Nine Mile Sanitary Sewer

A combination of factors led to the issues impacting Garfield Lake. We are not denying the dewatering efforts for the Nine Mile Sewer project played a role, but we also must acknowledge the state of Michigan is in a moderate drought. This was not something we could have predicted as the lake is roughly a mile away from the project, while a pond next to the project hasn't gone down.

We are currently diverting some of the dewatering discharge toward Garfield Lake and will continue to do so throughout the project. The lake is connected to the ground water and thus impacted by the lack of precipitation we have received over the last two years.

There is no "quick fix" to restoring the water levels in Garfield Lake. We have enlisted the help of an ecologist to help us better understand the impact and will continue to research best practices for a remedy to the drop in water levels.

The City staff team will be replacing the current pump with a different one in new location in hopes of increasing the output. While we are not sure the impact this will have on the water level of the lake, we are optimistic it may help. We anticipate having it operational within a week or two.
 

Nine Mile Sewer Environmental Final Report

July 15, 2021 - Paragon Laboratories Water Report

Nine Mile Sewer Environmental Final Report

Nine Mile Sewer Dewatering Discharge Sample Results

June 9, 2021 - Paragon Laboratories Water Report

TO:  JEFFREY HERCZEG, DIRECTOR OF PUBLIC WORKS
FROM:  BEN CROY, CITY ENGINEER
SUBJECT:  NINE MILE SANITARY SEWER PROJECT UPDATE
DATE:  FEBRUARY 12, 2021

The Nine Mile Sanitary Sewer project involves the replacement of approximately 6,400 feet of force main sanitary sewer with gravity sewer from Evergreen Court to Kensington. The project is approximately 88% complete, with 5,600 feet of sewer installed (800 feet remaining). Deep construction and the high-water table have made the project challenging and resulted in cost overages and delays.

Most recently, drilling operations were delayed by boulder obstructions which required new bits and additional equipment fabrications by the contractor. Currently, the new method has been successful enabling progress to continue, even if additional rock obstructions are encountered. The delays associated with the rock, the on-going dewatering effort (and diversions), and the other construction modifications have caused the project to continue well beyond the originally anticipated completion date. As expected, the additional effort during this time has resulted in additional costs incurred by the contractor (DVM).

DVM submitted a final claim in the amount of $661,393 to cover the operation and maintenance of the dewatering system through the end of 2020, which staff anticipated when the last change order was requested in November of 2020. The existing dewatering system costs $72,963 per month, along with the ongoing $12,250 monthly cost to divert water to Garfield Lake. An additional $67,248 cost is associated with the sheet piles used to construct the caissons (pits) for the drilling operations.

All of the above requested items result in a total claim of $984,280 to cover operations through March 2021. However, there is approximately $260,000 worth of items in the original contract that are expected to be credited, reducing the current net change to the contract to $724,280. Furthermore, there is $183,000 of unencumbered funds for any future contract changes that arise, or if unused, will reduce the overall impact to the final project budget.  Based on the current status and success managing the rock obstructions, staff expects this change order to cover the remainder of the major project expenses through to the end of construction.

This change order will be on the February 22, 2021 City Council Meeting agenda for consideration. Based on the current status and conditions, we estimate the project could be substantially complete in the next two to four months.

TO:  PETE AUGER, CITY MANAGER
FROM:  JEFFREY HERCZEG, DIRECTOR OF PUBLIC WORKS
SUBJECT:  NINE MILE SEWER PROJECT UPDATE
DATE:  NOVEMBER 12, 2020

The Nine Mile Sanitary Sewer project involves the replacement of approximately 6,200 feet of force main sanitary sewer with gravity sewer from Evergreen Court to Kensington. The project is currently 80% complete, having completed 5,000 feet of sewer installation. The purpose of this project is to provide redundancy to the Park Place pump station, which is 1.6 miles from the closest gravity outlet (near Kensington). The project has taken considerably more effort than originally anticipated primarily due to the following construction related issues:

• Intensive dewatering that has been required to allow for safe construction.
• Diversion pumping to surrounding wetlands to address effects of dewatering.
• New pipe installation technology used to avoid open cutting and prevent tree removal.
• Gravel and rock sub grade obstructions impeding the boring process.

Staff expected this project to be complicated, as most sewer installations of this magnitude are far from routine (especially at depths to 30’). However, it became clear in late 2019 the challenges were going to result in a significant cost increase due to circumstances out of the control of the contractor. A series of update memos from January, April, and September of 2020 are included in this packet to establish a timeline and explain the challenges over the last year.

Staff, OHM, and the contractor have been working to keep the project progressing and have administered change orders for validated items (materials and labor for increased dewatering and diversion pumping). The executed change orders (listed below) have brought the project from the awarded contract amount of $5.8M (bids ranged from $5,8M to $8.7M) to the current $6.7M amount.

Change Order No.	Date Approved	Amount	Description of Change Order
1	4/15/2019	$20.00;	Balancing of Tree Clearing Items No. 7 & 8
2	7/8/2019	-$11.32	Xypex Treatment additive and balancing of Erosion Control – Silt Fence item
3	1/10/2020	$99,000.00	Upsize the dewatering header pipe from 12-inch to 18-inch, material only
4	2/24/2020	$97,332.34	Additional increases for dewatering header pipe and increases for crew days on Basin “B” Improvements and CMP installation
5	5/4/2020	$536,429.91	Increase Item No. 7 (Tree Removal, 6” - 18”) and Item No. 82 (Emergency Excavation) and addition of dewatering claims from the contractor for additional effort, rental equipment, pumps, drop pipes, etc. along with the correlated inspection crew days and contract time.
6	7/13/2020	$81,712.51	Materials for larger 18” dewatering header from MH5 to MH1
7	9/14/2020	$74,250.00	Additional effort to install piping to divert water to Garfield Lake and operate system for three months.

The progress is now again delayed by rock obstructing the pilot bore and preventing pipe installation. The contractor provided an alternative specialized boring head (Mincon rock hammer) to fracture and penetrate through the rock for an additional cost of $250,000. The other alternative would involve excavating (open cutting) and removing the latest obstruction. Excavating to that depth is hazardous and would result in at least 40 additional tree removals and a lengthy full road closure. Therefore, staff recommends use of the rock hammer boring head, and will bring the accompanying change order forward to the City Council meeting on November 26, 2020.

The alternative boring head method will again extend the timeline for completion which now is estimated to be in spring of 2021. Furthermore, another change order will be forthcoming near the end of construction to cover the additional effort discussed herein and the ongoing contractor efforts since late 2019. In order to determine the estimated total project cost, a comprehensive submittal from the contractor will again be analyzed by staff and OHM and will likely require more detailed negotiation before finalizing.  However, staff estimates the total project cost could be similar to the high bid originally submitted (~$9M).

The long-term benefits from replacement of the force main with new gravity sewer still outweigh the additional costs, as it provides 100-year gravity sewer infrastructure with the following benefits:

• Allows for reasonable mitigation of any major failure of the Park Place pump station.
• Eliminates sanitary pump stations to support future development in the area (e.g. Terra), as pump stations present the highest risk of failure.
• Eliminates long-term pump station maintenance (significant staff time and effort, pumps and equipment replacements, utility costs).
• Eliminates need for parallel force main redundancy.
• Allows Nine Mile residents connections to the sewer without the need to maintain a private grinder pump station at their residence.
• Mitigate failing septic systems in the area.
• Allows for the protection of hundreds of trees, as well as vegetative screening for residents on Nine Mile.

Fortunately, the City of Novi has been fiscally responsible and has established a water and sewer fund that allows management of projects that experience unforeseen challenges.  Staff and OHM continue to supervise the contractor’s operations and claims for delays and construction challenges. Staff continues to work toward solutions to keep costs as reasonable as possible and will update City Council on the project as information becomes available.

TO:  PETE AUGER, CITY MANAGER
FROM:  JEFFREY HERCZEG, DIRECTOR OF PUBLIC WORKS
SUBJECT:  GARFIELD LAKE DIVERSION PUMPING
DATE:  SEPTEMBER 4, 2020

The Nine Mile Sanitary Sewer project which replaces approximately 6,200 feet of force main sanitary sewer with gravity sewer from Evergreen Court to Kensington, has taken longer than anticipated and provided several challenges. Extreme dewatering in order to construct the project has potentially caused a negative impact to the surrounding area, including the water level in Garfield Lake.

After several residents reported a receding lake level, staff investigated options to return water back into the lake and surrounding wetlands. Since the dewatering for the project was routed towards the new Terra subdivision detention basin, the simplest and most cost effective solution to get water back to Garfield Lake, was to pump from the Terra basin south down Garfield Road. In late June, a temporary 6” pipe line was installed through the ditch line with an outlet in Garfield Lake (see attached map). Staff cooperated with residents to find an appropriate route for the piping along Garfield Road and over to Garfield Lake. One of the residents installed a “gauge” on his dock that has allowed staff to closely monitor the lake levels (see below pictures).

The redirection pumping has been in operation for over two months and instantly made an impact on the water level (raised 2.5 feet). The level has been closely monitored after the initial rise and has fell around 0.5 feet. Over the past month, it has remained relatively constant (2 feet higher). According to an Ecologist on OHM Advisors staff, the lake level is approximately 1.5 feet below the “normal annual low” water level.

Staff will be bringing a change order to the September 14 City Council Meeting to cover the costs for the setup, pumps, and fuel associated with the three months of temporary diversion pumping. To date, the costs are approximately $70K. Since the water level is fluctuating and the project still has several months of construction remaining, staff recommends continuing the diversion pumping for the duration of the project. Additional costs are ~$13K/month and can be included in a balancing change order with other items when the project is closer to completion.

Furthermore, staff recommends leaving one or two of the dewatering shafts and the temporary pipe in place after the project is complete. This will provide a security measure to pump more into the impacted lake and surrounding wetlands if necessary.

Based on current progress, the installation of the sanitary sewer main is anticipated to be substantially complete by November. The contractor is currently constructing the deepest portion of the project. Staff is optimistic that good progress will be made over the next few months, provided no further subsurface obstructions are encountered.

 

Piping along Garfield Road	Piping along resident’s yard	Water Level “gauge “

 

Pump used to direct water	Discharge point

TO:  JEFFREY HERCZEG, DIRECTOR OF PUBLIC WORKS
FROM:  BEN CROY, CITY ENGINEER
SUBJECT:  NINE MILE SANITARY SEWER PROJECT UPDATE
DATE:  MAY 15, 2020

The Nine Mile Sanitary Sewer project involves the replacement of approximately 6,200 feet of force main sanitary sewer with gravity sewer from Evergreen Court to Kensington. This project has required a significant amount of dewatering to facilitate construction. On May 4, 2020 staff was notified and responded to a concern about the receding water level of a pond (aka Garfield Lake) west of Garfield Road at Deer Run (see attached map). Although the cause is uncertain, there is potential this drawdown is related to the dewatering for the sewer installation. This seems unlikely given the pond is 0.6 miles away from the project activity; regardless, staff has initiated an investigation for potential solutions.

Staff has been in contact with multiple residents in the area, and continues to be available to anyone looking for additional information. Furthermore, OHM Advisors, the engineering consultant who is performing the construction engineering and inspection on the project, has started an assessment of the pond and surrounding wetlands. OHM’s staff Ecologist visited the area last week to gather some initial data, and will continue a monitoring program over the next several seasons as appropriate. In addition, the geotechnical engineering consultant for this project, TEC, and the City’s wetland consultant, ECT, have also been engaged to provide technical expertise.

City staff has contacted the Michigan Department of Environment, Great Lakes and Energy (EGLE), who issued the permits for the sewer installation and the associated dewatering. EGLE has indicated the City is in compliance with these permits, and they will work with staff to coordinate any potential solutions to help reverse the lowering pond elevations.

Two of the preliminary solutions being investigated are summarized below:
 

• Reroute Dewatering Discharge – It may be possible to re-rout some of the existing dewatering discharge to directly into the pond. This would involve the installation of approximately 2,200 feet of above-ground pipe to convey the water to the pond.  Additional survey will be necessary before this option can be pursued further.
• Installation of Augmentation Well – The installation of a temporary well on nearby City property to be used to pump water to the pond may be a viable solution. The depth of the well along with the size of the pump will need to be determined before this option can be pursued further. The well would need to be deep enough to avoid exacerbating the existing issue being observed, but not is expected to be unreasonably deep.

Both of the above options would require a temporary easement from one of the residents adjacent to the pond.

A few of the residents in the area have indicated there is interest in attending an upcoming City Council meeting to express their concern. Staff has advised them how to participate in a virtual meeting should they decide to attend a meeting prior to a return to normal operations.

Below is a summary of the current status of this project (see attached map):
 

• 100% of the 2,850 feet of the open-cut (Traditional Trench Excavation) – this portion of the project is complete. This is the western half of the project which is the shallower portion of the pipe installation.
• 40% of the 3,500 feet of the trenchless (Guided Pilot Tube) - this is the deeper, eastern half of the project. This trenchless method allows for reduced impact to the road, natural features, and residential properties.

Staff is encouraged the project can proceed at a pace closer to originally anticipated moving forward. Based on the current status and conditions, we estimate the project could be substantially complete by the end of October, with final restoration in the spring 2021.