier 5 is significant. In the previous installment, I discussed the aquatic habitat that the pier has created. Perhaps even more important to area residents is the pier’s role in buffering the action of the sea. If tides like that of January 2019 and even higher recur frequently as is expected, it will become necessary to further elevate the height of land along the Navy yard waterfront. Demolition of the pier, as is the current mandate of the BPDA RFP, will remove this buffer and replace it either with a floating dock or a reconstructed pier that will not have the density of steel serving as both marine habitat and tidal buffer. The consequences to both the integrity of the harbor walk and the parking garage below Flagship and the aquatic biosphere may be substantial and harmful.
As I concluded also last week, funds for preservation of the pier and reef and its structural reinforcement to allow for light service duty as an educational and living outdoor natural exhibit as part of a coastal resiliency demonstration should be secured and the pier preserved as a great community asset. The assertion that under all circumstances the pier must be demolished and removed with no alternative must be questioned and the rationale closely scrutinized. There may be satisfactory alternatives worthy of implementing.
Certainly, Imagine Boston 2030as an updated city masterplan has revised the visions originally articulated in earlier municipal harbor plans and its guidance is now consistent with chapter 91 concepts regarding the tidal water sheet. I would argue the vison of Imagine Boston 2030 should drive the future of this unique and special community place, not the plan cited by the BPDA that dates back to 1978.
Applying letter of the law compliance achieved by the weaseling through inconsistent regulatory language to implement plans that are inconsistent with the community will and the best interest of the people of Boston, should not be taken countenanced. Let us imagine creative solutions for the revitalization of pier 5 and celebrate its value as an aquatic sanctuary, shoreline buffer, and educational resource on a beautiful and dynamic activated waterfront.
Chris Nicodemus, 4 March 2020
· Flood zones in the Navy Yard
· The Sea wall at pier 5 (credit N Sneh)