POND ENGINEERING
Pierce’s Park will feature four man made ponds in this beautifully designed urban oasis. Now is a good time to visit the site and see the big digs! There are always surprises in every construction job, but since Pierce’s Park is built in a very old part of Baltimore there is much history to be discovered.
The first surprise was the asphalt layer that was from a parking lot constructed by P. Flanigan & Sons in the 1970’s.
The next surprise was something no one expected: cobblestones!
“This shows you that there was a street here that dates back to the 1800s,” said Bill Beall, Site Superintendent. “The cobblestones came over as ballast in the bottom of the ships that came over from Italy and then we built the roads.” As they were digging Bill also identified what appears to be the outlines of several basements of old row houses that were built very close to the water. They also came across the bulkheads of old piers.
Everything except the cobblestones had to be removed and most of it was recycled. The cobblestones were incorporated into the design of the pond, however, no one will see them as they will be under water supporting its structure.
Every phase of work on the ponds must be certified by the State. Once the hole is sufficiently deep the storm drains need to be installed. The rain will runoff into the ponds, filter through the rocks and sand into the storm drains and finally into the Inner Harbor. Therefore, each phase must be carefully installed in order to keep the water clean.
When workers are in a hole five feet or deeper, a safety box trench is used to protect them.
Six inches of a clean, open stone are placed in the hole. There is no dust on these stones so the water can travel through them.
Four inches of perforated under drain pipes are installed followed by another six inches of open, clean stone.
Three inches of pea gravel, stones that are only 3/8th inch is layered.
A red clay mixture was devised to keep the edges clean.
The last phases will be to add two feet of bio retention soil, specially formulated with organics, mulch, topsoil, sand and ph level tested will be placed next followed by 3” of mulch.
Blog by Helen Szablya
Photography by Steffi Graham
