by John Amodeo
Sustainable design measures in the landscape are often highly visible: rain gardens, cut-off light fixtures, tree shaded walkways. But if you walk through the Christian Science Plaza, whose comprehensive restoration was led by Arcadis IBI Group, the primary sustainable interventions are mostly invisible but nevertheless meet The First Church of Christ, Scientist’s goal of making this historic urban plaza more sustainable.
The Plaza was designated a Boston Landmark in 2011, subjecting it to review and approval by the Boston Landmark Commission, limiting opportunities for major surface alterations. Consequently, many sustainable design strategies had to be kept out of view.
Some sustainable gestures are evident, such as enlarging the Massachusetts Avenue lawn, reducing impervious surfaces, and mitigating heat island impacts. But the site’s water management, a huge undertaking, is largely invisible. If the plaza’s paving and lawn were transparent, like the educational toy “The Visible Man/Woman,” which allows you to see the underlying human anatomy through its clear skin layer, the complex systems managing stormwater and potable water consumption would be visible.
Prior to the plaza restoration, the church’s annual potable water consumption was 13 million gallons, primarily through building usage, but also to accommodate the Reflecting Pool, the Children’s Fountain, landscape irrigation, and to artificially recharge retreating groundwater beneath The Mother Church Original (TMCO) and The Mother Church Extension (TMCX) edifices using injection wells to avoid exposing structural wood piles to potential rot. The plaza also generated 14 million gallons of stormwater runoff annually that was captured in pipes and discharged into the Charles River. The situation was not sustainable.
The multi-disciplinary team led by Arcadis IBI Group incorporated discreet strategies to better manage water on the site while respecting the plaza’s historic design. To reduce water consumption, the team eliminated the reflecting pool’s leaking into the garage below by deconstructing the pool, waterproofing the garage roof, and then reconstructing the pool to its original appearance. Furthermore, the team reduced the original pool depth from 27 to 8 inches. Thus, the team reduced the reflecting pool’s annual potable water demand from 3 million gallons to 800,000 gallons.
Buried beneath the enlarged Massachusetts Avenue Lawn are a group of open pipe galleries and cisterns that store/treat stormwater runoff and recharge retreating groundwater. The galleries beneath the lawn have been sized to handle the first inch of stormwater runoff from within the plaza. A 25,000-gallon holding tank slow-releases captured stormwater into the galleries. A 25,000-gallon dechlorination tank in the Publishing House basement purifies the reflecting pool overflow before it goes into the lawn’s recharge galleries, and a 12,500-gallon day tank treats pavement and roof runoff before sending it into the injection wells that hydrate the wood piles beneath TMCO/TMCX.
Post-restoration, the church’s annual potable water demand has dropped from 13 million to 9.6 million gallons, the injection wells’ potable water consumption has dropped from 700,000 gallons annually to zero, and the plaza’s annual stormwater runoff has been reduced from 14 million to 7.1 million gallons.
As the public is welcomed back into this newly restored landmark, they will enjoy its numerous visible amenities. But without a transparent ground plane that would provide a glimpse into the invisible landscape, few will be aware of the activity hidden beneath the surface that make the Christian Science Plaza as sustainable as it is iconic.
John Amodeo, FASLA is a principal with Arcadis IBI Group.