Memorandum

City of Lawrence

Utilities Department

 

To:

David L. Corliss, City Manager

From:

Philip Ciesielski

cc:

Debbie Van Saun

Dave Wagner

Date:

March 5, 2007

Re:

Baldwin Creek No.1 Sanitary Sewer Benefit District – Additional Sanitary Sewer Flow Capacity; West Baldwin Creek Sanitary Sewer Interceptor

 

The following outlines the recommended plan to provide sanitary sewer service to the developing area in Northwest Lawrence that extends approximately 1 mile north of 6th Street, and is bounded on the east by Queens Road, and the west by the South Lawrence Trafficway.  The recommendations are based on the 2003 Wastewater Master Plan, the May 2006 Draft Northwest Area Master Plan Update by Black & Veatch and recent implementation of the Pump Station PS48 project.

 

Initial efforts to provide sanitary sewer capacity to this area included the creation of the Baldwin Creek No.1 Sanitary Sewer Benefit District (BC1 Benefit District) and the construction of Pump Station PS45 with a capacity of 1.1 MGD (million gallons per day).  The total project cost for the BC1 Benefit District was $354,417.37.  PS45 was accepted and put into service in August of 2002.  To date there has been no development related construction within this benefit district and PS45 has yet have sanitary sewer services connected to it.  Pending development requests in the BC1 Benefit District will exceed the existing pumping capacity of PS45 by approximately 0.7 MGD.  The table below indicates; the pending development, its capacity participation in the BC1 Benefit District, the developments capacity required in excess of this participation, and the cost associated with the additional capacity per the improvements recommended in this memo.

 

Development         PS45 Flow Participation         Developed Flow        Add’l Required

                                      gpm                              gpm                     gpm

Mercato                            400                               575                      175

Oregon Trail                      191                               332                      141

RootLLC/Graham                23                                 53                       30

Turner                              46                                 102                      56

Loges Add’n                       155                               236                      81

 

Utilizing current proposed land use and population information, the Northwest Area Master Plan Update evaluated options for the extension of sanitary sewer service to the Northwest area of Lawrence, including the ability to accommodate flows in excess of PS45’s current capacity.  The recommended option continues to utilize PS45 in its current configuration.  Flows in excess of PS45’s capacity will be accommodated through the extension of gravity sanitary sewer interceptor lines from the currently under construction PS48 to the BC1 Benefit District area.  PS48 would convey these flows to the existing PS16, located at 6th & Kentucky, and from there the flows would be pumped to the Wastewater Treatment Plant on E. 8th Street.  PS16 is currently under going a planned expansion from a capacity of 8 MGD to 18 MGD.  Part of the driver for this expansion, which was recommended in the 2003 Wastewater Master Plan, was the pumping of additional Northwest area flows from what is the PS48 facility.

 

Efforts to estimate the project cost based on updated alignment information, pipe size and aerial photography has resulted in a $3.4 million dollar project estimate. The proposed interceptor project and cost is based on pipe sized and constructed that would provide service to an area in excess of the BC1 Benefit District.  The cost of these improvements to the BC1 Benefit District for flows in excess of PS45’s capacity is the area’s percentage contribution based on its flow relative to the total capacity of the pipe segments.  These costs are outlined in the table below.  It is estimated the BC1 Benefit District’s share of the gravity interceptor line would be approximately $321,350.00. Similar to the PS48 project, the full cost of the proposed gravity interceptor project will be recovered over time as new developments in the drainage area make connections to the line and PS48.

 

                             Cost for Add’l Capacity

                             via West Baldwin

Development            Creek Interceptor

Mercato                  $116,431

Oregon Trail             $93,810

RootLLC/Graham       $19,960

Turner                    $37,258

Loges Add’n             $53,891

 

PS48 and its forcemain are being constructed with an initial firm capacity of approximately 6.2 MGD.  The pump station is being constructed to accommodate expanded pumping capabilities and the site is situated to allow for the construction of future wet weather flow storage basins.  The initial gravity service area to PS48, which includes the areas contributing to the Free State Interceptor and the undeveloped areas to the south and east of PS48, have the potential to contribute a peak wastewater flow of approximately 3.0 MGD. Addition of the 0.7 MGD flow from the BC1 Benefit District to PS48 would leave 2.5 MGD of the pump station’s initial capacity for future growth.    

 

The costs represented in this document do not include the public improvements required within the BC1 Benefit District to collect the sanitary sewer flows and convey them to PS45 and the proposed gravity interceptors.

 

The recommended improvements are in accordance with the recommendations in the 2003 Wastewater Master Plan and the May 2006 Draft Northwest Area Master Plan Update by Black & Veatch.  The construction of the proposed gravity interceptor to PS48 also positions the Northwest Area of Lawrence for additional development in the Baldwin Creek Benefit Drainage Basins.

 

Staff is requesting City Commission authorization to advertise a Request for Proposals for Design-Build teams for the Preliminary Design and submission of a Guaranteed Maximum Price for construction of the West Baldwin Creek Interceptor Sewer project.   

 

Attach:                   Map of Area