Manhattan Virtual Industry Day UNOFFICIAL SLIDES.pptx

Manhattan Flood Risk Management Project Virtual Industry Day

Manhattan PDT March 31, 2021

Industry Day Info Only

Agenda (Please note the information in this briefing is just to provide context and general information. The solicitation will have the exact requirements and specs!

History

Project Overview

Contracting Overview

Sand Drains

Underseepage Berms

Levee Raise

Relief Wells

Structures/Gatewells

Site Visit

Closing

History of Manhattan flooding City of Manhattan lies at the confluence of the Big Blue River and the Kansas River.

Both rivers have a history of repeated and catastrophic flooding.

Tuttle Creek Lake lies 6 miles north of Manhattan. This lake system is critical to the Corps’ flood risk management mission.

Major flooding of Manhattan occurred in 1903 and 1951.

1993 Record Flood Near overtopping on Big Blue reach Pin boils and seepage along Big Blue and KS River reaches

Project overview Levee raises along the Big Blue and Kansas River: Sand drains to mitigate stability issues

Underseepage: 28 reliefs wells and 8,000 linear feet of underseepage berms

Gatewells: 6 total

See graphic on the next slide describing the overview

Levee Raise – STA 10+00 - 80+00

Levee Raise – STA 131+00 to 270+00

Relief Wells Underseepage Berms Ponding Ditch Gatewell Replacement Gatewell Modification Gatewell Raise Only New Gatewell Sandbag Gap Sill Stoplog Closure (UPRR)

Manhattan, KS FRM Design Features

Contracting information Invitation For Bid (IFB)

Bonding requirement

Pre-solicitation posted on beta.sam.gov on 17 March 21 (W912DQ21B1002)

Joint ventures, teaming, and partnering advantages

SAM.Gov

Register or Update now due to new requirements

Changes coming in May 2021 and April 2022

Procurement Technical Assistance Centers

Assist Small Businesses with variety of issues including SAM.GOV Registration

To Find an Office nearest you https://www.aptac-us.org/

SAND DRAINS FOR STABILITY

8,700 linear feet of sand drains will be installed. The drains vary between 2 and 4 feet tall, and 10 to 14 feet wide.

Sand drains will be installed from station 40+00 to 46+00 and 199+00 to 272+00.

Sand drains used to improve levee stability in areas where real estate does not easily allow stability berms. Stability berms are typically 10-20 feet wide. In areas where buildings are adjacent to the levee, these berms are less feasible than installing sand drains.

Sand drain material will be ASTM C33 type concrete sand. This meets filter criteria between the adjacent soils and will prevent the drains from becoming congested.

Stability without sand drain (FS = 1.3) Stability with sand drain (FS = 1.6)

Underseepage Berms Underseepage berms required in areas which have previously experience poor flood performance and in areas where the levee fails to meet required factor of safety checks.

The berms are a minimum 150 feet wide (from levee toe), 3 feet tall at levee toe, and 1-foot at the end of the berm.

Station ranges include: 120+00 to 149+50, 161+00 to 184+00, 194+88 to 198+40, 228+00 to 252+40.

12 inches of topsoil stripped and placed on top of underseepage berm for farming.

Berm material should be as pervious or more pervious than underlying soil in order to allow seepage dissipation.

Levee Raise A raise of the Manhattan FRM is required to meet the hydraulic design height.

The raise varies between approximately 0 and 3 feet in height with the largest raise being along the Big Blue River 6+00 to 80+00, and 131+00 to 272+50

Between stations 6+00 and 80+00 the raise will consist of over-steepened slopes centered over the levee centerline From station 131+00 to 272+50, the raise will consist of mainly landside levee raise with occasional transition to riverside levee raise where real estate permits.

Relief Well Installation Twenty-eight relief wells will be installed. The wells are 12 inches in diameter and consist of 60 and 30-Slot stainless steel wire wrapped screens and stainless steel risers.

The wells will be installed using reverse rotary methods.

Excavated pits for drill cuttings are not allowed; only portable sumps are allowed.

Filter pack will be tremie placed, then a bentonite seal, and the rest backfilled with grout to ground surface.

Some wells will have a welded T outfall and some will have protective manhole covers.

Wells will be developed and pump tested.

Completed wells will be accepted after passing a plumbness and alignment test, achieving typical well development criteria, and successful pumping tests.

General Structural scope Construction of new junction boxes, and gatewells (including 1 GW for dual 10’x8’ box culverts).

Wall strengthening or wall extension to several existing gatewells.

Several new Inlet and Outlet structures with flapgates.

Construction of concrete sills across streets.

Concrete Sill Section

Typical Gatewell Wall Strengthening

Site visit (TENTATIVE DATE) Early-Mid May 2021

Walk/drive the site.

See current features and talk new features Date may change based on a variety of reasons

Questions from the site visit can be submitted via ProjNet. Information about accessing ProjNet will be found in the solicitation.

Advertisement and award (Tentative Dates) April – June 2021 Advertisement

June - July 2021 Bid Opening

July 2021 Contract Award

Questions For further information please contact

Mr. Dave Best, David.m.best@usace.army.mil

Mr. Willie Hodges, Willie.e.hodges@usace.army.mil image4.png image5.png image6.png image10.jpeg image11.jpeg image12.png image13.png image14.png image15.png image16.png image17.png image18.png image19.png image20.png image21.png image22.png image23.png image24.png image25.png image26.png image27.jpeg image28.jpeg image29.jpeg image30.png image31.png image11.emf image12.emf image13.emf image1.png image2.png image3.png image7.png image8.png image9.png