July 18, 2025 File No: 23-00065
Nathan Armendariz
City of Corona
400 South Vicentia Avenue, Suite 200
Corona, CA 92882
RE: CORONA- ONTARIO AVENUE WIDENING (PO NO. P23003) ADDITIONAL SERVICES REQUEST NO. 01 Dear Mr. Armendariz:
Per your request, Mark Thomas has prepared this additional services letter for the Ontario Avenue Widening at Lincoln Avenue Project (Project). The following items have been requested by the City to be included as part of this project:
1. It was requested that resurfacing be extended from Via Pacifica to South Vicentia Avenue along Ontario Avenue.
2. The design of raised median islands along Ontario Avenue from Oak Avenue to South Vicentia Avenue.
3. Place standard retaining walls at the property frontages affected by the Ontario Avenue widening.
A detailed scope and budget to perform the additional services follows.
Mark Thomas was directed to advance our design efforts under the current not-to-exceed contract in order to continue progress of the 60% design. To assist the City with the timeline to process an amendment for the additional services, but not to disrupt the current staffing and progress of the design, Mark Thomas recommended a ‘net-zero’ budget reallocation of the future PS&E deliverables subtask funding. This would allow the team to move forward with the additional services without delay.
Mark Thomas proceeded with 60% plans, but still required direction from the City for changes in the project limits and wall type. During that time, Mark Thomas proceeded with the design and completed the 60% plans and estimate. Mark Thomas committed staff to the project and attempted to keep production at premium, but we have seen some accrual of extra staff time while waiting to receive final direction related to clarification of scope limits due to previous projects that were completed recently.
While these additional scope limits were not anticipated, Mark Thomas proceeded to perform these additional services and held on localized areas until final scope was clarified and most of this was accomplished by reallocating the budgets noted above. Currently the additional level of effort has been tracked and estimated approximately exceeding 4% (~$25,000) over the project total budget and the City has received the 60% plans and estimate associated with this effort.
As such, we propose to incorporate the clarified scopes of work into the existing budget or potentially discuss other options.
SCOPE OF SERVICES
TASK 2 – RESEARCH EXISTING CONDITIONS
Task 2.6 – Additional Surveying
Mark Thomas’s additional scope of work includes aerial topography for the extended grind and overlay limits along W Ontario Avenue between Via Pacifica Avenue and Oak Avenue.
The City requested for Mark Thomas to analyze two drainage depression areas along W Ontario Avenue and reconstruct two additional ADA ramps along Ontario Avenue at Silver Oak Drive, which will require the need for additional supplemental survey.
Mark Thomas will perform supplemental survey at the locations noted above and requires 1 day of field survey, aerial photogrammetry processing, and survey technician data extraction.
DELIVERABLES
• Supplemental topography for Ontario Avenue between Via Pacifica Avenue and Oak Avenue • Supplemental topography for the two localized depression areas along Ontario Avenue • Supplemental topography for two ADA ramps along Ontario Avenue at Silver Oak Drive TASK 5 – FINAL ENGINEERING/CONSTRUCTION CONTRACT DOCUMENTS Task 5.1 AM#1, 5.2 AM#1, 5.3 AM#1 & 5.4 AM #1 – 60%, 90%, 100% & Final PS&E Additional Plan Production Street Plans and Retaining Wall Details
Mark Thomas’s additional scope of work includes street improvement plans for the new median areas along W Ontario Avenue between Oak Avenue and Lincoln Avenue, two additional ADA ramps along Ontario Avenue at Silver Oak Drive, retaining walls along the eight (8) property frontages affected by the widening, and localized drainage depressions between Oak Avenue and Lincoln Avenue. The additional scope of work proposed under this task will require two (2) additional Street Improvement sheets, seven (7) retaining wall plan and detail sheets, and two (2) construction detail sheets.
Based on the final geometry and comments received on the civil engineering 30% Package Submittal, Mark Thomas will provide plans and estimates of probable construction costs for each design submittal and technical specifications at 90%, 100% and Final submittals.
60% plans will include street improvement plans (in AutoCAD, 40-scale/10-scale). The City has provided direction to use standard wall details including plan view, footing and wall elevations, and typical sections.
At the 90% submittal level, City comments from the 60% submittal will be addressed and incorporated and refinements will be made to the street and wall plans/details. Responses to comments will be prepared and submitted. Retaining wall plans will note existing and proposed utilities and laterals protected-in-place or installed as a part of the project. Estimate will be refined based on comments and continued design and submitted for comment.
City comments from the 90% submittal will be addressed and incorporated into the 100% and Final Submittals.
Responses to comments will be prepared and submitted. All final plan revisions will be made. Updates to the specifications and estimate will be completed.
DELIVERABLES
• Roadway Plans (40-scale, provided in PDF format)
• Retaining Wall Plans and Details (10-scale, provided in PDF format) • Construction Details (5-scale, provided in PDF format) Landscape Improvement Plans
Mark Thomas’s additional scope of work includes planting and irrigation plans for the new median areas along W Ontario Avenue between S Buena Vista Avenue and S Vicentia Avenue and between Oak Avenue and S Lincoln Avenue. The additional scope of work proposed under this task will require six (6) additional sheets, three (3) for landscape and three (3) for irrigation.
Based on the final geometry and comments received on the Preliminary Landscape Plans and civil engineering 30% Package Submittal, LAUD will prepare Landscape Architectural PS&E submittals at the 60%, 90%, 100% and Final milestones.
Sheet Name Number of Sheets Drawing Scale
Street Plans 2 40
Retaining Wall Plans and Details 7 10
Construction Details 2 5
60% plans will include planting plans and irrigation plans (in AutoCAD, 20-scale). Planting plans will include tree, shrub, and groundcover locations, plant list, and plant callouts and quantities.
Irrigation plans will include points of connection locations, mainline layout, pressure loss calculations, and irrigation equipment list. Estimate will be submitted in draft form.
At the 90% submittal level, City comments from the 60% submittal will be addressed and incorporated and refinements will be made to the planting plan. Responses to comments will be prepared and submitted. Irrigation plans will include water use (MWELO) calculations, irrigation controller schedule, irrigation head and lateral layout with pipe sizing.
Estimate will be refined based on comments and continued design and submitted for comment.
City comments from the 90% submittal will be addressed and incorporated into the 100% and Final Submittals.
Responses to comments will be prepared and submitted. All final plan revisions will be made. Updates to the specifications and estimate will be completed.
Mark Thomas LAUD will provide technical specifications and estimates of probable construction costs for each design submittal.
DELIVERABLES
• Planting Plans (20-scale, provided in PDF format)
• Irrigation Plans (20-scale, provided in PDF format)
• Itemized statement of probable construction costs
TASK 6 & 7 - BIDDING SERVICES & ENGINEERING CONSTRUCTION SERVICES Mark Thomas will assist City in providing clarification and preparing information to be used in addenda as needed for questions that may arise during the bidding process and record drawings for the additional out of scope areas added to the scope of the project, and the sheets listed above.
ASSUMPTIONS:
• An arborist report is not a part of this scope to evaluate existing trees and mitigation required for the project. • Landscape treatment for median plantings will be consistent with the rest of the Ontario Avenue corridor.
Customization or alternatives of private property landscape treatments for property owners is not a part of this scope.
• Stormwater plantings/LID treatments are not required and/or included with this additional scope. • Median irrigation will be supplied by existing domestic water running on the north side of W Ontario Avenue within the project area. Capacity, size, and pressure of the domestic water system is assumed to be sufficient to extend to new planting areas.
• Landscape within the right-of-way will be maintained by the City. • Planting and Irrigation details and specifications from the original scope will be utilized for this additional work. • Renderings of the proposed improvements within the private properties affected by these improvements located on the south side of Ontario avenue between Lincoln Avenue and Conejo Street will be prepared in 20 scale as a single effort. Up to 12 hours are allocated for this effort in the original scope. Any additional effort required beyond the initial 12 hours will be requested as an additional service. • Subtask budgets for the additional 60%, 90%, 100% and Final will be determined and allocated for the project budgets and invoice once the additional services has been approved by the City.
Sheet Name Number of Sheets Drawing Scale
Landscape Planting Plans 3 20
Landscape Irrigation Plans 3 20
FEE ESTIMATE:
Attached is our detailed cost breakdown utilizing our originally agreed upon rates.
Thank you for the opportunity to provide this letter for additional services for the Ontario Avenue Widening at Lincoln Avenue Project.
Please give me a call if you need any additional information or have any questions regarding these additional services.
Sincerely,
MARK THOMAS
Paul Mittica, PE
Project Manager
Accepted:
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