terraphase
engineering
March 3, 2025
Mr. Dan Sidle
LSA Associates, Inc.
157 Park Place
Point Richmond, California 94801
sent via email to dan.sidle@|sa.net
Subject: Proposal for an Ecological Risk Evaluation of Proposed Sediment Reuse - Refugio Valley Pond, City of Hercules, CA.
Dear Mr. Sidle:
Terraphase Engineering Inc. (Terraphase) is pleased to submit this proposal to LSA Associates, Inc. (LSA) for a limited ecological risk evaluation on the potential reuse of sediment from Refugio Valley Pond, City of Hercules, CA. It is our understanding that one of the disposal options the City of Hercules (City) is contemplating is to place the sediment in a designated open space owned by the City.
Investigative sampling conducted by Terraphase indicates that a subset of samples exhibits concentrations of cadmium, copper, and vanadium above the Regional Water Quality Control Board (RWQCB) Environmental Screening Levels (ELs) for terrestrial habitat. Therefore, this evaluation is recommended to provide a written record demonstrating potential hazards have been evaluated and help guide the City's decision on the open space placement of the sediment.
Scope of Work
Terraphase proposes the following tasks to complete the scope of work.
Task 1: Literature Review
This task will include a review of the basis for the terrestrial ELs. Because these values are used for screening level purposes, they may be based on receptors that are not anticipated to inhabit a particular site or are calculated using overly-conservative exposure assumptions. Based on the outcome of Task 1, we will evaluate the applicability of using alternative input values to develop site-specific risk-based levels, as described further in Task 2.
Because it is not practical to achieve a risk-based level below background levels, this task will also include a search for readily available information on local and/or regional background concentrations of cadmium, copper, and vanadium in soil. Where a background concentration is higher than the calculated risk-based value, the background concentration will be selected as the target level.
Task 2: Risk Estimation and Calculation of Risk-Based Cleanup Levels File: pro-City of Hercules-Refugio Valley Pond-EcoEvaluation- This task will use simple food chain models for a representative bird and mammal to estimate the potential for ecological risk. The risk estimates will generally be conducted in accordance with USEPA and DTSC guidance for ecological risk assessment. Because birds and mammals search for food over a specified area (typically referred to as the receptor's home range), the risk estimates will be based on 1300 Clay Street, Suite 1000 | Oakland, California 94612 | www.terraphase.com March 3, 2025
Mr. Dan Sidle, LSA Associates, Inc.
Proposal for Ecological Risk Assessment Support
average concentrations rather than a single point concentration such as the maximum. Potential exposure will be evaluated by calculating a total dietary intake (TDI) from the ingestion of food and the incidental ingestion of sediment (as soil) while foraging or hunting.
If the estimates indicate the potential for risk, the food chain models can be used to back calculate risk- based levels that are considered protective. If needed, this evaluation will also take into consideration any plans the City has to ameliorate the sediment by blending it with other materials (we will simply "dilute" the concentrations).
Task 3: Technical Memorandum
Terraphase will prepare a draft technical memorandum summarizing the outcome of Tasks 1 and 2 for review by the City. For budgeting purposes, Terraphase has assumed this will involve one round of review by City and preparation of a final draft to serve as a written record demonstrating that potential hazards were adequately considered by the City prior to reuse of the material. This scope does not include efforts for submittal of the final report to, or addressing comments from, the Waterboard.
Schedule
Terraphase is ready to commence with the tasks presented in this proposal immediately following written approval from LSA. We estimate providing the City with a draft technical memorandum approximately 4 to 6 weeks following approval.
Cost Estimate and Terms and Conditions
Based on our current understanding of the scope of work, our proposed cost estimate to complete Tasks 1 through 3 including Terraphase 2025 standard labor rates with a 10% discount is $11,800.
A summary of the costs, by task, is presented in the following table.
Task Estimated Cost
Task 1 - Literature Review $1,800
Task 2 - Risk Estimates $5,300
Task 3 - Technical Memorandum $4,700
Total $11,800
Terraphase will perform the services described in this proposal on a time-and-materials basis in accordance with the terms and conditions of the Subconsultant Agreement between LSA and Terraphase dated December 5, 2024.
Any modifications to the scope, schedule, and budget presented herein that might arise through discussions with the City or the Waterboard will be addressed through change orders. Please sign and return this proposal to Terraphase as our authorization to proceed with the scope of work described herein.
March 3, 2025
Mr. Dan Sidle, LSA Associates, Inc.
Proposal for Ecological Risk Assessment Support
Closing
Terraphase is grateful for the opportunity to continue supporting LSA and the City. If you have any questions or comments regarding this submittal, please contact Chris Jones at [email protected].
Sincerely,
for Terraphase Engineering Inc.
Chris Jones, PE (C89316)
Senior Associate Engineer
cc: Jeff Brown, City of Hercules
David Caneer, SNG Associates
Acceptance of Proposal
The cost, specifications, and conditions outlined herein are satisfactory and are hereby accepted.
Terraphase is authorized to proceed with the work, as specified.
This proposal is hereby accepted by a duly authorized representative of the Client to whom it is addressed:
Signature: Date:
Printed Name:
Title:
Table 1 - Time and Materials Cost Estimate
LSA Associates
Refugio Valley Pond Sediment Risk Evaluation
Task 1:
Task 2: Risk Task 3: Technical
Literature TOTALS
Standard Estimates Memorandum
Category Units Discount Rate Review
2025 Rate
Qty Cost Qty Cost Qty Cost Qty Cost
Labor
Senior Principal Hour 320.00 10% 288.00 288 288
Principal Hour 301.00 10% 270.90 271 542 542 1,355
Senior Associate Hour 282.00 10% 253.80 1,015 1,015 1,015 12 3,046 Associate Hour 264.00 10% 237.60 -
Senior Project Hour 247.00 222.30 889 889 1,778
Project Hour 230.00 207.00
Senior Staff 2 Hour 213.00 191.70 is us is es is es
Senior Staff 1 Hour 193.00 173.70 10 1,737 00 1,390 3,127 Staff 2 Hour 171.00 10% 153.90 is us is is is is us us us us es is us us is es es es us es es Staff 1 Hour 149.00 10% 134.10 536 00 1,073 536 2,146
Senior Technician Hour 156.00 10% 140.40
Technician 3 Hour 136.00 10% 122.40
Technician 2 Hour 114.00 10% 102.60
Technician 1 Hour 96.00 10% 86.40
Senior Editor/ Senior 149.40
Hour 166.00 10% es
Project Coordinator
Editor 2/Project
Coordinator Hour 147.00 10% 132.30 es
2/ Accountant 2
Editor 1/Project
Coordinator Hour 122.00 10% 109.80 110 110
1/Accountant 1
Administrator/Project
Assistant/Billing Hour 103.00 10% 92.70
Specialist
+ Tal Terraphase Labor 1,823 5,256 4,770 11,849
Total Estimated Project Unit Costs $ 1,823 $ 5,256 $ 4,770 11,849 Terraphase Engineering Inc. Page 1 of 1