Amendment #240 to H4506

South Branch Parkway / Briarwood Ave Storm Drain Improvement

Mr. González of Springfield moves to amend the bill by inserting after Section 2B 6121-2138 the following section:

"SECTION 6121-2142

The proposed Project is for drainage infrastructure and slope stability improvements along a

section of South Branch Parkway. In this area, inadequate and antiquated stormwater

infrastructure constructed in the 1930’s and 1940’s has the potential to cause damage to and closure

of the roadway as well as impacts to the critical utility lines in the roadway (sewer interceptor and

water main). The Project vicinity experienced exponential population and home construction

growth in the period immediately following World War II and is now a densely-developed

residential neighborhood of 1/8- to 1/3-acre lots. The rapid growth contributed to deficiencies in

storm drain infrastructure capacity. The Project concerns replacement of a particularly

troublesome component (manhole and pipe system) that is undersized and in need of improvement.

The South Branch Parkway was developed in the 1920s and 1930s and the connecting streets

contributing stormwater runoff to the Project area were constructed in the 1950s and ‘60s. A major

storm drain was constructed in the Project area, to which several additional storm drains were

added during the period of rapid growth. The terminal section of storm drain prior to its discharge

to Watershops Pond is a 48”-diameter concrete pipe. At the immediately-upstream drain manhole,

which is over 22’ deep and constructed of brick and block,, at the intersection of Briarwood

Avenue and South Branch Parkway, five (5) storm drains with a combined capacity of

approximately 180 cubic feet per second (cfs) combine and discharge to the terminal section of

drain pipe, which has a capacity of approximately 150 cfs. The capacity imbalance is exacerbated

by inefficient manhole hydraulics, resulting in added head loss and reduced overall capacity. This

high rate of inflow into the manhole, in conjunction with the type of manhole conjunction, has

caused some structural failurs at inflow locatins into the manhole. The City has has made necessary

interim repairs t structurally support the manhole structure, until the entire structure can be

replaced. In short, the final link in the storm drain chain is inadequate and in failing condition,

and is in need of improvement to maintain the effectiveness of the storm drain infrastructure. The

Project area and the contributing stormwater drainage catchment area were significantly affected

by an EF-3 tornado on June 1, 2011, which resulted in a federal disaster declaration in the City.

Many homes in the area were damaged or destroyed, and virtually the entire tree canopy within

the contributing watershed was a total loss. This resulted in a loss of a substantial tree canopy that

had grown to maturity since the original developments 50-60 years ago. The loss of canopy

resulted in a significant alteration of the hydrologic characteristics of the drainage catchment area,

and significantly- increased stormwater runoff. Coupled with observed increasing storm intensity,

this has resulted in additional stress on already inadequate stormwater infrastructure. Since the

tornado, the weakest section of storm drain has experienced substantial and repeated surcharging

and continual signs of partial failure due to the hydraulic stresses. The drain manhole has begun

to deteriorate and the sinkholes regularly appear at the ground surface adjacent to the South Branch

Parkway, necessitating interim maintenance until the system can be improved with additional

hydraulic capacity. South Branch Parkway has a thin shoulder in this location and then a steep

embankment slope down to the surface of Watershops Pond. Additionally, a large sanitary sewer

interceptor (36” diameter) that services several areas of Springfield including the Sixteen Acres

neighborhood and portions of the adjoining Town of Wilbraham traverses over the “weakest link”

section of storm drain. A 10-inch cast iron water main also traverses over the storm drain. The

roadway embankment, the sewer interceptor, and the water main are all expected to be severely

impacted by a failure of the overtaxed storm drain infrastructure. The proposed Project would

improve the overall resiliency of the municipal infrastructure by replacing the terminal manhole,

inflow storm pipes and final 80± foot section of storm drain pipe with structures of greater capacity

designed to accept and safely convey stormwater runoff from the contributing drainage catchment

area, accounting for the altered landscape and increasing storm events from climate change.

Total Project Cost: $2,000,000