Big Hollow Manhole Seepage Remediation
- Department: Conservation
- Deadline: November 3, 2026 at 3:00 p.m.
SUMMARY AND BACKGROUND
Des Moines County Conservation (DMCC) is soliciting proposals from qualified contractors to remediate water seepage occurring at specific manholes within Big Hollow Recreation Area. The purpose of this RFP is to engage contractors capable of sealing the annular space inside the manholes and constructing concrete collars around the exterior of affected manholes as shown in Attachment A. The project includes confined-space work in a sewer environment; therefore, proper entry procedures, permits, and safety protocols must be strictly followed.
PROPOSAL GUIDELINES
- This RFP represents the requirements for an open and competitive process.
- Proposals will be accepted until 3:00 PM CST on November 3, 2026.
- Any proposals received after this date and time will not be considered.
- All proposals must be signed by an authorized representative of the bidding company.
- DMCC reserves the right to not award the contract if bids do not meet expectations or budget.
PROJECT PURPOSE AND DESCRIPTION
The goal of this project is to seal the space between the concrete manhole and the PVC riser to prevent groundwater infiltration. Additionally, a reinforced concrete collar must be installed on the exterior of each manhole to counteract buoyant forces associated with high groundwater conditions. The attached plan (Attachment A) provides engineering details for these tasks. Contractors are HIGHLY encouraged to visit the site prior to submitting a bid.
Completion during the 2026 construction season is preferred if weather conditions allow; however, the required completion date for the project is April 1, 2027.
PROJECT SCOPE
- Clean and prepare interior annular space for sealing.
- Apply appropriate sealant or grout to create watertight interior seal.
- Excavate around manholes as needed to install concrete collar.
- Construct exterior reinforced concrete collar per Attachment A.
- Backfill and restore site to original condition.
- Adhere to all confined-space entry, permitting, and safety requirements.
