Memorandum

City of Lawrence

Public Works

 

TO:

Dave Corliss, Debbie Van Saun, Charles Soules, Tammy Bennett, Dena Mezger, Shoeb Uddin

FROM:

Matt Bond

Date:

April 20, 2007

RE:

Stormwater Utility Overview

 

 

This memo provides a requested overview of the stormwater utility including; capital improvement projects, the maintenance of existing stormwater infrastructure, recommendations concerning the North Lawrence Drainage Study and the recertification of the North Lawrence Kansas River Levee.

 

CAPITAL IMPROVEMENT PROJECTS

The stormwater utility is currently paying off two separate general obligation bonds resulting from the completion of capital improvement projects.  These double bond payments continue through the end of 2009 and the payoff for the complete debt service runs through the end of the year 2017 (refer to the attachment).  Since current expenditures exceed revenues and the fund balance forward is being spent down, implementation of any new capital improvement projects will be delayed.  Without additional bond purchasing, a stormwater utility rate increase or some sort of additional funding mechanism, higher end capital improvement projects will not be possible in the immediate future.  Examples include the following projects:

 

Ø      23rd & Ousdahl (1996 Estimate - $1,022,800) (w/possibly partial grant funding)

Ø      Maple Street Pump Station (NLDS-System 6) (Dec. 2005 estimate - $4,375,000)

Ø      8th/9th and Holiday (1996 Estimate - $130,000)

Ø      Alabama, 17th to Naismith Drive (1996 Estimate - $2,563,100)

Ø      Maple Lane, 19th to Brook (1996 Estimate - $1,080,000)

 

When opportunities to stretch funding present themselves, such as the 2nd and Locust state project, storm water upgrades will be implemented when possible.  Additionally smaller projects can be kept for in-house engineering and construction.  The cost of future capital improvement projects will need to be balanced between nuisance flooding and storm sewer infrastructure maintenance.  Projects alleviating flooding problems which cause structure damage will be given the highest priority. 

 

EXISTING STORMWATER INFRASTRUCTURE

There are 137.57 miles of storm sewer lines within the city.  Of these existing storm sewer pipes 48% of them are 25 years or older and 17% are 50 years or older.  A systematic inspection of all curb inlets will take place over the next year.  Upon completion of the data collection; pipes, curb inlets and junction boxes will be evaluated to structure a maintenance and replacement program.  To help comprehend the size of the task being undertaken the current GIS data is listed below:

 

Ø      4385 curb inlets

Ø      249 area inlets

Ø      1287 manhole/junction box

Ø      1088 end sections

 

In addition to structuring a formal maintenance program, staff will focus on long range watershed planning in the urban growth area as time permits.  Sub water sheds will be modeled to help identify future potential stormwater problem areas.

 

NORTH LAWRENCE DRAINAGE STUDY

After reviewing the North Lawrence Drainage Study (NLDS) the following overview outlines both short and long term recommendations with regards to current flooding and future development in North Lawrence.  The NLDS has provided a list of recommended improvements totaling $41 million (2005 estimate).  It is not fiscally possible to finance all of these recommended improvements at this time.  Staff continues to work on incorporating the priorities identified in the NLDS with the city wide projects identified in the 1996 master plan.  The executive summary of the NLDS lists the following four major recommendations which directly affect future development in North Lawrence. 

 

Ø      “Drainage from north of 24/40 Highway should be cutoff by the highway embankment and the water should be pumped over the levee at a point just east of the 24/40 intersection to reduce the burden on the 2nd Street Pump Station.”

 

Ø      “Future developments in the watershed should maintain the current conveyance levels in the 100-yr floodplain – development should not reduce the capacity for floodplain storage.”

 

Ø      “The City should purchase parcels of land as necessary for use as dedicated ponding area.”

 

Ø      “Major roads and hydraulic structures should be improved to meet the current APWA criteria with regard to overtopping during the 100-year event, in order to provide adequate emergency services to the area.”

 

Relative to the first point, raising the 24/40 highway embankment west of US-59 would cut off the flow of water into the City from the north but at an estimated project cost of $24,802,000.  It would be reasonable to let the development of the property north of 24/40 Highway dictate when this will take place and at least share in the cost.  This same reasoning can be applied to upgrading the 2nd Street Pump Station and its downstream piping. 

 

Staff concurs with the second recommendation regarding floodplain conveyance but takes exception to a related statement.  The executive summary of the NLDS, states “Due to the extensive hydraulic studies detailed in this report, it would not be necessary for developers to conduct individual studies, as long as the general recommendations of this study are followed (i.e. conveyance needs to be maintained with the floodplain).”  Until recommended “Internal Systems” can be completed and are operational it is recommended that a Hydrologic & Hydraulic (H&H) Study continue to be a requirement for any future development located within the floodplain in North Lawrence.  Additional development within the floodplain has the potential to raise the overall water surface elevation for surrounding properties resulting in property damage.  The continued requirement of an H&H study will help to identify these situations.  For areas outside the floodplain the report can serve as the H&H study on a site specific basis provided that current conveyance levels are maintained and that there is no net reduction in overall floodplain storage.

 

The third recommendation from the NLDS was the acquisition of land to pond stormwater.  It is recommended that as opportunities for property acquisition present themselves that the City evaluate potential benefits for stormwater detention.

 

Total compliance with the fourth and final recommendation of improving major roads and hydraulic structures to meet the current APWA criteria will not be possible until construction of or improvements to pump stations north of 24/40, at 6th & Maple and on 2nd Street are complete.  Refer to “NLDS Recommendations” memorandum dated February 16, 2007 for more specific details.

 

An important fact to remember during any system upgrade: “improvements are to generally be made in a downstream to upstream manner within the system, as there is no advantage trying to deliver more flow to a downstream component that cannot convey the existing flow.”

 

LEVEE RECERTIFICATION

FEMA has mandated that the levee protecting North Lawrence be recertified by June 2009.  Unfortunately no funding has been provided by either the US Army Corps of Engineers or FEMA to complete the process.  The cost for recertification of the levee could be several hundred thousand dollars.  Failing to meet the recertification process would remove the levee from flood insurance protection maps which would place North Lawrence in the flood plain.  An extension of the deadline as well as funding sources for the recertification will need to be identified as soon as possible.

 

SUMMARY

It will not be possible to fund new stormwater capital improvement projects for the immediate future with double bond payments lasting through the end of 2009. In order to better identify and plan for future storm sewer maintenance, a comprehensive storm sewer infrastructure maintenance program will be developed.  With regards to the North Lawrence Drainage Study (NLDS), staff recommends that development of the property north of 24/40 Highway dictate when NLDS recommendations take place and that developers at least share in the cost.  Hydrologic & Hydraulic (H&H) studies will continue to be required for proposed future developments in the floodplain. For areas outside the floodplain the report can serve as the H&H study on a site specific basis provided that current conveyance levels are maintained and that there is no net reduction in overall floodplain storage.  The City Commission will need to provide direction in 2007 & 2008 on a storm water capital improvement project prioritization blending the NLDS and the 1996 Master Plan.  Identifying and acquiring funding for the recertification of the levee as soon as possible is critical particularly if an extension of the deadline cannot be extended.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Storm Water

Debt Service Schedule

Year

Principal

Interest

Total

2006 Issue

Total Debt w/new issue

2006

1,015,799

303,605

1,319,404

 

 

2007

1,042,629

269,116

1,311,745

25,000

1,336,745

2008

1,015,313

227,399

1,242,712

25,000

1,267,712

2009

650,718

187,736

838,454

25,000

863,454

2010

546,165

163,198

709,363

25,000

734,363

2011

559,640

144,838

704,478

25,000

729,478

2012

575,371

126,852

702,224

25,000

727,224

2013

594,250

107,545

701,794

25,000

726,794

2014

613,128

87,175

700,302

25,000

725,302

2015

635,152

65,715

700,867

25,000

725,867

2016

659,290

42,806

702,096

25,000

727,096

2017

489,733

18,365

508,098

25,000

533,098