Coliseum Lake – Water Quality Retrofit

Company: i+iconSOUTHEAST
Industry: Water/Wastewater
Location: Hampton, Virginia
Expected Completion Date: May 2, 2016
Project Website

The Coliseum Lake Retrofit project is located on the southeastern part of Virginia, just outside of Virginia Beach. The project is designed to help filter out nitrogen, phosphorus and suspended sediments from entering Newmarket Bay which would eventually flow into the Chesapeake Bay without these environmental measures.

Essentially this project acts as a series of check dams which will filter out any pollutants that make it into the lake. A majority of the runoff is caused by I-64 which runs parallel with the lake. The runoff from the highway, along with the other runoff from the parking lots and fields will be sent into the first holding cell which is held back by a wetland bench. This wetland bench is a half-acre in size with over 520 shrubs, 35 trees and a variety of other wetland plants which were chosen for their ability to filter out nitrogen and phosphorus. Once the water is filled to a certain elevation in the first cell it will filter over the wetland bench and a 10’ rock check dam and it will enter into a second holding cell which is held back by a sheet pile wall that runs across the lake. This sheet pile weir is used to filter out any remaining pollutants that made it through the first cell before it gets into the Chesapeake Bay.

What impact does this project have on America?

The lake was originally a borrow pit for the I-64 highway that runs parallel to the lake. After completion of I-64, the borrow pit was converted into a storm water management lake, with nearly 400 acres of parking lots, fields and roads flowing into the lake. It is no surprise that a lot of these chemicals and sediment are becoming an issue for wildlife and the surrounding ecosystem.

In 2010 the EPA passed a Pollution Reduction Act which mandates all cities surrounding the Chesapeake Bay to reduce their daily pollutants to 60% by 2017. The City of Hampton decided to move aggressively towards the EPA’s goal by starting this project. At the completion of this project, the city will have met 9% of their overall goal set forth by the EPA.

Once the EPA’s goals are met there will be a drastic change to the surrounding ecosystem. Based off the geography of Virginia, the Chesapeake Bay acts as a big drain with all the runoff from roads and farms flowing into the bay. The Bay is a major producer of various types of edible fish and is home to the Blue Crab. Over the years the Bay has lost a tremendous amount of wildlife due to trash and other chemicals that flow from the surrounding cities and into the Bay. Without the fish and wildlife produced by the Chesapeake Bay the economy in the immediate vicinity would dip dramatically. The Bay is roughly 4,500 square miles which serves as a home for many fishermen and tourist a like. The eastern part of Virginia depends heavily on tourists to support the economy and with no wildlife or unclean water there is nothing that will bring these people in.

What interesting obstacles or unusual circumstances did you overcome to complete the project?

When working on projects that deal with storm water runoff it is essential to keep the area you are working in dewatered for the operations at hand. For the duration of the Water Quality Retrofit i+iconSOUTHEAST needed to keep the fore bay area dry in order to support all dredging and dirt work operations. It’s a difficult operation to keep an area dry that was originally designed to support 400 acres of storm water runoff. The fore bay and cell one needed to be pumped down at all times in order to place rip rap as well as install the wetland plants which will eventually serve the purpose of filtering out all pollutants from the runoff. Once all of these activities are complete the fore bay, as well as cell one, will be flooded to start the filtration operation.

Along with keeping these areas pumped down, a new system to this area had been implemented to the sheet pile wall. Because the Lake water is brackish, a cathodic system was implemented much like the ones used on ships to keep the hauls from rusting out. This cathodic system uses a series of anodes welded directly on to the sheet pile wall. There are a total of 76 anodes that are directly welded to the front and back of the sheet pile wall. These 375 lbs anodes are made from high grade zinc which are designed to divert the corrosive electrodes from eating away at the steel sheet pile wall. Instead these anodes will be torn down over time and replaced as needed over the life of the sheet pile wall. These anodes are not easy to install because of the sheer size and weight of them. To install these anodes it required the use of divers to physically weld the anodes to the sheet pile wall. Coordinating between the divers and the crane operator isn’t an easy task. To keep these massive anodes in the correct spot in a tidal lake requires great attention to detail and a spotter who is experienced in giving good commands.

What dangers and risks did you encounter, and describe any extraordinary methods used to keep workers safe?

COMMUNICATION: With this job came some unusual work activities that required full attention and clear communication between the owner, supervisors and workers. This sheet pile wall connects directly into VDOT’s new sheet pile wall which is running perpendicular to the weir being constructed. Because these are two separate contracts, which are being fulfilled in the same time frame, close communication needed to be establish to keep both projects on schedule and under budget.

CONFINED SPACES: With the VDOT sheet pile wall it requires a man to occupy a tight space between the new sheet pile wall and the existing to support the drainage opperation. To combat these risks i+iconSOUTHEAST consulted their safety director to put a plan into action should anything arise while a man is between the two sheet pile walls. The main concern is the tight space will fill with carbon monoxide produced from exhaust fumes from cars driving on I-64. i+iconSOUTHEAST determined the best way to keep our people safe is to have an oxygen sensor at all times down in the confined space with the worker. If the oxygen sensor detects abnormal levels of harmful gasses it is up to the spotter at the top of the highway to pull the worker in the tight area out using a series of pulleys approved by OSHA.

UNDERWATER WELDING: With the constant tidal changes and unusual weather patterns, placing anodes can be very challenging. These 375lbs anodes needed to be welded 5’ below the waters’ surface in order for the system to function correctly. i+iconSOUTHEAST found the safest way to install these zinc anodes is to hire underwater divers. These divers will work closely with the crane operator and spotter who will be holding the anodes in place while the divers weld it to the sheet pile wall. In order for this work to remain safe, constant communication will be established with the use of radios and hand signals to be sure all parties are on the same page when placing these anodes.

How did you leverage new technologies to work faster and reduce waste?

In order to keep the guys in the field more organized i+iconSOUTHEAST furnished iPads for all foremen and superintendents on the job. These iPad’s help keep track of all equipment on their job site as well as total man-hours used to date. This gave an accurate summary of all resources needed to keep the job on time and within budget. The iPads are used mainly to fill out daily planners, organize safety tool box talks, log equipment hours, track man-hours and to review plans and specifications in the field. By utilizing this technology it has helped tremendously with supplying the correct manpower for the different activities at hand. As the man-hours are logged into the iPads, the guys in the field know exactly where they stand with manpower left for the duration of the project. This has made the operation in the field more efficient and easily tracked for future historical data within the company. Thus giving more accurate bids to other owners and stakeholders for future projects.