OCWA—Central New York’s Water Authority—received awards from the American Public Works Association’s New York Chapter, Central Branch (APWA) for several innovative construction projects at the APWA’s annual awards dinner held on November 17, 2016 in Canastota.
Otisco Lake Dam Rehabilitation
OCWA received the 2016 Structures Project of the Year Award from APWA for its rehabilitation of the Otisco Lake Dam. While the dam was recently evaluated and found stable and safe, there were insufficient details to estimate how the dam would perform during an unforeseen catastrophic event (i.e. Hurricane Sandy). To be conservative and to ensure the long term stability of the dam, OCWA chose to install additional anchors that will secure the dam in place for the long term.
One key focus of the project was to limit the impact on lake levels. A highly sensitive topic, Otisco Lake is regarded as a valuable recreational resource to the local residents. Additionally, lake level directly impacts OCWA’ s ability to produce water at our downstream water treatment plant and lowering lake level would be a direct impact on the ability to maximize our most efficient water source.
The major work occurred in the fall which coincided with the historically lowest lake levels during the year. The work included:
- Design of a restraint system that would improve the dam’s stability to sliding and overturning. The design had to account for the fact that the dam is actually comprised of two structures; the original masonry dam from 1908 and the upgraded cast-in-place concrete overpour from 1963. Both of which sit atop wood piles from 1908.
- Drilling 100-foot-long anchors at an angle through the concrete and masonry dam and into the lake bed below. Precise location and angle of the anchors was necessary to avoid several existing structural features of the dam including steel sheet pile walls beneath the upstream toe.
- Installation of load cells to monitor select anchors for confirmation of construction and for the long term stability of the dam.
- Petrographic analysis of the existing masonry grout to establish the original mix design and replicate it with the goal of achieving similar strength and performance to the original. The replicated grout mix was then used to hand re-point all of the dam exterior masonry joints.
The overall project was completed on-time and under budget. Despite the potential for many complications, the work progressed smoothly. Strong cooperation between the contractor (M. Hubbard Construction, Inc.), OCWA and the engineer (CHA Consulting, Inc.) allowed for steady progress.
Transmission Main and Streambank Repairs Project
OCWA also received the 2016 Emergency Project of the Year Award from APWA for its reconstruction of stream banks along Nine Mile Creek to stabilize large diameter transmission mains. The mains convey raw water from Otisco Lake to OCWA’s Water Treatment Plant in Marcellus and finished water from the plant to Fairmount and beyond. The oldest main dates back to 1909 and the newest 1963. Over the years the creek has continued to meander and change course. At several locations this change has resulted in erosion of the stream bank and old rail bed and exposure of the one or more of the transmission mains. Left unaddressed, the mains would collapse as the creek successfully undermines its bedding. To prevent failure of the transmission mains and ensure the long term stability of the system it was necessary to reconstruct the stream banks and stabilize it for the long term. This project encompassed four sites along the creek between Marcellus and Camillus, New York.
The design had to achieve a balance between durable protection of the transmission mains and proper restoration of the creek bank. The designs developed for each site incorporated a robust armoring of the stream bank to prevent continued erosion and protect the mains. Where mains crossed through the creek, the designs incorporated articulated concrete mats and stone. They also incorporated the creation of natural in-stream features such as pools and riffles to restore the stream habitat and flow characteristics. Natural features of the stream were identified prior to the work and recreated after the work to limit the impact to existing habitat. Permitting was expedited by the engineer (Barton and Logudice) through the New York State Department of Environmental Conservation (NYSDEC) and Army Corp of Engineers to allow for construction in favorable conditions of low water level at the end of summer while avoiding the start of the trout spawning season in October.
OCWA utilized their pipeline contractors (W.D. Malone Trucking & Excavating, Inc. and D.E. Tarolli, Inc.) to perform the work combined with in-house staff to inspect and coordinate repairs of the pipeline. As a matter of precaution each section of exposed pipe had its bell joints unearthed and retrofit clamps applied. The goal is to minimize the risk of a leak at these locations and avoid the need to disturb the repaired stream bank and/or bed in the future. Two sites were completed in 2015 and the other two were completed in 2016. The 2015 sites are growing well and the bank restoration plantings have survived well through the winter and subsequent summer. Adjacent property owners have complimented the work and are very pleased with the combined protecting of the water supply and respecting the value and importance of the creek.
OCWA—Central New York’s Water Authority—was established by act of the New York State Legislature in 1951 and currently serves over 340,000 residents in Onondaga, Oswego, Madison, Cayuga and Oneida counties.OCWA Executive Engineer Andrew Weiss (right) accepts Emergency Project of the Year Award from APWA
The Authority is one of the 100 largest water systems in the country, operating over 2,000 miles of water main, 55 storage facilities and 42 pump stations.