This historic photo shows one of the many Des Moines streetcars that ran on the Sherman Hill trolley line until 1951.

The lower level of the Green & Mail Pilot Project will be used as a green education center for the public. So significant renovation is taking place in what was the basement of the building. Since the construction crew will have to underpin the entire building, there was a decision made to remove the basement floor and replace it. As part of this process, the entire floor will be lowered to increase the ceiling height, accommodating the comfort of future visitors. However, the elevation of the sewer in the street was already established, and the Green & Main crew needed to tie into the street sewer at a lower level.

Excavation Surprise

Sinkhole resulting from discovered trolley line.

Time to dig up the street!

Prior to digging, all possible existing utilities had been researched via Iowa One Call. (The Iowa One Call notification system is a free call and a free service to anyone planning an excavation in Iowa.) The street was marked to highlight various known lines and the location of the existing sewer. But, not surprisingly, this historic Sherman Hill street had some history to reveal under its layer of asphalt and then layer of brick.

The crew used a diamond saw to cut into the street from the exit of the building to the sewer main under 19^th Street. Suddenly, sparks started flying. Quickly discovered were two old trolley tracks that ran down 19^th Street, along with four wooden rail ties that had provided the frame for the tracks. While digging with an excavator to remove the tracks and rails from the street, the crew also discovered a four-inch cast iron pipe running parallel to the tracks, five feet under the street’s surface.

Des Moines Utilities and Public Works Lend a Hand

The sink hole discovered was the size of a Smart Car!

The construction crew stopped work immediately and made a few calls. Enter Des Moines Public Works, Water Works and Mid-American Energy. As the city crews cautiously investigated the situation, a small sinkhole was discovered under the old trolley line; then an even larger sinkhole emerged about the size of a Smart Car. However, the initial concern remained:  the proper identification of the pipe.

The pipes did not appear on any existing city utilities map. And so to identify the purpose and contents of the pipe, Public Works asked the Green & Main construction crew to drill into the pipe looking for either water or gas. Neither were found, but the pipe did contain some ground water and traces of a petroleum odor. (The electrical lines to run the trolley were typically coated with a tar-like substance to protect the wires). Once deemed safe to proceed, the crew cut and removed the abandoned pipe.

Excavation of street asphalt and brick layer to connect the new plumbing system to the city sewer.

As a precautionary step, Des Moines Public Works scoped the sewer line and discovered that about 25 feet of the existing main sewer line was cracked and had partially collapsed. The sewer line was cleaned and temporarily fixed and the main sewer line will be replaced sometime this year.

Still to be resolved, though, were the sinkholes. A self-leveling grout-type substance filler called K-Crete was pumped into the sinkhole to fill the void, preventing the street from becoming unstable. Public Works crews completed this and the resurfacing of the patched area.

Green & Main Pilot Project Benefits from New Sewer Main

Although this temporary fix resolved some surprise issues under the street’s surface, Green & Main crews won’t be able to connect to the main sewer line for some time as they await Public Works’ permanent repair of the main line. The good news? Since a new sewer main is necessary, when it is in place Public Works will run it directly up to the curb of the Pilot Project building which provides the depth we need to lower the sewer line.

Not only will this provide the needed elevation drop, accommodating the needs of the building, it allows the construction crew to proceed with the installation of the ground work and installation of a subsurface drain within the building. This installation will then allow the crew to reinstall the concrete floor. Much appreciation goes to Public Works’ Jay Bennett, Sewer Operations Manager, and Ron Silvers, Senior Construction Inspector, who worked extensively with the Green & Main crew to develop an ideal solution that would allow them to continue the groundwork inside the building.

The challenge will be that the building will lack the capacity to drain anything into the sewer until the city repairs the sewer and the street. But it’s worth the wait. Pending the completion of the new sewer line, we will continue to work on preparing the building for interior work and its future occupancy.

Street construction barricade around the sinkhole.

– Ann Wilde is a Des Moines marketing strategist and writer who also has a special interest in preserving and creating sustainable communities. She prefers it when plants bloom with minimal human attention.

Chaden Halfhill on the first floor during construction.

Even when your construction crew involves surgeons of the earth, you have to remain ready to deviate from plans to overcome unexpected hurdles. Here is how we overcame one recent hurdle that required an orchestration between our crews and Des Moines City Works Department.

A great man said this to me recently as he leaned out of the cab of his backhoe, “I am a surgeon, just with different tools.”

Ron Gomis invites such a precise comparison because he can shave dirt from an existing foundation with a bucket the size of a wheel barrow better than most guys clean their face with a sharp razor. He’s rather talented with large machinery, supported by an upbeat and dedicated team that moves dirt while he digs.

Excavation of street asphalt and brick layer to connect the new plumbing system to the city sewer.

However, the flow of teamwork can come to a complete standstill when plans unexpectedly change. Of course, construction can certainly deviate from the straight line of theory and Gantt charts, and the last few days have certainly proved this truism.

How We Overcame a Hurdle

The other day, work was progressing as expected. The crew cut away several layers of asphalt, concrete and brick pavers before digging a diagonal trench from the storefront of the Green & Main Pilot Project building towards the center of 19th Street, exposing an initial 15 feet of a 6” sewer line that we needed to lower and relocate. What began as routine resulted in a delightful discovery of steel trolley tracks (read this post outlining details and photos of the trolley track find) that were buried amongst the paving layers. We also located where the cast iron sewer pipe transitioned to the original clay tile four feet to the east of our foundation.

Just short of the municipal sewer we discovered a sinkhole below the surface of the street directly underneath the bus route; the hole was the size of a Smart Car. This discovery initiated several days of meetings with various municipal departments, conversations to determine how to move forward without the ability to establish fall height for our system and tie our drain into the city’s sewer service.

The city sewer had a crack that spanned nearly twenty-five feet long, almost the entire length of our building, with the sinkhole impeding drainage from the top of the hill two blocks north. Using enhanced diagnostics, officials determined the sewer would need to be replaced from Cottage Grove to Center Street, two city blocks. Defining a schedule for such work remained uncertain at best.

In order to continue progress on Green & Main, Jason Anderson, Lead Artisan for Silent Rivers, orchestrated a solution with Des Moines City Works Department that allowed us to relocate the building’s drain to provide the required fall needed to accommodate additional headroom and necessary changes to the plumbing system. This relocation allowed us to position the main drain line access twenty feet south, establishing the new connection well below the foundation and stubbing the drain line into the right-of-way for future integration during the upcoming sewer overhaul.

Whew! After numerous meetings, excellent problem solving and public-private collaboration, we were again marching. Earth surgeon Ron Gomis returned to fill his incision and patch the roadway so that buses could return to 19th Street.

Hurdles are Part of the Process

I cannot help but reflect on the many hurdles we have overcome simply to begin construction, as this project has been anything but linear. From educating the financial community about green building and LEED to restoring abandoned zoning rights, the development of this 5,075 square foot project has required patience, tenacity and a sense of humor, if not a willingness to adapt.

The hurdles began as early as the building’s acquisition. The transaction started as a standard real estate purchase agreement where the buyer met all counter-offer requirements. It quickly regressed into months of positioning on behalf of the sellers and their agents to leverage a higher sale price. The result: a Sheriff’s Sale Deed that when combined with legal fees accrued during the whole debacle cost the same as the original purchase price. Just short of 6 months of wasted time, we finally began the process in earnest.

And now here we are in full-scale construction. The process of overcoming hurdles progresses, and we continue to sharpen our skills as surgeons of sustainability!

– Chaden Halfhill is an entrepreneur and visionary of the Green & Main Initiative. He does not like it when hurdles are above his knees as it is harder to jump over them and the running start is longer.