Report Prepared by: Michael R. Beltran II, PE, City Engineer
Title
SUBJECT: Approval of Additional Contingency in the Amount of $168,558 for Additional Work Which is Reflected in Change Order #3 Associated with the Alpine Dr - G St. to Wainwright Ave. Improvements, Project No. 119006
REPORT IN BRIEF
Considers approving an increase to the contingency in the amount of $168,558 for City Project No. 119006 - Alpine Drive, G Street to Wainwright Avenue Improvements.
RECOMMENDATION
City Council - Adopt a motion authorizing the City Manager or designee to execute the necessary documents and to approve change orders up to a total contingency amount of $229,706.03. An increase in contingency of $168,558.
Body
ALTERNATIVES
1. Approve, as recommended by staff; or,
2. Approve, subject to conditions other than recommended by staff (identify specific findings and/or conditions amended to be addressed in the motion); or,
3. Deny; or,
4. Refer to staff for reconsideration of specific items (specific items to be addressed in the motion); or,
5. Continue to a future meeting (date and time to be specified in the motion).
AUTHORITY
Charter of the City of Merced, Article XI, Section 1109 - Contracts on Public Works, and Merced Municipal Code Chapter 3.04, Article IV - Public Works Contracts.
CITY COUNCIL PRIORITIES
As provided for in the 2020-21 Adopted Budget.
DISCUSSION
The increase in the contingency for the Alpine Drive - G Street to Wainwright Avenue project by $168,558 is due to the following items:
1. Quantity adjustments;
2. Water service line poly coating and tracer wire;
3. Addition of a sewer line to the project; and,
4. Unstable subgrade throughout the project site after paving had been started.
The above items are addressed in more detail below:
1. Quantity Adjustments - Normally in construction contracts there are quantity adjustments that need to be made to concrete sidewalks, access ramps, driveways, asphalt concrete etc. This project is not different. There were quantity adjustments that were made to all the items mentioned.
2. Recently the water department has requested that we use poly coated copper for water services instead of standard copper. The poly coating is blue which signifies that the line is a water line, making it easier for city crews and other contractors to identify what is running through the pipe. Additionally, the poly coating provides an additional layer of protection for the copper piping. Tracer wire was also added to the water main to allow for locating the water once buried and covered by the new roadway. The engineering department is including these items in all future projects.
3. The sewer department requested that a 128-foot section of sewer pipe be replaced after the line was evaluated with a camera. There was deterioration in the pipe and staff believed that the pipe should be replaced.
4. During paving operations, there are many truck loads of asphalt concrete (AC) that are delivered. The first loads that were delivered and placed on the first section of roadway from G Street to McCombs Drive were fine. Soon after the first few loads, the crews notice that the subgrade (base and native soil) began to “pump.” A “pumping” subgrade is similar in concept to trying to compact something on a mattress, difficult if not impossible, and is caused by excessive moisture withing the soil structure. This type of condition may not be recognizable during the initial construction as there is not repeated heavy construction equipment on the soil. When the repetitions from heavy equipment such as trucks delivering AC become too much for the soil structure, the soil becomes unstable. This was the case on this project. With “pumping” soil there are a few ways that the soil can be stabilized:
a. Wait for water to percolate (water draining out of soil) or evaporate. While this option is probably the least expensive, there is no way to know how much time it will take to do this with the clay soil that we have in the City.
b. Remove the areas of pumping soil to a depth of at least 12 inches, lay a geotextile, which helps stabilize the soil, and place aggregate base on top.
c. Reconstruct the entire roadway section using lime or cement treatment. This results in the best foundation for the pavement but is also the most expensive option. Specialty contractors to perform this work are generally weeks if not months out in scheduling.
The chosen method to stabilize the subgrade was option “b.” Unfortunately, there was also additional AC that the plant had loaded into trucks (approximately 200 tons) that needed to be placed or thrown out. The City opted for this AC to be used in dig out areas to stabilize the subgrade. Although it would have been best to use this AC for actual paving, it was not thrown out and wasted.
Unfortunately, these types of issues are difficult at best to predict and are unforeseen. This item alone cost $168,558.
The following was approved by the City Council on October 19, 2020:
The work to be done consists of the removal of 3-inches of existing asphalt concrete and installation of a 3-inch asphalt concrete overlay. The work also includes removal of existing curb & gutter, sidewalk, and valley gutters and installation of ADA ramps, curb & gutter, sidewalk, striping, signage and valley gutters.
Staff prepared plans and specifications, and bids were opened on September 22, 2020, with a total of six bid submissions:
1. TBS Contractors. $ 611,480.27
2. Rolfe Construction Company, Inc. $ 656,910.00
3. United Pavement Maintenance, Inc. $ 741,959.00
4. Phase 1 Construction $ 747,471.60
5. George Reed, Inc. $ 811,808.00
6. Mid Cal Pipeline & Utilities, Inc. $ 893,205.00
The engineer’s estimate for construction was $626,000
The following is the proposed budget for the project:
|
Construction |
$ $611,480.27 |
|
Contingency |
$ $ 61,148.03 |
|
Engineering, Testing & Inspection |
$ $ 30,574.01 |
|
TOTAL: |
$ $703,202.31 |
This project will require the contractor to notify property owners by door hangers and barricades of when work will be done to ensure vehicles are removed from the street.
IMPACT ON CITY RESOURCES
This project was established as a Capital Improvement Project to be funded by Measure V, RSTP, SB1, Sewer and Water Enterprise funds. Funding is available to fund the change order.
ATTACHMENTS
1. 119006 - CO#3