Council Communication Office of the City Manager	Date	October 27, 2008
	Agenda Item No. 47A Roll Call No. 08- Communication No. 08-646 Submitted by: William G. Stowe, Assistant City Manager/Public Works/Engineering and Jeb E. Brewer, P.E., City Engineer

AGENDA HEADING:

Approving Professional Services Agreement with Veenstra & Kimm, Inc., for design and construction phase services, for the Court Avenue/Water Street Sewer Separation Project, not to exceed $595,712.

SYNOPSIS:

Recommend Council approval of the Professional Services Agreement with Veenstra & Kimm, Inc. (H. R. Veenstra, Jr., President, 3000 Westown Parkway, West Des Moines, Iowa 50266) for an hourly not-to-exceed amount of $595,712 to provide design and construction phase services of storm sewer improvements and a storm sewer pump station for the Court Avenue/Water Street Sewer Separation Project.

FISCAL IMPACT:

Amount: $595,712

Funding Source: 2008-2009 CIP - New Project Court Ave/Water Street Sewer Separation - STE081: with a transfers from the following projects: $388,000 from CIP Page Storm Water - 14, Storm Water Pump and Trash Rack Replacement - STE076; $42,839 from CIP Page Storm Water - 17, Watershed Studies, STE072; and $169,161 from Easton Detention Basin - STE065.

ADDITIONAL INFORMATION:

Request for Proposals for the Court Avenue/Water Street Sewer Separation Project was issued on August 25, 2008. Five responses were received on September 12, 2008, from Howard R. Green Company, Stanley Consultants, HDR, Inc., Snyder & Associates, and Veenstra & Kimm, Inc.

After evaluating the qualifications of each submitter, all five were interviewed. Veenstra & Kimm, Inc., was selected as the consultant based on their experience and familiarity with the City’s sewer system in the downtown area. City staff has negotiated a contract with Veenstra & Kimm, Inc., to include design and construction phase services in the amount not to exceed $595,712.

The flood protection for this area is a Corps of Engineers’ 100-year design levee. The area is served by a combined (storm and sanitary) sewer system with normal flow directed to the wastewater treatment plant. Under high rain events, the excess flow in the system is diverted to the Des Moines River through a gravity combined sewer overflow (CSO) gate. Localized flooding can occur under certain conditions of heavy rain and sufficiently high river levels when the CSO gate must be closed to prevent flow from the river into the sewer system. Design and construction of a separate storm sewer system and storm pump station can mitigate the incidence and severity of localized flooding.

Due to exceptionally high river levels and extensive localized rains, the combined sewer system in the Court Avenue Area became surcharged and contributed to the localized flooding in the area. By June 6, 2008, the river elevation was such that the river would have flowed into the combined sewer system if the CSO gate at Court Avenue had been opened. These gate structures prevent large scale flooding of the area. Subsequent rainfalls, such as on June 11 and June 12, with the river level high and the CSO gate closed, resulted in flooding depths to four feet on Court Avenue.

During the June 2008 floods, the Wastewater Treatment Plant was processing total sewer flow in excess of the total rated plant capacity of 196 million gallons per day. The sewer system has a twin barrel inverted siphon to transport the normal wastewater flows from the west side downtown combined sewer system to the east side of the Des Moines River. Any flow in excess of the capacity of this inverted siphon is typically discharged at the Court Avenue overflow. During the June 11 and 12 rain events, in addition to the normal discharge at the Court Avenue overflow, sewer water was observed overflowing from manholes and intakes along and south of Court Avenue. Flows were also observed discharging from the storm sewer intakes north of Court Avenue due to high river levels and gate closures on the storm sewers that serve Walnut Street, Locust Street, and Grand Avenue. These events created the flooding in the Court Avenue area and the areas to the south of Court Avenue.

Funding for construction will be programmed through the Capital Improvement Program process.

PREVIOUS COUNCIL ACTION(S):

Date: August 11, 2008

Roll Call Number: 08-1470

Action: Request for Proposals (RFP) for design and construction phase services of storm sewer improvements and a storm sewer pump station in vicinity of Water Street and Court Avenue. (Council Communication No. 08-498) Moved by Hensley to adopt. Motion Carried 7-0.

BOARD/COMMISSION ACTION(S): NONE

ANTICIPATED ACTIONS AND FUTURE COMMITMENTS:

Anticipated actions include receive and file of bids, designate lowest bidder, approve contract and bond, partial payments to the contractor, and final acceptance of work

For more information on this and other agenda items, please call the City Clerk’s Office at 515-283-4209 or visit the Clerk’s Office on the second floor of City Hall, 400 Robert D Ray Drive. Council agendas are available to the public at the City Clerk’s Office on Thursday afternoon preceding Monday’s Council meeting. Citizens can also request to receive meeting notices and agendas by email by calling the Clerk’s Office or sending their request via email to cityclerk@dmgov.org.