TRANSIT DRYWELL MANHOLE REPAIR

2026-11-03

The selected contractor shall provide best practice , methods , and means to provide labor , equipment and all other incidentals necessary to provide services to remove and replace 3 manhole concentric cones on 3 separate drywell systems around the Transit Facility . Great care shall be taken during this project to not compromise the drywell drainage system ; A . Demolition ; 1 . Saw cut asphalt approximately 10 ’ x 10 ’ around each of the 3 drywell manholes requiring repair and maintenance 1 . ( 1 ) to the North of the building , 2 . ( 1 ) NW corner of building , 3 . ( 1 ) SW corner of building , as represented in plan P2 . 1 supplied in request for proposal documents . Remove asphalt debris and dispose offsite at contractor ’ s expense . 2 . Expose and remove manhole ring , riser rings , and cover , clean and set aside to be used for reassembly ; 3 . Excavate around top section of concrete concentric cone section of each of the 3 drywells and remove concrete concentric cone section and dispose of offsite at contractor ’ s expense ; 4 . Set excavation spoils aside to be reused for backfilling of completed repairs for this project ; B . Material Selection ; 1 . Reinforced precast 48 ” x 30 ” concrete conical manhole sections to be used for replacement of existing failed system . All reinforced precast must meet the American Society for Testing and Materials standard specification for circular precast reinforced concrete manhole sections ( ASTM C - 478 ); 2 . Butyl joint sealant tape to be used between riser sections , installation to follow manufacturers guidelines and conform to American Association of State Highway and Transportation Officials ( AASHTO M198 ) joints for circular concrete ; 3 . Class 6 road base to be used for base course of asphalt ; 4 . Grade SX , PG58 - 28 hot mix asphalt to be for planned asphalt patches of the 10 ’ x 10 ’ excavated repair areas at the 3 drywell locations . C . Manhole Repair / Reassembly ; Great care will be adhered to while reassembly is occurring to ensure drywell drainage system integrity is not compromised during the repair process ; Precast Manhole Sections ; 1 . Install concrete manhole sections , joints , and gaskets in accordance with manufacturer ' s printed recommendations . 2 . Install precast adjustment rings above tops of cones or flat - top sections as required to adjust finished elevation and to support manhole frame . 3 . Seal any lifting holes with non - shrink grout . 4 . Precast concrete grade rings shall be permitted to achieve the required grade . Grade rings shall not be permitted to more than 12 - inches . 5 . External joint wrap all riser joints to ensure seal . No grout is permitted on the interior of manhole riser joints . 6 . Provide sealing materials between precast concrete adjustment ring and manhole cover frame in accordance with ASTM C443 . Manhole Frame and Adjustment Rings ; 1 . Combine precast concrete or HDPE high density polyethylene manhole adjustment rings so elevation of insta led casting cover matches pavement surface . Seal between concrete adjustment ring and precast top section with non - shrink grout ; do not use mortar between adjustment rings . Apply latex - based bonding agent to precast concrete surfaces joined with non - shrink grout . Set cast iron frame on adjustment ring in bed of pre - approved sealant material . Install sealant bed consisting of two beds of sealant , each bead having minimum dimensions of 1 / 2 - inch and ½ - wide . 2 . Wrap manhole frame and adjustment rings with pre - approved external sealing material , minimum 3 - inches beyond joint between ring and frame and adjustment rings and precast section . Backfill ; 1 . Place and compact excavated backfill materials in the areas of excavation surrounding manholes in accordance with requirements of Section 31 23 33 – Trenching and Backfilling . 2 . Fill materials should be placed in lifts no greater than 8 ” ( loose thickness ) at the proper moisture level content and compacted prior to the placement of the next lift . 3 . Compact backfill material to achieve 95 % compaction rate , while keeping manhole sections from shifting from plumb and level ; Protection ; 1 . Protect manholes from damage until Work has been accepted . Repair damage to manholes at no additional cost to OWNER .

Rocky Mountain E-Purchasing System

2026-05-06