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Sept. 5 — This section of riverbank on the eastern section of the MichCon property had supported a number of large trees and thick undergrowth, all of which had to be removed to facilitate the remediation work. The site will be planted with more than 200 native trees to compensate for the removal. The stakes in the river indicate the extent of sediment excavation. Once the sediment is excavated and a cap is placed, rounded, glacial stone will be installed to stabilize the bank, which will be planted with bands of native grasses, shrubs, and trees. by DTE Energy

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• Sept. 5 — This section of riverbank on the eastern section of the MichCon property had supported a number of large trees and thick undergrowth, all of which had to be removed to facilitate the remediation work. The site will be planted with more than 200 native trees to compensate for the removal. The stakes in the river indicate the extent of sediment excavation. Once the sediment is excavated and a cap is placed, rounded, glacial stone will be installed to stabilize the bank, which will be planted with bands of native grasses, shrubs, and trees. by DTE Energy /calendar/photologue/photos/MichCon cleanup 2012/cache/MichCon_cleanup2012_001_fullsize.jpg
• Sept. 5 — This section is the western, or upstream, extent of the planned sediment excavation. A silt fence is in place to prevent soil from getting into the river. Concrete barriers can be seen upstream. The barriers deflect water flow around the sediment excavation area. by DTE Energy /calendar/photologue/photos/MichCon cleanup 2012/cache/MichCon_cleanup2012_002_fullsize.jpg
• Sept. 12 — Workers deploy a “turbidity curtain” in the Huron River to isolate the excavation area from the river flow and prevent any migration of turbidity or contamination from entering the river and being carried downstream. by DTE Energy /calendar/photologue/photos/MichCon cleanup 2012/cache/MichCon_cleanup2012_003_fullsize.jpg
• Sept. 12 — Workers prepare to install an oil boom that will be positioned inside of the turbidity curtain. The boom will trap any oils that may rise to the surface during excavation. by DTE Energy /calendar/photologue/photos/MichCon cleanup 2012/cache/MichCon_cleanup2012_004_fullsize.jpg
• Sept. 12 — This onsite wastewater treatment system will pre-treat ground water and surface water that is collected during remediation. The treatment system consists of an oil water separator, bag filter, sand filter, and activated carbon units. The treated wastewater is discharged to the city’s sanitary sewer system in accordance with an approved wastewater discharge permit. by DTE Energy /calendar/photologue/photos/MichCon cleanup 2012/cache/MichCon_cleanup2012_005_fullsize.jpg
• Sept. 12 — Six perimeter air monitoring stations like this one are deployed around the site. They will help ensure the excavation activities do not impact air quality in the area. Particulate matter and organic constituents are monitored in real-time and are compared to predetermined action levels. by DTE Energy /calendar/photologue/photos/MichCon cleanup 2012/cache/MichCon_cleanup2012_006_fullsize.jpg
• Sept. 26 — Workers spray an odor-masking foam on a truckload of soil that is impacted by tarry residuals produced in the manufactured gas process. The residuals have an odor similar to creosote or mothballs. The foam is used for soils being trucked from the site and on open excavations at the end of the work day. While the odor presents no health risk, the foam is used to minimize any impact on site neighbors during the remediation process. by DTE Energy /calendar/photologue/photos/MichCon cleanup 2012/cache/MichCon_cleanup2012_007_fullsize.jpg
• Sept. 26 — A worker fills sandbags that will be used to secure a “turbidity curtain” placed in the Huron River in the area where sediments are being excavated. The turbidity curtain prevent small sediment stirred up during excavation from being carried away from the remediation site by the river current. by DTE Energy /calendar/photologue/photos/MichCon cleanup 2012/cache/MichCon_cleanup2012_008_fullsize.jpg
• Sept. 26 — An excavator removes impacted soil from an area surrounding a concrete foundation that supported a boiler. by DTE Energy /calendar/photologue/photos/MichCon cleanup 2012/cache/MichCon_cleanup2012_009_fullsize.jpg
• Sept. 29 — Dan Wyant (right), director of the Michigan Department of Natural Resources, speaks to guests attending a tour of the remediation project site. by DTE Energy /calendar/photologue/photos/MichCon cleanup 2012/cache/MichCon_cleanup2012_010_fullsize.jpg
• Sept. 29 — Shayne Wiesemann, DTE Energy senior environmental engineer and project manager, used a site schematic to show visitors where the area they are viewing sits in relation to other major features of the site. by DTE Energy /calendar/photologue/photos/MichCon cleanup 2012/cache/MichCon_cleanup2012_011_fullsize.jpg
• Sept. 29 – Shayne Wiesemann, DTE Energy senior environmental engineer and project manager, tells participants on a site tour about one of the six monitors on site that continuously monitor air quality. The monitors have not detected any adverse air quality conditions. by DTE Energy /calendar/photologue/photos/MichCon cleanup 2012/cache/MichCon_cleanup2012_012_fullsize.jpg
• Oct. 10 — A dozer grades a near-shore area with clean fill soil. by DTE Energy /calendar/photologue/photos/MichCon cleanup 2012/cache/MichCon_cleanup2012_013_fullsize.jpg
• Oct. 10 — A temporary silt fence separates the shoreline area, which is covered with smooth river stone, from the soil used to re-grade and cover the near-shore area. The soil will be planted with native grasses, shrubs and trees. by DTE Energy /calendar/photologue/photos/MichCon cleanup 2012/cache/MichCon_cleanup2012_014_fullsize.jpg
• Oct. 10 — In an excavated area along the river, a power shovel drives a fencepost into the soil. The fencepost will be used to anchor one end of a turbidity curtain, which will prevent lightweight sediments from being carried downstream during excavation activities. by DTE Energy /calendar/photologue/photos/MichCon cleanup 2012/cache/MichCon_cleanup2012_015_fullsize.jpg
• Oct. 10 — Workers install additional turbidity controls downstream from an area of sediment excavation. by DTE Energy /calendar/photologue/photos/MichCon cleanup 2012/cache/MichCon_cleanup2012_016_fullsize.jpg
• Oct. 10 — Sheet piling provides stability for a shoreline excavation area that will require deeper excavation (10 to 12 feet) than other shoreline areas. Most shoreline excavtion depths are about 3 to 5 feet and the piling is not needed. by DTE Energy /calendar/photologue/photos/MichCon cleanup 2012/cache/MichCon_cleanup2012_017_fullsize.jpg
• Oct. 10 — Excavation of a near-shore section of the site exposes a building foundation (left). by DTE Energy /calendar/photologue/photos/MichCon cleanup 2012/cache/MichCon_cleanup2012_018_fullsize.jpg
• Oct. 18 — A dozer contours clean fill soil in a near-shore area where excavation is complete. by DTE Energy /calendar/photologue/photos/MichCon cleanup 2012/cache/MichCon_cleanup2012_019_fullsize.jpg
• Oct. 24 — A pipe protrudes from the stone covering a completed area of excavation. The pipe is part of a system designed to allow monitoring and removal of any MGP residuals that might move through the soils from the upland portion of the site. Any oils or other byproducts will be captured in the engineered collection system and removed for proper disposal. by DTE Energy /calendar/photologue/photos/MichCon cleanup 2012/cache/MichCon_cleanup2012_020_fullsize.jpg
• Oct. 24 — Clean fill is delivered to the site to provide cover and allow for proper grading of excavated areas. by DTE Energy /calendar/photologue/photos/MichCon cleanup 2012/cache/MichCon_cleanup2012_021_fullsize.jpg
• Oct. 24 — A view of the remediation activity from the opposite bank of the river. by DTE Energy /calendar/photologue/photos/MichCon cleanup 2012/cache/MichCon_cleanup2012_022_fullsize.jpg
• Oct. 24 — Restoration of the riverbank using large glacial stones, as seen from the opposite back of the river. by DTE Energy /calendar/photologue/photos/MichCon cleanup 2012/cache/MichCon_cleanup2012_023_fullsize.jpg
• Oct. 31 — MichCon's Broadway Station site remediation. by DTE Energy /calendar/photologue/photos/MichCon cleanup 2012/cache/MichCon_cleanup2012_024_fullsize.jpg
• Oct. 31 — Large glacial stones cover a section of the shoreline where excavation is complete and restoration activity is under way. by DTE Energy /calendar/photologue/photos/MichCon cleanup 2012/cache/MichCon_cleanup2012_025_fullsize.jpg
• Oct. 31 — Excavation of impacted soils and sediment continues in an area downstream of completed sections. by DTE Energy /calendar/photologue/photos/MichCon cleanup 2012/cache/MichCon_cleanup2012_026_fullsize.jpg
• Oct. 31 — Piping discovered and removed during excavation is stockpiled on a section of a tiled floor from the MichCon service center building, which was deconstructed in 2010. by DTE Energy /calendar/photologue/photos/MichCon cleanup 2012/cache/MichCon_cleanup2012_027_fullsize.jpg
• Nov. 21 — The yellow float of a turbidity curtain, used to minimize sediment from the work area entering the river flow, marks the final section of shoreline remediation near the Broadway bridge. by DTE Energy /calendar/photologue/photos/MichCon cleanup 2012/cache/MichCon_cleanup2012_028_fullsize.jpg
• Nov. 21 — Cap placement along the shoreline across from the outfall of the Argo Dam millrace is being completed following the removal of impacted soil and sediment. Larger stone will be placed along the water’s edge to complete the shoreline restoration. by DTE Energy /calendar/photologue/photos/MichCon cleanup 2012/cache/MichCon_cleanup2012_029_fullsize.jpg
• Nov. 21 — Workers prepare to install piping for a monitoring well that permits testing of groundwater captured by an impervious layer of clay underneath the sand and stone fill along the riverbank. If necessary, the wells also will allow impacted groundwater to be removed or treated. by DTE Energy /calendar/photologue/photos/MichCon cleanup 2012/cache/MichCon_cleanup2012_030_fullsize.jpg
• Nov. 21 — This section of shoreline shows the combination of materials used to provide final cap and cover for the restored riverbank. Egg-sized stone covers an impervious layer of clay that will prevent any potential migration of impacted groundwater to the river. Along the water’s edge, larger rocks cover the smaller stone to provide stability and a favorable habitat for fish and aquatic insects. A temporary concrete barrier in the river will be removed and the area will be restored with topsoil and native grasses, shrubs, and trees. by DTE Energy /calendar/photologue/photos/MichCon cleanup 2012/cache/MichCon_cleanup2012_031_fullsize.jpg
• Nov. 21 — A pipe for a monitoring well rises from the stone fill material along the riverbank. by DTE Energy /calendar/photologue/photos/MichCon cleanup 2012/cache/MichCon_cleanup2012_032_fullsize.jpg
• Nov. 21 — A mix of native pines and deciduous trees are planted as part of the site restoration plan. The plan calls for planting more than 200 native trees, along with bands of native shrubs and sedges and grasses along the river. Restoration work is expected to be complete in the spring. Originally, that work was to be completed this fall, but the volume of soil and sediment requiring excavation is greater than originally anticipated, so that schedule has been delayed. by DTE Energy /calendar/photologue/photos/MichCon cleanup 2012/cache/MichCon_cleanup2012_033_fullsize.jpg
• Dec. 5 — Reconstruction of the final section of shoreline remediation, just upstream of the Broadway bridge, nears completion. by DTE Energy /calendar/photologue/photos/MichCon cleanup 2012/cache/MichCon_cleanup2012_034_fullsize.jpg
• Dec. 5 — The transition between the completed shoreline restoration and the work in progress shows clearly in this section of shoreline. In the foreground, gravel covers an impervious clay cap. A pipe for a monitoring well also is seen. In the background, the gravel has been covered with clean soil, which has been seeded with native grasses and sedges. Natural fiber mats cover the soil and seed to protect against erosion until the vegetation is established. Rip rap of large stones is in place along the water’s edge to stabilize and the shoreline and provide habitat for aquatic plants and wildlife. by DTE Energy /calendar/photologue/photos/MichCon cleanup 2012/cache/MichCon_cleanup2012_035_fullsize.jpg
• Dec. 5 — Gravel covers and protects an impervious clay cap installed along the shoreline. The gravel will be covered with clean soil, which will be planted with native grasses and sedges. by DTE Energy /calendar/photologue/photos/MichCon cleanup 2012/cache/MichCon_cleanup2012_036_fullsize.jpg
• Dec. 5 — A section of shoreline with excavation, cap construction complete awaits final cover, grading and planting. by DTE Energy /calendar/photologue/photos/MichCon cleanup 2012/cache/MichCon_cleanup2012_037_fullsize.jpg

DTE Energy is calling a major environmental cleanup at the old MichCon site along the Huron River a huge success after more than four months of work.

The bulk of the project is complete now, and DTE has vowed to enter into close talks with the city of Ann Arbor about the future use of part of the site as a riverfront park.

"We hope to make the 14-acre site available for development, public use or both sometime in the near future," said Shayne Wiesemann, a DTE engineer overseeing the project.

Wiesemann said DTE will continue to work with the city, Huron River Watershed Council and other community stakeholders to determine the proper final end use for the site.

"If all the stars align perfectly, we are likely looking at a year or two before any redevelopment work begins," he said. "There may be additional remediation work required onsite, based on the proposed final end use, but that work would likely be performed during site preparation activities."

In this photo from Nov. 21, cap placement along the Huron River shoreline across from the outfall of the Argo Dam millrace is being completed following the removal of impacted soil and sediment. Larger stone was later placed along the water's edge to complete the shoreline restoration.

Courtesy of DTE Energy

MichCon has been a subsidiary of DTE since 2001. It ran a manufactured gas plant along the south bank of the Huron River decades ago and left the site polluted — a problem DTE inherited and has been working cooperatively with the Michigan Department of Environmental Quality to address.

The recent remediation work was done by Terra Contracting with oversight by TRC Engineers, MichCon, the city of Ann Arbor and the DEQ.

Just before Christmas, crews completed excavation of more than 47,000 tons of impacted material from the site, backfilling, capping along the shoreline, and the bulk of the restoration work.

Because the scope of the project was increased (27 percent more material was excavated than originally planned), some shrub and tree planting along the eastern shore will be finished in the spring, Wiesemann said, suggesting the site should look a little nicer and greener once spring has come and the grass and trees are nicely vegetated.

DTE closely coordinated the cleanup efforts with the city's parks and recreation department and the Argo canoe livery to make sure the work had a minimal impact on livery operations, the Border-to-Border Trail and other recreational uses within the area.

"As we planned and discussed at multiple public meetings, MichCon and Terra paid very close attention to the project traffic, odor, dust and surface water controls to ensure the project did not cause any nuisance issues within the city," Wiesemann said.

Mayor John Hieftje said he looks forward to seeing the results of DTE's efforts. He said it's been a general goal of the city for decades to acquire more riverfront land for park use.

"I'm very happy to see the cleanup has made progress," Hieftje said. "When you're talking about property becoming parkland, it has to be cleaned up to a specific standard, and I haven't seen any of that data yet. It needs to be cleaned up to a very high level."

Hieftje said the city doesn't want to assume any liability for future environmental cleanup work. As for how the transfer of the land from DTE to the city might occur in the future, Hieftje said, that's yet to be determined, and the ball is largely in DTE's court at this point.

A map of the MichCon site on display at a meeting last April, showing the areas along the Huron River where DTE Energy planned to conduct an environmental cleanup. The remediation work done along the river's edge didn't address contamination elsewhere on the property.

That means, for instance, the area being cleaned up could be considered safe to use as a public park.

DEQ District Supervisor Mitch Adelman said it seems DTE has hit its mark and the DEQ is pleased to see the pollutants removed from the environment according to plan.

"It looks pretty good out there, from what we've seen," he said. "We look at it as a good next step in terms of bringing (the overall property) to closure."

The remediation work done along the river's edge didn't address contamination elsewhere on the property. For instance, there are cyanide-contaminated soils on the western portion of the property that haven't been cleaned up, Adelman said, noting that's a situation that both MichCon and the DEQ are aware of and it might require additional cleanup depending on the future use of that area.

While it appears DTE has cleaned up the portion along the river's edge to the point where there essentially are no more restrictions on it, Adelman said, DTE/MichCon still will be responsible for continuing to monitor and maintain the impermeable cap it put in place along the shoreline.

Wiesemann said MichCon ultimately is liable for remediating the remainder of the site to an "industrial" or "non-residential" cleanup level consistent with its use and zoning. He said that additional work likely will be performed during the redevelopment phase to take advantage of project synergies.

"However, if potential future developers or owners plan to change the property use to 'residential' or would like to construct a park, they will need to fund the additional cleanup that may be required in order for the property to meet the more stringent cleanup standards," he said.

Ryan J. Stanton covers government and politics for AnnArbor.com. Reach him at ryanstanton@annarbor.com or 734-623-2529. You also can follow him on Twitter or subscribe to AnnArbor.com's email newsletters.