09-18-2007 City Council Study Session PacketCity of Grand Island
Tuesday, September 18, 2007
Study Session Packet
City Council:Mayor:
Margaret Hornady
City Administrator:
Jeff Pederson
City Clerk:
RaNae Edwards
T
u
7:00:00 PM
Council Chambers - City Hall
100 East First Street
Tom Brown
Larry Carney
John Gericke
Peg Gilbert
Joyce Haase
Robert Meyer
Mitchell Nickerson
Bob Niemann
Fred Whitesides
Jose Zapata
Call to Order
City of Grand Island City Council
A - SUBMITTAL OF REQUESTS FOR FUTURE ITEMS
Individuals who have appropriate items for City Council consideration should complete the Request for Future Agenda
Items form located at the Information Booth. If the issue can be handled administratively without Council action,
notification will be provided. If the item is scheduled for a meeting or study session, notification of the date will be given.
B - RESERVE TIME TO SPEAK ON AGENDA ITEMS
This is an opportunity for individuals wishing to provide input on any of tonight's agenda items to reserve time to speak.
Please come forward, state your name and address, and the Agenda topic on which you will be speaking.
MAYOR COMMUNICATION
This is an opportunity for the Mayor to comment on current events, activities, and issues of interest to the community.
Call to Order
Pledge of Allegiance
Roll Call
Invocation - Pastor Gary Schulte, Evangelical Free Church, 2609 South Blaine Street
This is an open meeting of the Grand Island City Council. The City of Grand Island abides by the Open Meetings Act
in conducting business. A copy of the Open Meetings Act is displayed in the back of this room as required by state
law.
The City Council may vote to go into Closed Session on any agenda item as allowed by state law.
City of Grand Island City Council
Item -1
Groundwater Removal Study and Computer Model Presentation
Tuesday, September 18, 2007
Study Session
City of Grand Island
Staff Contact: Gary R. Mader;Steve Riehle
City of Grand Island City Council
Council Agenda Memo
From: Gary R. Mader, Utilities Director
Meeting: September 18, 2007
Subject: Groundwater Removal Study and Computer Model
Presentation
Item #’s: Special Item #1
Presenter(s): Gary R. Mader, Utilities Director
Background
The Aquifer underlying the City of Grand Island is relatively shallow and very porous,
and responds rapidly to surface precipitation. Prior to 2006, the region experienced an
extended drought, but beginning in 2006, normal and above normal precipitation returned
to the area. And with the recent return of heavy precipitation, groundwater levels have
risen several feet, resulting in water intrusion into many basements in the City.
The issue of high water tables and water intrusion into basements has a long history in
Grand Island and the City has undertaken a number of studies to create systems to
address the problem. The more affected areas are in the south in the Park-View, Lamar,
Phoenix, and Circle Drive areas, in the west, some portions of Capital Heights, and on the
east and southeast, the Pleasant View and Seedling Mile areas.
In 1993, a period of wet weather, the Public Works Department designed a dewatering
system to address issues in the Capital Heights area. The design included 17 wells at 500
gallons per minute, with an estimated project construction cost of $1,100,000 (1993
dollars). Most of the cost was associated with the construction of the discharge piping
and the need to remove and replace streets, driveways, sidewalks, etc., in order to
accomplish the pipe installation. The computed cost to the participating home owners
was $1,128 per half acre lot, plus continuing operating costs. Subsurface Drainage
District #1 was created by the Council. It was protested out by a margin of 3 to 1.
Prior to the 1993 district, the issue was also discussed in 1987, during another wet period.
At that time, the City designed two districts, but neither was actually created because of
protest from property owners who would have been included in the district.
In 1994, the City undertook a comprehensive study of historic groundwater levels and
found that except for the older part of town that was built on the “high” ground, nearly all
areas of the town perimeter are susceptible to basement flooding. And those areas are wet
again this year after seven years of drought. That study resulted in City Building Codes
being amended to include a requirement for the installation of collector systems and
sump pumps under all new homes built.
In 2002, the City entered into a joint project with the Central Platte Natural Resources
District (CPNRD) to again address the issue of high groundwater. This was a
comprehensive approach addressing the more problematic areas in the west, south and
east. Olsson Associates was commissioned to prepare detailed hydrologic models and,
using those models, design a comprehensive dewatering system to address the problem.
The system consisted of 25 to 30 wells with discharge piping to remove the high
groundwater to area drainage. There was some discussion of limitations on the drainage
due to concerns with downstream flooding being aggravated by the added water from the
City. The estimated construction cost for that project was $13,063,000 with annual
operating costs estimated at $341,000. The approach at the time was to create a municipal
enterprise fund similar to the water and sewer utilities. The year 2002 was a very dry year
and one of the first in the extended drought from which we have only recently recovered.
The creation of Subsurface Drainage Districts did not result from the 2002 project.
Discussion
In the evaluation of options to address the problems associated with high ground water
levels, a good deal of the hydrologic, computer modeling and engineering work was done
for the 2002 study. In July, City Council authorized Olsson and Associates to update the
2002 model for presentation at a Study Session. That presentation is scheduled for the
September 18 meeting.
Conclusion
This item is presented to the City Council in a Study Session to allow for any questions to
be answered and to create a greater understanding of the issue at hand.
Key IssuesKey Issues• Wet Basements• Sanitary Sewer Infiltration and Residential Pumping to Sanitary Sewer• Property Values• Future Growth in Grand Island• Discharge Location Options• Wet Basements• Sanitary Sewer Infiltration and Residential Pumping to Sanitary Sewer• Property Values• Future Growth in Grand Island• Discharge Location Options
Groundwater Dewatering OptionsGroundwater Dewatering Options• Deep/High Capacity Wells• Shallow/Low Capacity Wells• Horizontal Wells• French Drain• Deep/High Capacity Wells• Shallow/Low Capacity Wells• Horizontal Wells• French Drain
Modeling ObjectivesModeling Objectives• Simulate existing water table conditions• Evaluate aquifer response to pumping• Examine affects of pumping on contamination• Examine affects of pumping and water disposal on existing surface water bodies• Assess potential subsidence due to dewatering• Simulate existing water table conditions• Evaluate aquifer response to pumping• Examine affects of pumping on contamination• Examine affects of pumping and water disposal on existing surface water bodies• Assess potential subsidence due to dewatering
Modeling AspectsModeling Aspects• Utilized GMS – MODFLOW, MODPATH, AND MT3DMS• Utilized GMS’s capabilities for data evaluation and exhibits• Large data base for model• Modeled worse-case scenarios including high and low water tables• Utilized GMS – MODFLOW, MODPATH, AND MT3DMS• Utilized GMS’s capabilities for data evaluation and exhibits• Large data base for model• Modeled worse-case scenarios including high and low water tables
Conveyance/Disposal OptionsConveyance/Disposal Options• Discharge of the water into the Wood River Diversion Channel just south of Stuhr Museum• Discharge of the water into the Platte River where it crosses Shady Bend Road• Discharge of the water into the Platte River south of the Stuhr Museum, and using the water for downstream industrial or other uses.• Discharge of the water into the Wood River Diversion Channel just south of Stuhr Museum• Discharge of the water into the Platte River where it crosses Shady Bend Road• Discharge of the water into the Platte River south of the Stuhr Museum, and using the water for downstream industrial or other uses.
Modeling SummaryModeling Summary• Combination of low- and high-capacity wells meets project objectives• System would consist of eleven 500 gpm wells in NW and seventeen 300 gpm wells and one 1100 gpm in SE• Maximum capacity is 11,700 gpm or 16,85 mgd• Subsidence should not be an issue• Discharge would need to be piped to the Platte River• Surface water impacts are unlikely• Combination of low- and high-capacity wells meets project objectives• System would consist of eleven 500 gpm wells in NW and seventeen 300 gpm wells and one 1100 gpm in SE• Maximum capacity is 11,700 gpm or 16,85 mgd• Subsidence should not be an issue• Discharge would need to be piped to the Platte River• Surface water impacts are unlikely
Opinion of Probable CostsOpinion of Probable Costs$1,042,558$1,048,095$797,826Annual Costs (20 years, 5%, A/P)$12,993,000$13,062,000$9,943,000TOTAL Project Costs90,00090,00090,000ROW Acquisition1,269,0001,276,000969,000Overhead, Legal, Fiscal, Engr.1,058,0001,063,000808,000Contingency$10,576,000$10,633,000$8,076,000Construction Cost Subtotal510,000510,000510,000Control System1,013,0001,013,0001,013,000Dewatering Wells125,000175,000125,000Utility conflicts$8,928,000$8,935,000$6,428,000Transmission LineAlternative #3Alternative #2Alternative #1 ItemPreliminary Opinion of Probable Costs in 2000
Opinion of Probable CostsOpinion of Probable CostsConstruction Cost Index of 1.71 was calculated by the Bureau of Labor Statistics for the same period* Construction Cost Index of 1.79 was used based on FHWA $1,866,463$1,876,412$1,428,432Annual Costs (20 years, 5%, A/P)$23,261,000$23,385,000$17,802,000TOTAL Project Costs165,000165,000165,000ROW Acquisition2,272,0002,284,0001,735,000Overhead, Legal, Fiscal, Engr.1,893,0001,903,0001,446,000Contingency$18,931,000$19,033,000$14,456,000Construction Cost Subtotal913,000913,000913,000Control System1,813,0001,813,0001,813,000Dewatering Wells224,000313,000224,000Utility conflicts$15,981,000$15,994,000$11,506,000Transmission LineAlternative #3Alternative #2Alternative #1 ItemPreliminary Opinion of Probable Costs in 2007*
Opinion of Probable CostsOpinion of Probable Costs$1,383,558$1,389,095$1,138,826TOTAL Annual Costs$341,000$341,000$341,000Total O&M (Per Year)75,00075,00075,000Miscellaneous Repairs and Supplies230,000230,000230,000Power$36,000$36,000$36,000LaborAlternative #3Alternative #2Alternative #1 ItemOperations and Maintenance (O&M) Costs in 2000
Opinion of Probable CostsOpinion of Probable Costs* Cost Index of 1.37 was calculated by the Bureau of Labor Statistics for labor costs$2,333,633$2,343,582$1,895,602TOTAL Annual Costs$467,170$467,170$467,170Total O&M (Per Year)$102,750$102,750$102,750Miscellaneous Repairs and Supplies$315,100$315,100$315,100Power$49,320$49,320$49,320LaborAlternative #3Alternative #2Alternative #1 ItemOperations and Maintenance (O&M) Costs in 2007*
FindingsFindings• The opinion of costs for the construction of the capital improvements is $23,385,000. Annual costs to amortize the capital improvements is $1,876,412 (20yrs., i = 5%).• Operation and maintenance costs are estimated to be $467,170/ year.• Total cost of the project on a per resident basis is estimated at $44.00/month.• Several potential methods of payment to retire the capital costs and annual operation exist.• The opinion of costs for the construction of the capital improvements is $23,385,000. Annual costs to amortize the capital improvements is $1,876,412 (20yrs., i = 5%).• Operation and maintenance costs are estimated to be $467,170/ year.• Total cost of the project on a per resident basis is estimated at $44.00/month.• Several potential methods of payment to retire the capital costs and annual operation exist.
Financing OptionsFinancing OptionsNebraska Natural Resources Commission-Development Fund — Grants/LoansNebraska Cooperative Agreement/Water Action Plan• District Creation-Drainage District – Assessment of project benefits to the designated area• Off-Set Water on the Platte River-Market Water to Platte River Users-- Potential sources include: Downstream Communities and Industry -Market Water to Environmental Agencies-- Potential sources include: Fish and Wildlife Service, Nebraska Game and Parks, State of Nebraska Department of Water Resources/New Depletion PlanNebraska Natural Resources Commission-Development Fund — Grants/LoansNebraska Cooperative Agreement/Water Action Plan• District Creation-Drainage District – Assessment of project benefits to the designated area• Off-Set Water on the Platte River-Market Water to Platte River Users-- Potential sources include: Downstream Communities and Industry -Market Water to Environmental Agencies-- Potential sources include: Fish and Wildlife Service, Nebraska Game and Parks, State of Nebraska Department of Water Resources/New Depletion Plan
Financing OptionsFinancing Options• Utility User FeesWastewater DepartmentWater Department• General FundGeneral Fund — Municipal Bonds• Utility User FeesWastewater DepartmentWater Department• General FundGeneral Fund — Municipal Bonds
Thanks for ListeningThanks for Listening