25. 6” sanitary force main
18” water main
18” storm sewer
Large storm sewer junction box
12” sanitary force main
Another 6” water main
24” storm sewer
Telephone lines
6” water main
Underground power
6” gas main
Fiber optic (Federal)
Overhead power lines
35. Funding
• Phase I – North Interceptor
– Rate increases
– Municipal bonds
• Phase II – North Interceptor
– Clean Water State Revolving Funds (CWSRF)
NDEQ
Today I’m going to talk about the City of Grand Island’s new North Interceptor pipe. Other wise known as $35 M later.
Conceptually the gravity interceptor was proposed in the 70’s, but costs were seen as too prohibitive and a series of lift stations were built instead. In this discussion I will talk mainly about the costs, the challenges, and the benefits of this large scale, conversion to gravity sewer project.
Officially, the planning and design was picked up again in 2010. And here we are today, discussing the completion of The City of GI….[title]The City of Grand Island WWTP serves a population of about 50,000 people. Major industries treated at the plant include facilities such as meat processing, packaged food processing, and manufacturing operations.
Today, we are at substantial completion on what has been a $35 million dollar project. Nearly six (6) miles of large diameter sanitary sewer has been installed. The alignment utilized Capital Ave, the Grand Island utility ditch, Skypark Rd, and Museum Dr. The Grand Total of $35M includes: Phase I, Phase II, engineering and consulting fees, as well as land acquisition fees.
Completed in two (2) major phases this project has increased the overall capacity of the system, and reduced I/I, and wet weather back-ups. Phase I was completed during the summer of 2014.
Due to multiple point breaks and a concern that a point break could occur under the RR crossing, there was an urgency to complete Phase I in order to increase overall capacity within the system avoid more point failures within the system.
Phase II of the project began at l.s #19 and installed 48” sewer to Skypark Rd. Phase II also included the abandonment of six (6) lift stations, with the potential for three (3) more.
As I mentioned lift station #19, which saw about [1 mgd] was abandoned with Phase II. Phase II also abandoned six (6) total lift stations. From west to east, lift stations 15, 8, 2, 10, and 13 have been abandoned under the Phase II contract. Lift stations 4 and 6 may be abandoned when time and budgets
allow.
Outside of lift station #19, the five (5) additional lift station abandonments for Phase II totaled $5.3 M.
The lift station abandonments in the long run are a great benefit to the collection system. Less energy, maintenance, and corrosive H2S is generated.
Overall, The project has replaced a failing pressure system that has historically encountered wet weather back-ups, point breaks infiltration and inflow, and corrosive environments mainly due to the turbulence and activity of lift station #19.
However, the transition is very invasive to the community.
Hello!
During lift station abandonments and connection of these sewer sheds to the new North Interceptor, residents were prevented access to driveways for about sixty (60) days while large segments of streets were removed, and new gravity sewer installed. We also made modifications and or improvements to storm sewer and water services. New paving was placed, and new sidewalks, and portions of driveways were replaced in many sections.
Minimal disruptions to utility services were experienced. We notified homeowners via letters, phone calls, and kept on top of questions by simply being onsite and having a responsible contractor who would knock on doors and keep people informed.
Special provisions were made for the continued services of garbage, recycling, and mail.
Overall, the residents were supportive, positive, and knew from our press releases and media events that the project was eliminating lift stations and simplifying the sanitary sewer collection system.
This past May we experienced a good rain that slowed down paving. The contractor, SJ Louis, was very proactive in drying out the subgrade and keeping residents informed.
Here we are in the beginning stages of Phase II installing pipe on the north side of Capital Ave.
Phase II utilized the Grand Island utility ditch for a large portion of the alignment. The portion of the ditch from Broadwell Ave to the BNSF tracks was a steep dropoff right next a high traffic corridor in Grand Island. This project allowed for portions of this steep ditch to be filled in and for new 60” polypropylene sewer to be placed. Stormwater improvements for this project totaled about $600,000.
Overall, approximately $2,000,000 was spent on street paving, and sidewalk and curb upgrades.
Numerous challenges have been encountered during construction related to groundwater dewatering and discharge, site contamination, utility conflicts, capital improvement project overlap, perceived maintenance challenges, and value engineering considerations.
Groundwater dewatering. Grand Island’s average groundwater level sits about 10 feet below grade. Some people in City limits are still on private water wells. As we installed this 48” diameter sewer at approximately 20 feet below grade in areas that were not connected to City water we began to take a proactive approach and considered the cone of influence
At this point we made appointments with homeowners in order to either lower the well pump or connect them to City water.
In this photo, Shane’s Pump and Windmill service inspects a pump.
We also encountered challenges with dewatering discharge. During dewatering of the large interceptor, the well contractor, Mersino placed wells at a 60 ft. casing depth, placed them along alignment of the pipe every 200 ft., and ran each pump at approximately 1200 gpm. During the 48” pipe installation about 10 wells would run continuously, before moving down the line. The majority of the discharge water was sent either north or east through existing storm water channels. Here the water is shown east of town and flowing northeast along a natural waterway called the Warm Slough. We were in communication with a farmer’s group in this area. We gave this group a timeline of dewatering activity that would impact them. Their biggest concern was winter months in which ice damming can flood & freeze out fields. We monitored the areas here and luckily were able to avoid any major challenges with this group.
Optional: We have a special weir in the junction box here which was monitored to ensure that areas of town dewatered west of this point flowed north.
In conjunction with the 48” sewer installation moving westerly toward lift station #19, the City Public Works Dept. was underway with the Capital Avenue Widening and Stormwater improvement project. So, for a period of time the dewatering discharge could not flow in the normal pattern east along Capital Avenue. And so came to fruition the dewatering discharge re-route.
As I mentioned, the main artery for City stormwater conveyance in the West part of the City is in Capital Avenue. In the part of the town, the entire collection system will eventually drain to Capital Avenue. So there was no where else to put our dewatering discharge water when construction was taking place in this part of town. As the installation moved west toward 281, all dewatering discharge flowed back to this detention pond, where it would normally overflow back to the Capital Avenue stormwater pipe. Since the downstream contractror working on stormwater inlets needed this pipe as dry as possible, the storm sewer outlet was plugged, and the water was instead pumped north through the new re-routed system. The dewatering contractor set up an above ground re-route.
So there were still many layers to the project overlap challenges. The engineers with Olsson Associates were involved with both projects and were able to effectively navigate with Black & Veatch, SJ Louis, and the Capital Avenue Paving Project contractor.
We’ve got:
Unbeknownst during design there used to be a gas station at the SW corner of the Broadwell Capital Intersection. The plan was to perform a trenchless crossing at this intersection and maintain a safe clearance from existing utilities which are numerous.
During the street removal a strong gasoline odor was detected. Findings were submitted to the NDEQ and after much coordination between all parties, it was agreed that SJ Louis could not safely perform the trenchless crossing (due to flammability risks), and that an open cut excavation would be required. [insert sound byte].
During excavations an old, brick, storm water junction box fell apart. We then had to complete the construction of new and improved stormwater junction boxes for this intersection. In addition, due to the risk of contaminated soils and corrosion, specially ordered nitrile fittings were used at this location.
Believe it or not, the change in conditions resulted in a negative change order cost of about $45,000. This includes the extra stormwater work. The change in conditions did cause a delay in the Paving Project. The delay cost that project an extra $100,000.
Believe it or not, the change in conditions resulted in a negative change order cost of about $45,000. This includes the extra stormwater work.
In conjunction with value engineering our engineering team amongst Black & Veatch and Olsson Associates consistently negotiated and navigated through change order items so that the unexpected changes were delivered at a cost that would be acceptable to the overall project and therefore the rate payers within the community.
These cast in place manholes were to be placed in the middle of the utility ditch. SJ Louis was planning to use a 92” fiberglass reinforced manhole (as used all all other portions of the North Interceptor) and incorporate a concrete shell with a base, walls, and deck.) In addition to access concerns, we were concerned about creating potential diving platforms in the utility ditch. (attractive nuisance).
We were able to take another look at this situation and eliminate the costly cast in place manholes by filling in small portions of the ditch; which allowed us to install the standard 92” FRP manholes along with installing extensions of 84-inch CMP (corrugated metal pipe).
The new 84” CMP that I was talking about. even able to install a new 8-inch service district that is able to serve thirteen (13) properties currently on septic tanks within City limits.
Overall, the project began with a negative change order establishing new unit pricing for all pipe materials to be embedded in native material vs. the awarded imported gravel. In the end this credit amounted to over $250,000 [check with Tim]. We still used granular bedding when we encountered a clay layer, but fortunately native sand was able to be used for the majority of the large diameter pipe.
With this credit, we took the opportunity to address as much aged infrastructure as we could and
This map represents areas of town that are not served by City sewer. In general, for our purposes here the green and red areas are areas still on septic tanks. The main idea is that we were able to construct a sewer extension in order to serve this area of town.
North Interceptor Phase I was funded through a series of gradual rate increases and municipal bonds. North Interceptor Phase II has been almost entirely funded by Clean Water State Revolving Funds (CWSRF) made available from the Nebraska Department of Environmental Quality (NDEQ).
The CWSRF interest rate is at least two (2) percentile points less than a municipal bond. Another positive point of the CWSRF funds, is that they have allowed Grand Island to abandon the five (5) lift stations that I mentioned earlier all at once rather than over a more spread out time frame.
The savings in interest rates between SRF and bonds payed for the additional lift station abandonments. North Interceptor Phases II qualified for green funds under the CWSRF guidelines and receives the lowest interest rate possible which is currently at 2.25% due the abandonment of City lift stations and the conversion to gravity sewer.
We’ve reduced our energy footprint.
With the abandonment of 6 lift stations, and with lift station #19 being the largest energy user, we have been able to nearly halve our power consumption with the conversion to gravity sewer.
$35M is inclusive of all costs – including construction, engineering, land acquisition, and all internal costs. The total cost also includes fees for a complete budget analysis and attorney fees for facilitating the loan with NDEQ.
Thanks to everyone’s involvement to date, the overall project remains on schedule and on budget. [show the other slide]
There’s still work to be done. Currently Grand Island troubleshooting methods in order to alleviate contributors to the South Interceptor by reducing I/I and re-routing another lift station from the south to the new north interceptor.
Add more construction photos. Print out summary of pipe length and costs for Phase I and II.
