ADDENDUM #1 North County Line Road Over Little Thompson River Low Flow Crossing BID # 6888-18

September 19, 2018

The attached addendum supersedes the original Information and Specifications regarding BID # 6888-18 where it adds to, deletes from, clarifies or otherwise modifies. All other conditions and any previous addendums shall remain unchanged.

1. Question: Would an alternative Modular steel truss Bridge be allowed to be used instead of the large multiple CMP culverts. The bridge is a rapidly assembled and installed steel structure with an epoxy – aggregate coated solid top steel decked bridge deck panels. The steel is hot dipped galvanized (ASTM-123) for long life and low maintenance.

ANSWER: We are not able to redesign the project to accommodate this option.

2. Question: When is the anticipated start and end dates for this project?

ANSWER: We anticipate beginning construction mid-fall and there is no specific end date for the project.

3. Question: Is there a pre-bid for this project?

ANSWER: No.

4. Question: Wanted to double check that there is only 1 document available for this project. Please let me know.

ANSWER: More documents are attached and include:

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5. Question: Are there plans for this project? Pre-bid?

ANSWER: Plans are located at https://www.dropbox.com/s/0aqa12srqwtohia/NCL%7E18.08.28%7EAdvertise ment.PlanSet.pdf?dl=0. This link is located on Overall Page 77 (following Page A-71) of the bid documents. There is no pre-bid.

6. Question: Plans indicate All structural steel shall conform to ATM A36 Except: Wide Flange Shapes ASTM A992 GR. 50 Pipe columns ASTM A53, Grade B HSS / Tube columns / beams ASTM A500, Grade B

From my interpretation, this is Carbon steel (non-Weathering) – what is the proposed finish for the steel?? Painted, galvanized, powder coated?

ANSWER: There is no structural steel anticipated for this project.

7. Question: What is the sand blast clean prep for the steel? SP6? SP7? Thank you in advance for your time and consideration?

ANSWER: There is no steel to be sandblasted for this project.

8. Question: Is the project location suspected to be contaminated with any of the hazardous substances as listed on page 72 of the BID?

ANSWER: Revision of Section 250, Environmental, Health and Safety Management is a CDOT Standard Special Provision in the event any contamination is found on site. See attached reports specific to this project for additional information for environmental considerations.

9. Question: Please provide the Geotechnical Engineering Report, Terracon Project Number 22135032.

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ANSWER: See provided report.

10. Question: Page 22 of the BID states “All insurance policies in this section shall name Boulder County and JUB Engineers, Inc as additional insured,”, Page 23 states “Boulder County and J-U-B Engineers shall be named as an additional insured for General Liability and Pollution Liability, as designated in the contract.”, and Page 86 states “Boulder County shall be named as an additional insured for General Liability and Pollution Liability, as designated in the contract.”. Please clarify as to which specification is to be followed.

ANSWER: Both Boulder County and J-U-B Engineers, Inc. shall be additionally insured. Changes for clarification shall be as given written below.

• Page 21 (A-16) of the project special provisions currently states, “All insurance policies in this section shall name Boulder County and JUB Engineers, Inc as additional insured.”

o This statement shall change to “County of Boulder, State of Colorado, A Body Corporate and Politic and J-U-B Engineers, Inc. are additional insured as respects general liability and pollution liability. Additional insured shall be endorsed to the policy.”

o See attached, “Revision of Section 107, Responsibility of Damage Claims, Insurance Types and Coverage,” dated September 19, 2018 below

• Page 22 (A-17) of the project special provisions currently states, “Boulder County and J-U-B Engineers shall be named as an additional insured for General Liability and Pollution Liability, as designated in the contract. Additional insured shall be endorsed to the policy.”

o This statement shall change to “County of Boulder, State of Colorado, A Body Corporate and Politic and J-U-B Engineers, Inc. are additional insured as respects general liability and pollution liability. Additional insured shall be endorsed to the policy.”

o See attached, “Revision of Section 107, Responsibility of Damage Claims, Insurance Types and Coverage,” dated September 19, 2018 below

• Page 78 of the Insurance and W-9 Requirements in the Bid documents does not indicate who shall be additionally insured. This statement shall be added to the Insurance and W-9 Requirements located in the Bid

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Documents, “County of Boulder, State of Colorado, A Body Corporate and Politic and J-U-B Engineers, Inc. are additional insured as respects general liability and pollution liability. Additional insured shall be endorsed to the policy.”

• Page 86 states of the Sample Contract currently states, “Boulder County shall be named as an additional insured for General Liability and Pollution Liability, as designated in the contract,” and, “County of Boulder, State of Colorado, a body corporate and politic, is named as Additional Insured.” These statements shall be changed to the following, “County of Boulder, State of Colorado, A Body Corporate and Politic and J-U-B Engineers, Inc. are additional insured as respects general liability and pollution liability,” and to “County of Boulder, State of Colorado, a body corporate and politic and J-U-B Engineers, Inc. is named as Additional Insured.”

11. Question: Please provide the Colorado Senate Bill 40 Certification obtained for this project showing special provisions.

ANSWER: See provided report.

12. Question: Please provide the US Army Corps of Engineers 404 Permit obtained for this project showing special provisions.

ANSWER: See provided report.

13. Question: When is the NTP anticipated to be issued?

ANSWER: The NTP is anticipated to be issued in mid-fall.

14. Question: The contract schedule appears to be somewhat aggressive with regard to the amount of work required to take place before mobilizing on-onsite and making any progress. Can additional contract days be considered to account for: • Sub-Contractor contract preparation and execution? • Construction Plan Submittal Preparation and review by the County? • Dewatering Plan Submittal Preparation and review by the County? • Potholing and Coordination with Utility Companies? • Shop Drawing Submittal Preparation and review by County? • Material submittal preparation and review by County? • Pre-Con Meeting? • Sampling and Testing of Onsite Material (Typically a 2-week turnaround from private lab) for approval for embankment by County? • Applying for and obtaining a dewatering permit (30-Day turnaround)? • Power washing all equipment to be used on site prior to mobilizing?

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• Concrete curing (28-Day Strength)?

ANSWER: Work days will start on the first day of actual work onsite. Items a thru g and items i & j are anticipated to occur before the first day of work onsite. Testing of onsite material would need to be included in the 20 (now 30) work day construction timeline. 28-day strength for concrete can be obtained after substantial completion is declared. Per CDOT Standard Specification 412.22 Opening to Traffic, the roadway can be opened on the concrete sections once the concrete has obtained a compressive strength of 3000 psi. Concrete mix designs shall be used that meet your schedule. In addition, there is an additional five (5) extra days to finish punch list items.

Project working days will be changed from 20 to 30 working days. See Project Special Provision, “Commencement and Completion of Work,” dated September 19, 2018

15. Question: Can traffic control quantities be adjusted and additional days be allowed for road closures be extended to account for: • Potholing? • Concrete pavement curing (28-Day Strength)?

ANSWER: No additional work days will be granted for these items.

Work days will start on the first day of actual work onsite. Items a thru g and items i & j are anticipated to occur before the first day of work onsite. Testing of onsite material would need to be included in the 20 (now 30) work day construction timeline. 28-day strength for concrete can be obtained after substantial completion is declared. Per CDOT Standard Specification 412.22 Opening to Traffic, the roadway can be opened on the concrete sections once the concrete has obtained a compressive strength of 3000 psi. Concrete mix designs shall be used that meet your schedule. In addition, there is an additional five (5) extra days to finish punch list items.

Project working days will be changed from 20 to 30 working days. See Project Special Provision, “Commencement and Completion of Work,” dated September 19, 2018

16. Question: Can the incidental striping scope of work be better explained? • Will there be a double yellow on the centerline of the pavement? • Will there be a solid white along each shoulder?

ANSWER: Pavement striping will be minimal on concrete pavement portions of the project, which includes double yellow centerline and solid white along each shoulder. Lane widths are as designated in the plans.

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17. Question: The following bid items and quantities appear to conflict with one another as shown on the bid schedule and drawings: • Traffic Control Inspection, Bid Schedule = 20-Days, Sheet 5 of the plans = 25- Days. • Erosion Control Management, Bid Schedule = 10-Days, Sheet 16 of the plans = 20-Days.

ANSWER: The construction timeline has been changed to 30 working days and the Traffic Control Inspection bid item has been increased to 30 working days. Erosion Control Management shall be set at 10 days. The bid schedule and plan sheets have been changed to account for these adjustments.

18. Question: Bid Items (212-XXXXX) Revegetation quantities appear to be incorrect since the of limits of disturbance (0.76-AC +/-) includes the road and concrete pavement. Therefore, wouldn’t the seeding, soil conditioning be closer to 0.45- AC? Then would the mulching be less or at least less the quantity of the soil retention blanket?

ANSWER: Bid schedule and plan sheets have been changed to account for the corrected quantities.

19. Question: FYI: On the concrete slope paving; the offsets to the toe wall with a 3:1 side slope don’t take into account the 3-ft wide shoulder, and therefore; the result is a steeper slope on the concrete slope paving at the current roadway centerline offset.

ANSWER: The 6:1 shoulder and the 3:1 slope paving will be the controlling elements and we will adjust elevations as needed in the field to maintain them with direction from the Engineer.

20. Question: Is the contractor responsible for soil, compaction and concrete testing?

ANSWER: Yes.

21. Question: Can we get the complete logs on the potholing previously completed? It would be beneficial to evaluate the elevations on those missing potholes not provided for in the table.

ANSWER: See provided report.

22. Question: The bid item and quantity for “Pipe Removal (And Sleeve)” is misleading. The bid quantity is 254-LF. Either toe wall is roughly 55-LF. The contract documents are more clear, that no waterline lowering are included in

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the contract. Where is the 254-LF of removal taking place exactly? Is this line abandoned?

ANSWER: The waterline is abandoned and it is anticipated that it will need to be removed to complete the rip rap installation.

23. Question: Do you have a list of general contractors bidding this project??

ANSWER: See provided report.

24. See attached Bid Tabulation, Dated September 19, 2018 to reflect changes made from Addendum 1.

25. See attached revisions to the following plan sheets:

• Typical Sections, G-004 (Sheet 4) • General Notes, G-005 (Sheet 5) • Summary of Quantities, G-006 (Sheet6) • Stormwater Management Notes, SW-701 (Sheet 14) • Stormwater Management Notes, SW-703 (Sheet 16) • Stormwater Management Plan, SW-704 (Sheet 17)

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September 19, 2018

Commencement and Completion of Work

The Contractor shall commence work under the Contract on or before the 10th working day following the Contract execution unless such time for beginning the work is changed by the Project Engineer in the "Notice to Proceed." The Contractor shall complete all work (excluding punch list items) within 30 working days in accordance with the "Notice to Proceed" and the punch list items shall be completed within five (5) working days. Work may be temporarily suspended for concrete curing period and cold or inclement weather that would impact the quality of the final work. Only punch list type work can occur during suspension, which will be counted towards the five (5) working day punch list, unless otherwise approved by the engineer. Punch list work shall be done efficiently and effectively so as not to unnecessarily delay work.

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September 19, 2018

Revision of Section 107 Responsibility of Damage Claims, Insurance Types and Coverage

Subsection 107.15 shall be revised to include the following:

County of Boulder, State of Colorado, A Body Corporate and Politic and J-U-B Engineers, Inc. are additional insured as respects general liability and pollution liability. Additional insured shall be endorsed to the policy.

Subsection 107.15 (a) insurance kinds and amounts shall be replaced (when applicable) as follows:

General Liability $1,000,000 Each Occurrence $2,000,000 General Aggregate $2,000,000 Products Completed Operations Aggregate Three (3) year Products/Completed Operations

Excess or Umbrella $3,000,000 Following Form

Automobile Liability $1,000,000 Each Accident *Including Hired & Non-Owned auto

Worker’s Compensation and Employer’s Liability Statutory limits

Pollution Liability $1,000,000 per Loss $1,000,000 Aggregate Coverage maintained or extended discovery for three (3) years.

Note that the above insurance amounts are the minimum required for this project. Proof of current insurance must be provided with your bid in the form of a sample certificate. If you require a waiver of insurance requirements (e.g. Workers’ Comp and sole proprietorships) you may request one in your response with an explanation.

New certificates will be requested if the contract process takes more than 30 days after an award.

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-2- Revision of Section 107 Responsibility of Damage Claims, Insurance Types and Coverage

The Contractor shall provide a Certificate of Insurance to Boulder County demonstrating that the insurance requirements have been met prior to the commencement of Work under this Contract. County of Boulder, State of Colorado, A Body Corporate and Politic and J-U-B Engineers, Inc. are additional insured as respects general liability and pollution liability. Additional insured shall be endorsed to the policy.

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BOULDER COUNTY TRANSPORTATION DEPARTMENT BID # 6888-18 NORTH COUNTY LINE ROAD OVER LITTLE THOMPSON RIVER LOW FLOW CROSSING PROJECT NUMBER: BC-902-LTR; FEMA PROJECT NO. CW-115100C001 BID TABULATION - ADDENDUM #1 19-Sep-2018

ITEM ITEM UNIT TOTAL UNIT TOTAL NO. DESCRIPTION UNITS COST COST 201-00000 Clearing & Grubbing LS 1

202-00035 Pipe Removal (And Sleeve) LF 254

203-00000 Unclassified Excavation CY 314

203-01597 Potholing EACH 4

206-00000 Structure Excavation CY 748

208-00002 Erosion Log (12 Inch) (Biodegradable) LF 70

208-00020 Silt Fence LF 284

208-00045 Concrete Washout Structure EACH 2

208-00070 Vehicle Tracking Pad EACH 2

208-00207 Erosion Control Management DAY 10

210-00810 Reset Delineator EACH 4

210-01000 Reset Fence LF 106

210-04100 Modify pipe EACH 12

211-03005 Dewatering LS 1

212-00003 Mulching (Weed Free) ACRE 0.40 212-00004 Mulching Tackifier ACRE 0.40 212-00006 Seeding (Native) ACRE 0.45 212-00900 Soil Conditioning ACRE 0.45 213-00736 Landscape Boulder (36 inch) EACH 3 214-00299 Cottonwood Tree (10 Gallon Container) EACH 5 214-01015 Willow Cuttings EACH 120 11

BOULDER COUNTY TRANSPORTATION DEPARTMENT BID # 6888-18 NORTH COUNTY LINE ROAD OVER LITTLE THOMPSON RIVER LOW FLOW CROSSING PROJECT NUMBER: BC-902-LTR; FEMA PROJECT NO. CW-115100C001 BID TABULATION - ADDENDUM #1 19-Sep-2018

216-00037 Soil Retention Blanket (Coconut)(Biodegradable) SY 253 304-06000 Aggregate Base Course (Class 6) TON 266 412-00600 Concrete Pavement (9 Inch) SY 883

506-00000 Stockpile Riprap TON 165

506-00412 Buried Riprap (12 Inch) TON 280

506-00424 Buried Riprap (24 Inch) TON 741

601-03000 Concrete Class D CY 120

602-00020 Reinforcing Steel (Epoxy Coated) LB 8822

602-00210 Welded Wire Fabric SY 37

607-11525 Fence (Plastic) LF 300

620-00020 Sanitary Facility EACH 1

625-00000 Construction Survey LS 1

626-00000 Mobilization LS 1

630-00000 Flagging HR 50

630-00007 Traffic Control Inspection DAY 30

630-00012 Traffic Control Management DAY 5

630-80336 Barricade (Type 3 M-B) (Temporary) EACH 4

630-80341 Construction Traffic Sign (Panel Size A) EACH 12

630-80342 Construction Traffic Sign (Panel Size B) EACH 4

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BOULDER COUNTY TRANSPORTATION DEPARTMENT BID # 6888-18 NORTH COUNTY LINE ROAD OVER LITTLE THOMPSON RIVER LOW FLOW CROSSING PROJECT NUMBER: BC-902-LTR; FEMA PROJECT NO. CW-115100C001 BID TABULATION - ADDENDUM #1 19-Sep-2018

FORCE ACCOUNT

700-00010 F.A. Minor Contract Revisions LS 1 700-00020 F.A. Traffic Control LS 1

TOTAL

Enclosed herewith is the required bid bond in the amount of ten percent (10%) ($______) which the bidder agrees to be forfeited to and become the property of the County of Boulder as liquidated damage should this proposal be accepted and a Contract be awarded to him and he fails to enter into a Contract in the form prescribed and to furnish the required bonds and insurance within ten days upon his signing the contract and delivering the approved bonds. In submitting the bid it is understood that the right is reserved by the County of Boulder to reject any and all bids.

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Submittal Instructions:

BIDs are due at the Administrative Services Information Desk or email box (preferred) listed below, for time and date recording on or before 2:00 p.m. Mountain Time on September 25, 2018. A bid opening will be conducted at 3:00 p.m. Mountain Time at county offices.

Your response can be submitted in the following ways. Please note that email responses to this solicitation are preferred, but are limited to a maximum of 25MB capacity. NO ZIP FILES ALLOWED. Electronic Submittals must be received in the email box listed below. Submittals sent to any other box will NOT be forwarded or accepted. This email box is only accessed on the due date of your questions or proposals. Please use the Delivery Receipt option to verify receipt of your email. It is the sole responsibility of the proposer to ensure their documents are received before the deadline specified above. Boulder County does not accept responsibility under any circumstance for delayed or failed email or mailed submittals.

Email [email protected]; identified as BID # 6888-18 in the subject line.

-OR-

US Mail One (1) unbound copy of your submittal, printed double-sided, 11 point, on at least 50% post-consumer, recycled paper must be submitted in a sealed envelope, clearly marked as BID # 6888-18, to the Administrative Services Information Desk located at 1325 Pearl Street, Boulder, CO 80302.

All bids must be received and time and date recorded at the Administrative Services Information Desk by the above due date and time. Sole responsibility rests with the Offeror to see that their bid is received on time at the stated location(s). Any bid received after due date and time will be returned to the bidder. No exceptions will be made.

The Board of County Commissioners reserve the right to reject any and all bids, to waive any informalities or irregularities therein, and to accept the bid that, in the opinion of the Board, is in the best interest of the Board and of the County of Boulder, State of Colorado.

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RECEIPT OF LETTER ACKNOWLEDGMENT

September 19, 2018

Dear Vendor:

This is an acknowledgment of receipt of Addendum #1 for BID #6888-18, North County Line Road Over Little Thompson River Low Flow Crossing.

In an effort to keep you informed, we would appreciate your acknowledgment of receipt of the preceding addendum. Please sign this acknowledgment and email it back to [email protected] as soon as possible. If you have any questions, or problems with transmittal, please call us at 303-441-3525.

Thank you for your cooperation in this matter. This information is time and date sensitive; an immediate response is requested.

Sincerely,

Boulder County Purchasing

Signed by: ______Date: ______

Name of Company______

End of Document

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1835 Weiss Lane Penngrove, Ca 94951

720-863-4576 UTILITY POTHOLING LOG

CUSTOMER JUB Engineering OPERATOR Jesus and Jesus P JOB OR P.O. # TRUCK# 4 LOCATION Co Rd 2 and N 83rd St DATE 11-8-17

1 2 Co Rd 2

Depth Depth to Hard Soft Core Location Pothole # Utility Type Size to Top Bottom Surface Surface Drill Green Pipe 1 Water Main 12" 48" 60" 1 Not Found 7ft deep Electronic depth 8ft 2 Water Main NF NF NF 1 Remarks Contractors Signature______Date 11/8/2017 LOCATES ARE ONLY ACCURATE AT POINT OF POTHOLE The information recorded on this sheet is attended for engineering purposes only. It is recommended that prior to any type of excavation or Directional Boring, utility depths are physically verified. D&M utility Services cannnot and will not be liable for damages to utilities of any type as a result of this documentation. Potholes in concrete and asphalt will be 8 inch core drilled. Excavation will be filled with pea gravel and 4 inches of cold patch at the surface. 1835 Weiss Lane Penngrove, Ca 94951

720-863-4576 UTILITY POTHOLING LOG

CUSTOMER JUB Engineering OPERATOR Jesus and Jesus P JOB OR P.O. # TRUCK# 4 LOCATION N 83rd st and Co Rd 2 DATE 12-1-17

6 5 4 3 2 1

Co Rd 2

Depth Depth to Hard Soft Core Location Pothole # Utility Type Size to Top Bottom Surface Surface Drill Unable to get thru rocks at 8ft Deep 1 Water Main NF NF NF 1 Unable to get thru rocks at 8ft Deep 2 Water Main NF NF NF 1 Hit lots of Ground Water at 30" 3 Water Main NF NF NF 1 Hit lots of Ground Water at 30" 4 Water Main NF NF NF 1 Hit lots of Ground Water at 30" 5 Water Main NF NF NF 1 Steel Casing 6 Water Main 36" 65" 101" 1 Remarks Contractors Signature______Date 12/1/2017 LOCATES ARE ONLY ACCURATE AT POINT OF POTHOLE The information recorded on this sheet is attended for engineering purposes only. It is recommended that prior to any type of excavation or Directional Boring, utility depths are physically verified. D&M utility Services cannnot and will not be liable for damages to utilities of any type as a result of this documentation. Potholes in concrete and asphalt will be 8 inch core drilled. Excavation will be filled with pea gravel and 4 inches of cold patch at the surface.

November 17, 2017

Mr. Jeff Temple, P.E. J-U-B Engineers, Inc. 4745 Boardwalk Dr #200 Fort Collins, Colorado 80525

RE: Final Hydraulic Design of Permanent Repairs for North County Line Road (NCLR) at Little Thompson River [ACE Project No. COJUB14]

Dear Jeff:

This letter report summarizes Anderson Consulting Engineers’ analyses and evaluations supporting the final design of permanent flood repairs at NCLR Low Flow Crossing at Little Thompson River.

INTRODUCTION

The final hydraulic design of permanent repairs to NCLR was developed to mitigate damages caused by the September 2013 Flood and the 2015 Berthoud Tornado. In 2015, the low flow crossing was replaced with six hydraulically equivalent culverts after the existing crossing was destroyed in the Tornado. Proposed repairs include paving the crossing, paving the upstream and downstream approach slopes at the inlet and outlet of the culverts, and providing scour protection at the culvert outlet through rip rap and toe walls. This report documents the hydrologic and hydraulic analyses conducted to support final design.

Background The structure in place before the September 2013 Flood at NCLR consisted of three 64- inch by 43-inch pipe arch culverts. The low flow road crossing was paved above the culverts and on both upstream and downstream slopes. During the September 2013 Flood, the west approach road was washed out (as shown in Figure 1) and later Figure 1 Aerial photo of NCLR low flow crossing post 2013 Flood.

20171117_Final_NCLR_over_Lil_Thomp.docx Page 1 of 7 November 17, 2017 repaired. In June 2015, the Berthoud Tornado passed over the low flow crossing, and combined with flooding from the storm, the low flow crossing culverts were destroyed. Additionally, flooding occurred in May of 2015 which eroded portions of Figure 2 Low flow crossing during spring flooding on May 12, 2015. the approach road as shown in Figure 2.

The interim 2015 emergency repair replaced the previous low flow crossing with six 66-inch by 51-inch pipe arch culverts as shown in Figure 3. Some rock was provided by field crews on the upstream and downstream slopes for erosion protection and was not based on the emergency repair hydraulic analysis. Documentation from emergency repair shows that 120 tons of 12” riprap and 45 tons of 18” riprap was used to protect the banks and upstream and downstream faces of the low flow crossing. The emergency repair design drawings are provided in Attachment A. The emergency repair completed in 2015 was installed by Boulder County maintenance crews. Survey completed for this project in April 2017 by King Surveyors, Inc. shows that the 2015 emergency repair was not installed per the design drawings in Attachment A.

HYDROLOGY

In response to the 2013 Flood, the Colorado Department of Transportation (CDOT), in collaboration with the Colorado Water Conservation Board (CWCB), prepared updated flood frequency information for several river systems along the Front Range. The hydrology for the Big Thompson Watershed was later refined as part of the CHAMP re-study. Appendix D.3 of “Hydrologic Analysis Technical Support Data Notebook for the Big Thompson Watershed” (AECOM, March 2016) provides percent annual change discharges for Little Thompson River 3800 feet downstream of County Road 23E for the 10%, 4%, 2%, 1% and 0.2% of 2,998 cfs, 5,847 cfs, 9,047 cfs, 13,134 cfs, and 24,714 cfs, respectively.

In support of a Figure 3 Downstream side of interim low flow crossing. winter time

20171117_Final_NCLR_over_Lil_Thomp.docx Page 2 of 7 November 17, 2017 construction schedule between October and the end of March of any given year, a low flow discharge probability analysis was performed. The analyses utilized the available mean daily flow data from the Canyon Mouth gage of the Little Thompson River. The results of the analysis provided in Table 1 indicate that from October to March, 10 cfs or less can be expected in the Little Thompson River 97.6% of the time.

Table 1 October to March Discharge Probability of Occurrence at Canyon Mouth Gage (1961-2012).

Cumulative Discharge Occurrences % % Range (cfs) (Days) Occurrence Occurrence 0-1 2355 71.9% 71.9% 1-3 435 13.3% 85.1% 3-5 194 5.9% 91.1% 5-10 213 6.5% 97.6% 10-20 43 1.3% 98.9% 20-30 12 0.4% 99.2% 30-40 9 0.3% 99.5% 40-50 8 0.2% 99.8% 50-70 6 0.2% 99.9% 70-80 2 0.1% 100.0% >80 0 --- Total 3277 100.0%

To assist with summer time construction scheduling, a low flow probability analysis was performed between the months of April and September. The analyses utilized the available mean daily flow data at the Canyon Mouth gage of the Little Thompson River. The results of the summer time low flow probability analysis indicate that from April to September 50 cfs or less can be expected in the Little Thompson River 90% of the time, as presented in Table 2. It is noted that published data available at the Canyon Mouth Gage did not include data for years spanning from 1970 through 1992.

HYDRAULICS

Effective Condition

Upstream of the NCLR Low Flow Crossing at Little Thompson River, the floodplain is regulated by Boulder County. Downstream of the low flow crossing the floodplain is regulated by Larimer County. Both floodplains are FEMA regulated, detailed floodplains. There is no regulatory floodway in Boulder County. Larimer County has a 1-foot regulatory floodway. The Larimer County effective model was obtained and ran to determine the duplicate effective condition. The Boulder County effective model was not available and water surface elevations were summarized from the FIS where applicable. The final design of the low flow crossing will be incorporated into the CHAMP modeling or will be finalized with as-built information after CHAMP becomes the effective model. CHAMP will become the effective model in both Larimer County and Boulder County. Larimer County has accepted CHAMP as the best available data pending incorporation of their review comments into the model. Associated with the CHAMP study is a half-foot floodway.

20171117_Final_NCLR_over_Lil_Thomp.docx Page 3 of 7 November 17, 2017 Table 2 April to September Discharge Probability of Occurrence at Canyon Mouth Gage (1961-2012).

Discharge % Cumulative% Occurrences Range (cfs) Occurrence Occurrence 0-1 1754 34.5% 34.5% 1-3 839 16.5% 51.0% 3-5 325 6.4% 57.4% 5-10 591 11.6% 69.0% 10-20 525 10.3% 79.3% 20-30 251 4.9% 84.3% 30-40 176 3.5% 87.7% 40-50 117 2.3% 90.0% 50-70 163 3.2% 93.2% 70-80 50 1.0% 94.2% >80 294 5.8% 100.0% Total 5085 100.0%

Pre-Project Condition

A pre-project hydraulic model of Little Thompson River at NCLR was developed to establish baseline floodplain and hydraulic conditions for which proposed design improvements are compared. The pre- project condition HEC-RAS hydraulic model developed for this study extends from approximately 1,800 feet downstream of NCLR to 1,100 feet upstream of the low flow crossing. A map showing the location of all model cross sections, floodplains, and floodways is provided in Attachment B.

CHAMP is represented in the current study as the basis of the Pre-Project Condition. The following corrections were made to the CHAMP model geometry LTR_2A_Levee in the Pre-Project Condition based on review of the model:

 The CHAMP model was developed in USACE’s HEC-RAS version 5.0.1, this project utilized HEC-RAS version 5.0.3 due to errors occurring in the floodway run upstream of the culvert crossing (no water surface elevation calculated) and version 5.0.3 being the most up-to-date model.  Cross section 129988 reach lengths of 3335.31, 3393.77, 3174.12 were changed to 354.825, 401.358, 368.333 for the left overbank, channel, and right overbank, respectively, where all reach lengths are in feet.  Contraction and expansion coefficients on the cross sections upstream (129428) and downstream (129328) of the NCLR low flow crossing were changed from 0.1 and 0.3 to 0.3 and 0.5, respectively.  The overtopping weir coefficient for the low flow crossing was changed to provide accurate overtopping discharges where submerged flow occurs (100-year and greater flows).  The culverts were changed from 4.5 foot rise by 6.08 foot span pipe arches to 4.25 foot rise by 5.5 foot span arches. Note that the survey completed for this project listed the culverts as 52” by 43” pipe arch culverts. The culverts were measured in the field by J-U-B engineers and the invoice from the 2015 emergency repair provided in Attachment K confirms that the culverts are 51” by 66” pipe arches.

20171117_Final_NCLR_over_Lil_Thomp.docx Page 4 of 7 November 17, 2017 Detailed, in-channel and structural survey collected by King Surveyors, Inc. in April of 2017, (see Attachment C) was also added to the edited CHAMP model. In-channel survey was added to the following cross sections: 129597, 129428, and 1293228 and the bank stations adjusted accordingly. More detailed ineffective flows were added the surveyed cross sections as well. Reach lengths were adjusted at cross section 129597. The culvert inverts were also updated based on the most recent survey data. Manning’s n values match those utilized in the CHAMP study.

Encroachments in the floodway run were adjusted at cross sections 129998, 129597, 129428, 129328, and 129149 to maintain surcharges between 0.00 and 0.50 feet.

Table 3 summarizes the plan, geometry, and flow files for the various conditions described in this memo.

Table 3 HEC-RAS Model Summary. Geometry Plans Steady Flow File Description File Uses CHAMP Geometry (LTR_2A_Levee) with edits and the survey completed by King Pre-Project Pre- Floodplain_Flows Surveyors in April 2017. Additional detail is Condition Project also provided to model the low flow crossing at NCLR. Pre- Pre-Project 500- Floodplain_Flows Same as Pre-Project Condition Plan but with Project Year _500 Year full cross sections for 500-Year discharge. 500-Year Pre-Project Pre- Same as Pre-Project Condition Plan but for Floodway_Flows Floodway Project floodway analysis. Post Project condition adds the increase in Post Project Post Floodplain_Flows road elevation at the NCLR low flow crossing Condition Project to the existing condition model. Post Post Project 500- Floodplain_Flows Same as Post Project Condition Plan but with Project Year _500 Year full cross sections for 500-Year discharge. 500-Year Post Project Post Same as Post Project Condition Plan but for Floodway_Flows Floodway Project floodway analysis.

Detailed results of the pre-project condition hydraulic analysis and comparisons with all of conditions are provided in Attachment D. Floodplain and floodway comparisons are provided in the maps in Attachment B.

HYDRAULIC DESIGN CRITERIA

The Boulder County Storm Drainage Criteria Manual November 2014 was used to evaluate and design the low flow crossing. According to Section 1002.8 2.A; low water crossings are designed for the initial storm which is defined as a mean annual flood that has a 2.33-year return interval. Based on the Phase II hydrology study, the 2-year discharge calculated from the gage data is 306 cfs. Therefore, a low water crossing design discharge of approximately 350 cfs has been utilized for the current study.

20171117_Final_NCLR_over_Lil_Thomp.docx Page 5 of 7 November 17, 2017 The manual contains Standard Detail SD-10 for a Low Water Crossing. The standard detail references Section 705.6 for sizing riprap at the outlet of the low flow crossing. Section 705.6 provides guidance on riprap sizing at culverts.

Larimer County requires that cross flow structures be designed to a 50-year discharge per Larimer County Rural Area Road Standards Table 6-1. Due to the low flow crossing at NCLR having a small traffic numbers that primarily provides access for local farmers to fields, a lower design discharge has been selected. A variance will be required for the Larimer County approval process and is provided in Attachment H.

HYDRAULIC DESIGN OF IMPROVEMENTS

Post Project Condition Hydraulics

A post project condition hydraulic model was developed to determine potential changes associated with the NCLR low flow crossing permanent repairs relative to the pre-project condition. Proposed design grading along the roadway and the culvert entrance and exit condition changes were used to develop a post project condition hydraulic model.

Detailed post project condition hydraulic modeling results are provided in Attachment D. A digital copy of the HEC-RAS model for all conditions is included with this memo in Attachment G. The proposed hydraulic data for the NCLR low flow crossing at Little Thompson River is summarized in Table 4.

Table 4 Hydraulic Data for the Proposed NCLR Low Flow Crossing at Little Thompson River. Velocity at Recurrence Q Q thru Q Over WSEL Upstream EGL Upstream of Culvert Interval Total Culverts Road of Culverts Culverts Outlet (years) (cfs) (cfs) (cfs) (feet, NAVD88) (feet, NAVD88) (feet/sec) ~2 350 350 0 4.3 5088.16 5088.3 10 2,998 917 2,081 8.3 5094.37 5094.55 25 5,847 832 5,015 7.6 5095.89 5096.19 50 9,047 808 8,239 7.3 5096.79 5097.24 100 13,134 707 12,427 6.4 5096.89 5097.81 500 26,665 152 26,513 1.4 5098.58 5098.70

Responses to Boulder County review comments for the 30% FIR Hydraulics submittal and 90% FOR Hydraulics submittal are provided in Attachment J.

Erosion Protection

Hydraulic parameters determined in the proposed condition model were used to determine erosion protection at the culvert outlet and for road overtopping. Riprap protection at the culvert outlets was calculated according to Boulder County Storm Drainage Criteria Manual Section 705.6. Excerpts and calculations are provided in Attachment I. The recommended riprap size for outlet protection is D50 of 12 inches for 21 feet downstream of the culvert.

20171117_Final_NCLR_over_Lil_Thomp.docx Page 6 of 7 November 17, 2017

LCR #2

N

0 20 40

SCALE IN FEET LITTLE THOMPSON RIVER THOMPSON LITTLE HORZ 0 20 40

VERT 0 5 10 SCALE IN FEET EFFECTIVE LEGEND PRE-PROJECT

ATT NCLR LOW FLOW CROSSING ATTACHMENT B.1 AT LITTLE THOMPSON RIVER EFFECTIVE AND BOULDER COUNTY PRE-PROJECT FLOODPLAIN Anderson Consulting Engineers, Inc Civil ▪ Water Resources ▪ Environmental B.1 375 East Horsetooth Road, Building 5, Fort Collins, CO 80525 CROSS SECTION LOCATION AND FLOODWAY Phone (970) 226-0120 / Fax (970) 226-0121 www.acewater.com MAP COMPARISON PRE-PROJECT LEGEND POST PROJECT

ATT NCLR LOW FLOW CROSSING ATTACHMENT B.2 AT LITTLE THOMPSON RIVER PRE-PROJECT AND POST BOULDER COUNTY Anderson Consulting Engineers, Inc Civil ▪ Water Resources ▪ Environmental B.2 PROJECT FLOODPLAIN AND 375 East Horsetooth Road, Building 5, Fort Collins, CO 80525 CROSS SECTION LOCATION Phone (970) 226-0120 / Fax (970) 226-0121 FLOODWAY COMPARISON www.acewater.com MAP

phone: (970) 686-5011 | fax: (970) 686-5821 (970) fax: | 686-5011 (970) phone:

650 E. Garden Drive | Windsor, Colorado 80550 Colorado Windsor, | Drive Garden E. 650

K S

URVEYORS

ING 1

RIVER LITTLE THOMPSON LITTLE

Of

TOPOGRAPHIC SURVEY

LCR 2 & LITTLE THOMPSON 2 ROAD COUNTY LARIMER LEGEND TABLE D1: BASE FLOOD ELEVATIONS COMPARISON TABLE Project Name : Hydraulic Analysis for North County Line Road Low Flow Crossing at Little Thompson River Company: Anderson Consulting Engineers Inc. Completed By: Wendy Banzhof, Engineer II FLOODING SOURCE(S): Little Thompson River: Main Channel COMMUNITY(IES): Boulder County, Larimer County SOURCE DATA COMPARISONS HYDRAULIC CROSS-SECTION INFO. 100-YEAR BASE FLOOD ELEVATIONS (NAVD88) Duplicate Pre- Post Dup. Pre Post Project Effective Duplicate Pre- Post Pre-Project Post Project Effective Project Project Pre- Post Eff. Project Fldwy. Cross- Effective Effective Project Project Fldwy. vs. vs. (Ayers) Stream Stream Stream Project Project vs. vs. vs. Section ID (Ayres) Floodway Floodway Pre-Project Pre-Project Station Station Station Eff. Ayres Post Project 120500 -- 130497 130497 5104.8 -- 5102.75 5102.76 5102.75 5102.76 -- -- 0.01 0.00 0.01 -- 111909 129998 129998 -- 5099.0 5099.11 5099.11 5099.11 5099.11 -- 0.1 0.00 0.00 0.00 -- 111501 129597 129597 -- 5096.6 5098.23 5098.27 5098.22 5098.27 -- 1.6 0.04 -0.01 0.05 119050 111250 129428 129428 5094.4 5096.3 5096.90 5097.05 5096.89 5097.06 1.9 0.6 0.15 -0.01 0.17 North County Line Road Low Flow Crossing North County Line Road Low Flow Crossing North County Line Road Low Flow Crossing AJ 111200 129328 129328 5093.4 5093.4 5096.11 5096.12 5096.11 5096.12 0.0 2.8 0.01 0.00 0.01 -- 110866 129149 129149 -- 5091.4 5094.57 5094.58 5094.57 5094.58 -- 3.2 0.01 0.00 0.01 -- = Not applicable or no direct comparison available Boulder County effective HEC2 model

\\diskstation\projects\COJUB14_NCLR_over_Lil_Thomp_Final_Des\Spreads\Comparison Tables09042017.xls .

TRANSPORTATION DEPARTMENT OFFICE USE th :Boulder CO 80304 Floodplain Permit Number ۰ 13 2525 :PO Box 471 ۰ Boulder CO 80306 Building Permit Number Phone: 303-441-3900 Docket Number: Fax: 303-441-4594 Fee Paid: YES NO NOT REQUIRED Approved: YES NO Effective Date:

FLOODPLAIN DEVELOPMENT PERMIT AND APPLICATION FORM

OWNER AND PROPERTY INFORMATION Applicant/Owner Name: Phone:

Address: Fax:

City: State: Zip:

Engineer/Contractor Name: Phone:

Address: Fax:

City: State: Zip:

PROJECT INFORMATION

Location of Development: City:

Section/Township/Range:

Proposed Project: new structure addition remodel mobile home

attached garage accessory structure fill excavation change of use

Other (describe):

Description of Development:

SUBMITTAL REQUIREMENTS (check items included with application)

Construction and Material Specification Location Map (2000’ scale U.S.G.S topo)

Development Plan (stamped by Colorado Registered Professional Engineer)

REMODELS AND REDEVELOPMENT ONLY

Cost of Improvement for this project: (submit itemized cost list, or projected appraised value upon completion)

Value of Structure: (submit current (within 1 year) appraiser’s valuation of structure)

Cumulative value of improvements:

Substantial Improvement: Yes No (Yes, if cost of project ≥ 50% of appraised valuation)

If no, have other improvements been made to the structure since Nov 1, 1991? Yes No

Cumulative Value of all improvements:

Substantial Improvement: Yes No (Yes, if costs of all improvements since Nov 1, 1991 ≥ 50% of appraised valuation)

- 1 - Floodplain Development Permit and Application Form

FLOODPLAIN INFORMATION

Note to Applicants: Fill out as much information as possible. Please refer to Land Use documents for approval conditions for base flood elevation and flood protection elevation. If you have questions, or need assistance filling out this form, contact the Boulder County Transportation Department.

Floodplain Name: Station No.

FEMA Flood Zone Designation A AE AO X (shaded) X (unshaded)

Base Flood Elevation: NGVD (29) NAVD (88)

Flood Protection Elevation: NGVD (29) NAVD (88)

Floodway: Yes No (If yes, please submit Engineers report addressing those standards set forth in Article 4-407)

Title Report Floodway Analysis Permit Advertised Cross Sections

Description of extent to which water course will be altered

USE ONLY OFFICE

REGULATORY REQUIREMENTS

Structure is: elevated floodproofed vented n/a

Elevation Certificate: Yes No

If floodproofed, describe method:

Lowest floor elevation: NGVD (29) NAVD (88)

Elevation of garage slab: NGVD (29) NAVD (88)

Lowest elevation of HVAC equipment: NGVD (29) NAVD (88) (and other mechanical equipment)

Enclosed area (not floodproofed or elevated) square feet

Number of vents: Area of vents: square inches

FOR STRUCTURES: Attach building plans showing foundation design, flood elevation, floor elevations, HVAC and other mechanical equipment elevations, size and location of vents, floodproofing design and other relevant information that address those standards set forth in Article 4-407.

FOR SITE WORK: Attach site and grading plans and other relevant information. All plans must be stamped and signed by a Colorado Registered Professional Engineer

Certification: I certify that the above information is correct and agree to construct this building in accordance with the plat, building plans and specifications submitted, and in strict compliance with all the provisions of the Zoning Ordinance, Building Code, and Health and Plumbing Regulations of Boulder County.

Signature of applicant: Date:

Printed name:

Signature of floodplain Date: administrator:

Comments:

- 2 - Flood Plain Development Permit

Permit Number Date

Owner Phone

Address

Contractor Phone

Address

Project Address/Location

Project Description

Single Family Residence New Construction Channelization Fill

Multi-Family Residence Improvement >50% Bridge/Culvert Levee

Manufactured Home Improvement <50% Rehabilitation Other

Commercial

Explanation:

Flood Hazard Data

Watercourse Name

The project is in the Floodway . The project is in the Flood Fringe

The 100 year base flood elevation for the project is

Lowest Floor Protection Elevation required add 1.5 feet

Flood Proofing Elevation required

Source Documents: Reports/Maps used Proposal Review Checklist

Site development plans are complete and depict flood hazard data

Engineering data is provided for proposed map and floodway revisions

Floodway certificate and data document no increase in flood heights

Subdivision proposals minimize flood damage and protect utilities

Lowest floor elevations are at or above the 100 year base flood elevation

Manufactured homes address elevation and anchoring requirements

A flood proofing certificate has been submitted

Other:

Permit Action and Compliance Documentation

Permit Approved : The proposed project was reviewed and is in compliance with flood plain management standards as established by FEMA and Larimer County

Permit Denied : The project was denied and information is in Flood Review Board files

Variance Granted : A variance to the 100 year base flood elevation was granted and information is in Flood Review Board files

Variance Granted : A variance was granted from the Code for all or part of the 18 inch lowest floor protection elevation

Elevation Certificate : A certificate was returned before a certificate of occupancy was issued

Flood Proofing Certificate : Certification was returned before a certificate of occupancy was issued

Permit Closure:

County Floodplain Official’s Signature Date

Comments:

Attachment I Hydraulic Toolbox Riprap Analysis for Embankment Overtopping/Channel Slopes >2%

Input Result Additional Considerations Discharge/ Total Embankment Change in Water Surface Recurrence Discharge Overtopping Embankment Upstream to Downstream of Interval (cfs) Length (ft) Slope (_H:1V) D50 Weir 1000 cfs 82 65 1 9.5 2.74 1500 cfs 547 153 2 21.5 2.97 2000 cfs 1057 205 2 21.5 2.9 2000 cfs 1057 205 4 12.5 2.9 10-Year 2081 258 3 44.5 2.69 10-Year 2081 258 4 15.5 2.69 100-Year* 12427 592 4 31.5 0.78 *Protected by tailwater that is not considered in these calculations.

Attachment J: Boulder County Hydraulics Review Comments and Resonses Review Comment Sheet Project Name: North County Line Road at Little Thompson River 30% Submittal

Item Number Comment (Boulder County) Response/Comment (ACE) Please reference in the report what version of HEC-RAS was used for the A note has been provided in the hydraulics hydraulic modeling. section of the report under the corrected 1 effective condition. HEC-RAS version 5.0.3 was utilized for this project.

In the submitted report, Table D1, Base Flood Elevations Comparison Table has Spelling has been corrected. 2 “Ayers” spelled incorrectly. The correct spelling should be “Ayres." Please correct the spelling. The inlet and outlet elevations provided do not seem to match. On the Culvert inlet and outlet elevations have been submitted plans, the inlets are shown to be 5085.2 and outlets to be 5084.8. The reviewed. The Proposed and Existing submitted HY8 shows the inlets to be 5085.5 and the outlets to be 5085.0. The condition models use inlets from King submitted HEC-RAS model survey shows Inlets range from 5103.3 to 5104.5 and Surveyor's survey. The Corrected Effective outlets range from 5102.9 to 5103.4. Please review and make any necessary condition uses inlet and outlet elevations 3 changes. from the CHAMP model. The HY8 analysis is not applicable for this project and has been removed from the documentation to avoid confusion.

In the proposed conditions plan the culvert at river station 129387 shows a weir The HEC-RAS model has been adjusted to flow over the road of 28,403.66 cfs. Please review the computations for the reach a stable solultion. 4 culvert so the total flow does not exceed the total 100-yr discharge. Comparing the HY8 Post project 100-yr water surface elevation (5103.92) to the The HY8 run was provided as a reference for HEC-RAS computed Headwater elevation (5096.49) there is over a 7 foot the previously completed emergency difference. Although there are some slight differences in the invert elevations repairs. It was utilized to determine between the two models the large discrepancy is probably not caused by a 0.3’ equivalent hydraulic sizes for the emergency 5 difference in the invert elevation of the culverts. Please review and provide an repair culverts. As such it is not part of the explanation or make any necessary changes. current project and has not been utilized for comparison purposes. The documentation has been removed to avoid confusion. Attachment J: Boulder County Hydraulics Review Comments and Resonses Review Comment Sheet

Project Name: North County Line Road at Little Thompson River 90 % Submittal

Item Number Comment (Boulder County) Response/Comment (ACE) The King Surveyor's AutoCad file has been Please submit the digital surface and AutoCAD file for the King Survey with the 1 included in Attachment C, the digital surface final submittal. is included in this file. The culverts used in the 90% HEC-RAS model Sheet 4 of the plans and the King survey show existing culverts to be 6- 52” x 68” were left as modeled in the CHAMP model. (a 60” round equivalent) CMP. The report says 6-64” x 43” pipe arch culverts The culvert sizes summarized in the report exist (this is a 54” round equivalent). The HEC-RAS model shows 6-54” x 73” were those used in the emergency repair CMPA. Standard sizes vary depending on the size of the culvert corrugation. analysis. Due to the discrepencies between From the survey dimensions it appears likely that the actual culvert size that theses sources, JUB remeasured the culverts matches standard arch pipe sizes would be a 66” x 51”. This is the arch pipe and noted the stamps on the culverts in the made from a 60” round with 3”x1” corrugations. This could easily be measured field. JUB measured the culverts as a 66" x in the field +/- 2” due to the corrugations. Here is a reference to a table showing 51" with 3" x 1" corrugations, stamped June standard size arch pipes. http://www.txcorr.com/wp- 2014. The corresponding Boulder County 2 content/uploads/2014/10/CMP-DETAIL-SHEET2.pdf invoice lists the pipes as 60" RD EQ (66x51) Spot Welded Arched. The HEC-RAS model The culverts should be shown in the culvert data editor using the “Arch” shape has been updated as recommended. The with the dimensions of rise = 4.25’ (51”) and a span = 5.5’ (66”) and the report plans have also been updated to match the text corrected to note that the surveyed size was corrected to match the actual pipe sizes. Boulder County's invoice is standard size or an explanation of the culvert size determination. (note that provided as Attachment K. with the 66 x 51 size the culvert flow information changes but the WSEL upstream of the culverts does not change due to the effect of the very high backwater downstream of the crossing)

Cross sections 129597 and 129428 cross. Cross sections are not allowed to cross The GIS coordinates in the HEC-RAS model 3 in HEC-RAS. Please make corrections necessary to resolve this issue. have been corrected to not cross and match the workmap. The Coefficients of contraction and expansion (Cc, Ce) should be set to 0.3 and 4 0.5 respectively at cross section 129597 per HEC-RAS guidance. Please correct or explain why this setting should stay as 0.1 and 0.3 respectively. The coefficents have been corrected to be 0.3 and 0.5.

12/30/2015 FEDERAL EMERGENCY MANAGEMENT AGENCY REC-01 21:25:01 RECORD OF ENVIRONMENTAL CONSIDERATION (REC)

Project ID: PA-08-CO-4229-PW-00164 Title: BL001 - Damaged County Roads

NEPA DETERMINATION

Non Compliant Flag: No EA Draft Date: EA Final Date: EA Public Notice Date: EA Fonsi Date: Level: CATEX EIS Notice of Intent Date: EIS ROD Date: Comments: CAT C. 50.0% complete. Work includes repairs to 6 county roads within Boulder County. Work includes replacement of road base material, washed out shoulders, eroded riprap, road embankment wash out, separated concrete capping from CMPs, replacement of CMPs, replacement of flexible lane delineators and concrete aprons. All sites are back to pre-disaster condition and/or upgrading to current codes and standards except the hazard mitigation for Site 1. All sites were reviewed for mitigation opportunities. Site 1 was deemed cost effective and technically feasible for HMP The HMP for Site 1 recommends the addition of 3 more 60x56 CMPs (to add to the existing 3 60x56 CMPs) to help convey water under a low water crossing to prevent the low water crossing from washing out in future events. The applicant has provided an H&H and No-Rise Certificate showing no adverse impact. Lat-long of sites: Site 1 - North County Line Rd (40.26114, -105.15491) Site 2 - North 66th St and Highland Ditch (40.208203, -105.19928/40.205039, -105.19929) Site 3 - Hygiene Rd (40.188941, -105.2489/40.188953, -105.24981; 40.188931, -105.24478/40.199933, -105.24311) Site 4 - North 51st Street (40.157218, -105.23505; 40.159580, -105.235316/40.157218/-105.235053; 40.156027, -105.235064/40.154530, -105.235119) Site 5 - Upper Four Mile Canyon Rd (40.03938, -105.39302/40.03909, -105.39361) Site 6 - North 83rd St at Little Thompson Creek (40.257608, -105.15924)

- erobert6 - 12/28/2015 19:12:41 GMT

CATEX CATEGORIES

Catex Category Code Description Selected xv (xv) Repair, reconstruction, restoration, elevation, retrofitting, upgrading to Yes current codes and standards, or replacement of any facility in a manner that substantially conforms to the preexisting design, function, and location;

xvi (xvi) Improvements to existing facilities and the construction of small scale Yes hazard mitigation measures in existing developed areas with substantially completed infrastructure, when the immediate project area has already been disturbed, and when those actions do not alter basic functions, do not exceed capacity of other system components, or modify intended land use; provided the operation of the completed project will not, of itself, have an adverse effect on the quality of the human environment;

EXTRAORDINARY CIRCUMSTANCES

Extraordinary Circumstance Code Description Selected ? No Extraordinary Circumstances were selected

ENVIRONMENTAL LAW / EXECUTIVE ORDER

Environmental Law/ Executive Order Status Description Comments

NOTE: All times are GMT using a 24-hour clock. Page 1 of 6

12/30/2015 FEDERAL EMERGENCY MANAGEMENT AGENCY REC-01 21:25:01 RECORD OF ENVIRONMENTAL CONSIDERATION (REC)

Project ID: PA-08-CO-4229-PW-00164 Title: BL001 - Damaged County Roads

Environmental Law/ Executive Order Status Description Comments Clean Air Act (CAA) Completed Project will not result in permanent air emissions - Review concluded

Coastal Barrier Resources Act Not Project is not on or connected to CBRA Unit (CBRA) Applicable or otherwise protected area - Review concluded

Clean Water Act (CWA) Completed Project would affect waters, including Boulder Countys Transportation Flood Recovery wetlands, of the U.S. Coordinator stated prior to work listed under work to be completed on Site 1 all appropriate permits will be obtained. Project activities have the potential to impact Waters of the United States or wetlands. Project involves dredge, fill, excavation and/or modification. - erobert6 - 12/28/2015 19:23:13 GMT

Completed Project may require Section 404/401 or Section 9/10 (Rivers and Harbors Act) permit, including qualification under Nationwide Permits - Review concluded

Coastal Zone Management Act Completed Project is not located in a coastal zone area (CZMA) and does not affect a coastal zone area - Review concluded

Executive Order 11988 - Completed Located in floodplain or effects on Project is located within Site 1 Zone AE, FIRM Floodplains floodplain/flood levels panel 08013C0125J, dated 12/18/2012. The Project has the potential to impact floodplains. See EO Checklist attached. Project is located in Site 5 Zone AE, FIRM panel 08013C0370J, dated 12/18/2012 and Site 6 Zone AE, FIRM panel 08069C1368G, dated 02/06/2013. Per 44 CFR Part 9.6 Step 1: Project repairs are determined to have no effect on floodplain or wetlands provided that the repairs remain in the existing footprint and do not impact previously undisturbed areas. No further floodplain review is required. Project is located in Site 2 Zone X, FIRM panel 08013C0254J, dated 12/18/2012, Site 3 Zone X FIRM panel 08013C0253J, dated 12/18/2012 and Site 4 Zone X FIRM panel 08013C0265J, dated 12/18/2012. - erobert6 - 12/28/2015 19:32:19 GMT

Completed Possible adverse effects associated with investment in floodplain, occupancy or modification of floodplain environment

Completed 8 Step Process Complete - documentation attached - Review concluded

NOTE: All times are GMT using a 24-hour clock. Page 2 of 6

12/30/2015 FEDERAL EMERGENCY MANAGEMENT AGENCY REC-01 21:25:01 RECORD OF ENVIRONMENTAL CONSIDERATION (REC)

Project ID: PA-08-CO-4229-PW-00164 Title: BL001 - Damaged County Roads

Environmental Law/ Executive Order Status Description Comments Executive Order 11990 - Completed No effects on wetlands and project outside Project site work is not in a mapped wetland. - Wetlands wetlands - Review concluded erobert6 - 12/28/2015 19:32:53 GMT

Executive Order 12898 - Completed Low income or minority population in or near The entire community will benefit from the Environmental Justice for Low project area completion of this project. - erobert6 - Income and Minority Populations 12/28/2015 19:33:17 GMT

Completed No disproportionately high and adverse impact on low income or minority population - Review concluded

Endangered Species Act (ESA) Completed Listed species and/or designated critical Re: Prebles Meadow Jumping Mouse and Ute habitat present in areas affected directly or ladies tresses: The scope of work has been indirectly by the federal action reviewed and meets the May Affect, Not Likely to Adversely Affect criteria (Table 3, Item 7, 9, 14, 42) outlined in the 2015 DR-4229-CO Programmatic Consultation Agreement signed by FEMA and the USFWS. The project returns the damaged facility to pre-flood function, location and capacity; access is through previously disturbed areas or uses a route that avoids destruction of live or dormant vegetation; and, project disturbance is limited to areas devoid of vegetation resulting from Disaster- related disturbance. See Conditions for Conservations Measures that must be implemented for projects to qualify as NLAA under the DR-4229-CO Programmatic Consultation Agreement signed by FEMA and the USFWS on 11/09/15. The scope of work that consists of repairing or replacing road surface has been reviewed and meets the No Effect criteria (Table X, Item 25) outlined in the DR-4229-CO Programmatic Consultation Agreement signed by FEMA and the USFWS on 11/09/15. - erobert6 - 12/28/2015 19:15:19 GMT

Completed May affect, but not likely to adversely affect species or designated critical habitat (FEMA determination/USFWS/NMFS concurrence attached) - Review concluded

Farmland Protection Policy Act Completed Project does not affect designated prime or (FPPA) unique farmland - Review concluded

Fish and Wildlife Coordination Completed Project does not affect, control, or modify a Act (FWCA) waterway/body of water - Review concluded

Migratory Bird Treaty Act (MBTA) Completed Project located within a flyway zone

NOTE: All times are GMT using a 24-hour clock. Page 3 of 6

12/30/2015 FEDERAL EMERGENCY MANAGEMENT AGENCY REC-01 21:25:01 RECORD OF ENVIRONMENTAL CONSIDERATION (REC)

Project ID: PA-08-CO-4229-PW-00164 Title: BL001 - Damaged County Roads

Environmental Law/ Executive Order Status Description Comments Completed Project does not have potential to take migratory birds - Review concluded

Magnuson-Stevens Fishery Completed Project not located in or near Essential Fish Conservation and Management Habitat - Review concluded Act (MSA)

National Historic Preservation Act Completed Applicable executed Programmatic The scope of work has been reviewed and (NHPA) Agreement. Activity meets Programmatic meets the criteria of the September, 24, 2014 Allowance (enter date and # in comments) - signed Programmatic Agreement Item II; Section Review concluded C. 1. c (culverts), Item II; Section C. 1. a (roads to pre-disaster design & to meet current codes and standards), Item I; Section C. 1. d (re- establishment of existing roadway ditches), ), Item I; Section C. 1. f (installation/removal of temp traffic control devices) agreed to by FEMA and the SHPO. - erobert6 - 12/28/2015 19:14:21 GMT

State Hazardous Materials and Completed Review concluded Work involves removal, staging, transporting, Solid Waste Laws and/or disposal of debris. (Includes culverts) Note: Applicant states - the vegetative debris from Site 6 was placed on-site, outside the floodplain and that the salvaged concrete and culverts at Site 1 were hauled to a Boulder Countys Transportation Department maintenance yard. - erobert6 - 12/28/2015 19:26:33 GMTNote: Concrete material was hauled to the Boulder County yard at Walden Ponds (3897 North 75th street, Boulder, CO; 40.042774, -105.185637). It has or will be crushed and recycled/ reused. The steel culverts were taken to the same location, crushed and placed in a steel recycling dumpster. When our recycling dumpsters are full they are hauled, and the materials recycled, by Western Metals Recycling (2100 West Oxford Ave., Englewood, CO; 39.639927, -105.01392). - erobert6 - 12/30/2015 18:12:55 GMT

Wild and Scenic Rivers Act Completed Project is not along and does not affect Wild (WSR) and Scenic River - Review concluded

CONDITIONS

Special Conditions required on implementation of Projects: Applicant is responsible for coordinating with the local floodplain manager and obtaining and complying with all required permits and permitting conditions. All required permits should be maintained as part of the permanent record. Source of condition: Executive Order 11988 - Floodplains Monitoring Required: No

NOTE: All times are GMT using a 24-hour clock. Page 4 of 6

12/30/2015 FEDERAL EMERGENCY MANAGEMENT AGENCY REC-01 21:25:01 RECORD OF ENVIRONMENTAL CONSIDERATION (REC)

Project ID: PA-08-CO-4229-PW-00164 Title: BL001 - Damaged County Roads

For Work Not Completed: The applicant is responsible for verifying and compliance with all permit requirements, including permit conditions, pre-construction notification requirements and regional conditions as provided by the US Army Corps of Engineers (USACE). The applicant is responsible for implementing, monitoring, and maintaining all Best Management Practices (BMPs) and Pre-Construction Notification (PCN) conditions of applicable Nation Wide Permits (NWP). This is to include any requirements per the Colorado Department of Public Health and Environment 401 Water Quality Certification for Clean Water Act permits.

Source of condition: Clean Water Act (CWA) Monitoring Required: No

a. Design the project to avoid and minimize permanent and temporary impacts to riparian and adjacent upland habitats. b. Avoid or minimize the amount of concrete, riprap, bridge footings, and other hard, impermeable engineering features within the stream channel and riparian or adjacent upland habitats. If riprap is used, bury the riprap then plant with native riparian vegetation where technically feasible. c. Where technically feasible, use bioengineering techniques to stabilize stream banks when stabilization of natural banks is needed. d. Minimize the number and footprint of access routes, staging areas, and work areas. e. Locate access routes, staging areas, and work areas within previously disturbed or modified non-habitat areas. f. Install limits of work fencing (e.g., orange barrier netting or silt fencing), signage, or other visible markers to delineate access routes and the project area from habitats. Use this fencing to enforce no-entry zones. g. Hold a preconstruction briefing for onsite personnel to explain the limits of work and other conservation measures. h. Follow regional stormwater guidelines and design best management practices (BMPs) to control contamination, erosion, and sedimentation, such as silt fences, silt basins, gravel bags, and other controls needed to stabilize soils in denuded or graded areas, during and after construction. i. Locate utilities along existing road corridors, and if possible, within the roadway or road shoulder. i.Bury overhead utilities whenever possible. ii.Directionally bore utilities and pipes underneath habitats whenever possible. j. Develop and implement a habitat restoration plan that addresses site preparation, planting techniques, control of non-native weeds, and use of native seed mixtures (see Appendix B). k. Contact USFWS immediately by telephone at (303) 2364773 if a Prebles is found alive, dead, injured, or hibernating within the project area. Contact the Service if any other listed species are found within the project area. l. To the maximum extent practicable, limit disturbing (e.g., crushing, trampling) or removing (e.g., cutting, clearing) all vegetation, such as willows, trees, shrubs, and grasses within riparian and adjacent upland habitats. i.Restrict the temporary or permanent removal of vegetation to the footprint of the project area. ii.Minimize the use of heavy machinery and use smaller equipment when possible. iii.Soil compaction: Temporarily line access routes with geotextiles or other materials, especially in wet, unstable soils to protect roots and the seed bank. m. Locate, store, stage, operate, and refuel equipment outside of riparian or adjacent upland habitats. n. During the Prebles active season (May 1 through November 1), work only during daylight hours to avoid disrupting Prebles nocturnal activities. o. Promptly remove waste to minimize site disturbance and avoid attracting predators. p. Use BMPs to limit construction-related disturbance, such as soil compaction, erosion, and sedimentation, and to prevent the spread of invasive weeds; i. Soil compaction: Establish one access route for workers, vehicles, and machinery, preferably along a previously disturbed surface or route. ii.Soil compaction: Temporarily line access routes with geotextiles or other materials, especially in wet, unstable soils. iii.Weed control: Wash and inspect vehicles and equipment before entering or leaving the project area so that they are free of noxious weed seeds and plant parts. iv.Weed control: Use only weed free certified materials, including gravel, sand, top soil, seed, and mulch. q. Upon project completion, revegetate all disturbed areas with native shrubs, trees, and grasses. Use only weed free material and native seed mixtures recommended by USFWS. r. Identify conservation measures that were implemented to avoid and minimize potential impacts.

Source of condition: Endangered Species Act (ESA) Monitoring Required: No

Gravel/borrow materials for work to be completed must be obtained from one of the following pre-approved sources: (FEMA/SHPO approved source, CO Licensed Pit, commercial source, contractor or county Stockpiles). Source of condition: National Historic Preservation Act (NHPA) Monitoring Required: No

Debris must be appropriately separated and disposed of in an approved disposal site or landfill. Asphalt must be recycled as a blended base material or appropriately separated and disposed of in an approved disposal site or landfill in accordance with the CDPHE authorized waste management regulations.

Source of condition: State Hazardous Materials and Solid Waste Laws Monitoring Required: No

NOTE: All times are GMT using a 24-hour clock. Page 5 of 6

12/30/2015 FEDERAL EMERGENCY MANAGEMENT AGENCY REC-01 21:25:01 RECORD OF ENVIRONMENTAL CONSIDERATION (REC)

Project ID: PA-08-CO-4229-PW-00164 Title: BL001 - Damaged County Roads

This PW as written is for return to pre-disaster form and function. If at any point in the future the applicant would like to adjust the scope of work to perform mitigation or improvement the entire scope of work must be submitted to EHP for review.

Source of condition: NEPA Determination Monitoring Required: No

Standard Conditions: Any change to the approved scope of work will require re-evaluation for compliance with NEPA and other Laws and Executive Orders.

This review does not address all federal, state and local requirements. Acceptance of federal funding requires recipient to comply with all federal, state and local laws. Failure to obtain all appropriate federal, state and local environmental permits and clearances may jeopardize federal funding.

If ground disturbing activities occur during construction, applicant will monitor ground disturbance and if any potential archeological resources are discovered, will immediately cease construction in that area and notify the State and FEMA.

NOTE: All times are GMT using a 24-hour clock. Page 6 of 6

3823 Winona Court AUCKLAND ENVIRONMENTAL CONSULTING Denver, Colorado 80212

Wetlands Ÿ Wildlife Ÿ Vegetation 303-358-2687 [email protected]

Technical Memorandum ______

To: Mr. Jeff Temple, Project Manager, J-U-B Engineers Inc. Ms. Kristine Obendorf, Project Manager, Boulder County Transportation

Date: January 11, 2018

Re: Fish Passage Improvements, North County Line Road Low Water Crossing of the Little Thompson River, Boulder and Larimer Counties, Colorado ______

1.0 Introduction Boulder County Transportation (County) plans to repair the North County Line Road low water crossing of the Little Thompson River (project) (Boulder County Project Number BC-902-LTR) due to damage caused by flooding in May 2015. The repairs are being reimbursed by the Federal Emergency Management Agency (FEMA) (FEMA Project No. CW-115100C001). The County has retained J-U-B Engineers, Inc. (J-U-B) to design the project. J-U-B has subcontracted with Anderson Consulting Engineers (ACE) to analyze hydraulics and with Auckland Environmental Consulting (Auckland) to complete environmental documentation and permitting. This memo has been prepared to summarize steps taken to improve fish passage.

2.0 Project Description Within the project area, the Little Thompson River (river) channel is approximately fifty feet wide with a fairly flat, gravel bottom. During most of the year, water only partially fills the channel and the average depth is approximately five inches. During high flows, the channel is full and the average water depth is approximately 16 inches. The channel is almost dry during the lowest flows, typically in the winter.

The existing crossing consists of six 60-inch equivalent (51” X 66”) culverts covered with riprap. Each culvert is 60-feet long. This crossing was installed by Boulder County road maintenance in the fall of 2015 after the previous low flow crossing was washed out by high flows. In order to reduce the likelihood of the crossing washing out again, FEMA is providing hazard mitigation funding to stabilize the crossing. Based on design and budget constraints, the existing culverts will remain in place and be stabilized with riprap and concrete.

TECHNICAL MEMORANDUM JANUARY 11, 2018 NORTH COUNTY LINE ROAD FISH PASSAGE PAGE 2 OF 4

3.0 Methods Three possible impediments to fish passage were evaluated; physical barriers, shallow water, and high flow velocities. During conceptual design, the project team evaluated whether the existing crossing is a barrier to fish passage. Water depth and velocity was estimated by ACE, based on a peak flow gage analysis done as part of the post-2013 flood hydrologic studies. Auckland reviewed data on minimum water depths and maximum flow velocity for fish passage. Once the design team decided to leave the existing culverts in the place, the preliminary plans were reviewed for ways to improve fish passage.

4.0 Results

4.1 Design Review The existing culverts were installed flush with the river bottom and do not block fish passage. The channel at the crossing is wider than in other areas, thus creating shallow water that could limit fish passage during low flows. However, this has been mostly offset by natural development of low flow channels with similar depths to those upstream and downstream of the crossing. A concrete apron to be installed on the south/upstream side of the crossing could potentially block fish passage (see below for design modifications).

4.2 Hydrologic Data River flow fluctuates significantly throughout the year. Thus, ACE estimated average water depth and flow velocity based on four flow rates (Table 1). However, it is important to consider that the data in Table 1 are averages. The actual water depth and velocity vary significantly within the channel. Water is slightly deeper along the thalweg and much deeper in pools. Velocity is greatest in the channel center and decreases closer to the sides and bottom of the river. Within culverts, water also moves more slowly closer to the sides and bottom. Rocks, logs, and other features also slow the water.

Table 1. Little Thompson River Estimated Average Flow Data Flow rate Velocity Water Depth Flow Description (Cubic feet per (Feet per (Inches) second) second) Ordinary Low Flow Negligible Close to zero Not applicable (Lowest ~1-3 months per year, typically in winter) Ordinary Flow 20 cfs 4.8” 2.2 ft/sec (Typical volume, ~6-9 months of the year) Ordinary High Flow (= 1-year discharge) 40 cfs 6” 3 ft/sec (Highest ~1-3 months of the year) Annual High Flow (= 2-year discharge) 306 cfs 17” 4 ft/sec

TECHNICAL MEMORANDUM JANUARY 11, 2018 NORTH COUNTY LINE ROAD FISH PASSAGE PAGE 3 OF 4

4.3 Fish Swim Data Fish in the project area are mostly small species including creek chub, fathead minnows, darters, longnose dace, and sand shiner (per Colorado Parks and Wildlife Data included in the 2014 “Little Thompson Watershed Restoration Master Plan”). These species are generally one to five inches long. Based on a literature review completed for a five-inch long common shiner, the minimum water depth is four to five inches and the maximum prolonged swim speed is estimated to be 2.4 feet per second (ft/sec). The burst swim speed is estimated to be 4.5 ft/sec with a maximum duration of five seconds. This would allow the fish to swim 22 feet, which is not sufficient to swim through the 60-foot long culverts. Limited data for several smaller, approximately one-inch long, species related to those in the project area was found on the Oregon State University Swim Speed Table (http://www.fsl.orst.edu/geowater/FX3/help/SwimData/swimtable.htm). The prolonged swim speed for these species was between 1 ft/sec and 1.5 ft/sec.

Fish passage through the project area may be limited during the lowest and highest flows, although not significantly more than in other portions of the river. Shallow water will likely limit the passage of most fish during the driest parts of the year. Based on the above data, flow velocity would limit passage of small fish most of the year and larger fish during high flows. However, areas of slower water near the sides and bottoms of the culvert would allow fish passage for more of the year than the Table 1 data averages suggest.

5.0 Design Modifications to Improve Fish Passage

5.1 Boulders Based on the hydrologic and fish swim data, shallow water and high flow velocity could limit fish passage along the river during some of the year. In order to improve conditions in the project area, a cluster of three large (36-inch) boulders will be installed upstream of the bridge and near the east bank. The boulders will provide several benefits to fish. The primary benefit is to improve fish passage during high flows by reducing flow velocity within at least one of the culverts. Second, reduced flow velocity will cause sediment to drop out of the water upstream of the boulders. This could increase the relative depth of a low flow channel and improve fish passage in drier months. Third, boulder clusters can also generate scour that causes small pockets of deeper water to develop. The boulders and associated scour holes would provide hiding and resting areas for fish.

5.2 Concrete Apron Modification The preliminary design plans included a concrete apron on the upstream/south side of the crossing. The concrete sloped down from the road at a 3:1 ratio, extended to the riverbed, and then ended with a vertical, two-foot high, below grade, toe wall. If the channel were to erode at the toe wall, then the wall could be exposed and create a vertical barrier that would block fish passage during low flows. In order to

TECHNICAL MEMORANDUM JANUARY 11, 2018 NORTH COUNTY LINE ROAD FISH PASSAGE PAGE 4 OF 4

reduce the potential for the toe wall to block fish passage, the concrete apron on the south/upstream side of the crossing was extended so that it would end two feet below the channel bottom (Figure 1). Thus, the top of the vertical toe wall would be two feet below the channel.

Figure 1. Concrete Apron and Toe Wall Profile Detail from 100% Plans.

5.3 Re-vegetation Riparian vegetation around the crossing has been removed by flooding in 2013 and 2015. The project will help restore the area to pre-2013 flood conditions by re-seeding with native species, adding willow cuttings, and planting cottonwood trees. Increasing cover and shade along the channel will improve fish habitat and increase fish activity in the project area.

6.0 Conclusions Fish passage along the river, including the project area, may be limited by shallow water and high flows. Although the existing culverts will remain in place, several design elements will improve fish passage. Most importantly, a new concrete apron will be extended to so that the terminal toe wall will be buried two feet below the channel (Figure 1). This will reduce the chances of the toe wall creating a barrier to fish passage. Additionally, a cluster of boulders will be added reduce flow velocities through one of the culverts. The boulders and project re-vegetation will also improve fish habitat in the project area.

Geotechnical Engineering Report North 83rd Street and Little Thompson River Bridge Replacement Boulder County, Colorado Revised August 27, 2014 Terracon Project No. 22135032

Prepared for: J-U-B Engineers, Inc. 3538 JFK Parkway, Suite #1 Fort Collins, Colorado 80525

Prepared by: Terracon Consultants, Inc. 1242 Bramwood Place Longmont, Colorado 80501 TABLE OF CONTENTS

Page Executive Summary ...... i 1.0 INTRODUCTION ...... 1 2.0 PROJECT INFORMATION ...... 1 2.1 Project Description ...... 1 2.2 Site Location and Description ...... 2 3.0 SUBSURFACE CONDITIONS ...... 3 3.1 Typical Profile ...... 3 3.2 Laboratory Testing ...... 5 3.3 Groundwater ...... 6 4.0 RECOMMENDATIONS FOR DESIGN AND CONSTRUCTION ...... 7 4.1 Geotechnical Considerations ...... 7 4.1.1 Weathered Bedrock ...... 7 4.1.2 Drilling Difficulties ...... 7 4.1.3 Scour ...... 7 4.1.4 Low Strength Soils ...... 8 4.1.5 Foundation Type Recommendations ...... 8 4.2 Earthwork ...... 9 4.2.1 Site Preparation ...... 9 4.2.2 Fill/Backfill Material Types and Compaction ...... 9 4.2.3 Slopes ...... 10 4.2.4 Excavation and Dewatering ...... 11 4.3 Bridge Foundations ...... 12 4.3.1 Drilled Caisson/Pre-Drilled Pile Foundation Design Recommendations .. 12 4.3.2 Down Drag/Negative Skin Friction ...... 13 4.3.3 Drilled Caisson/Pre-Drilled Pile Construction Considerations ...... 14 4.4 Lateral Loading of Caissons/Pre-Drilled Piles ...... 14 4.5 Extension Wall Foundations...... 15 4.5.1 Extension Wall Foundation Design Recommendations...... 16 4.5.2 Extension Wall Foundation Construction Considerations ...... 16 4.6 Seismic Considerations ...... 17 4.7 Abutments and Wing Walls ...... 17 4.7.1 Lateral Earth Pressures ...... 18 4.7.2 Wall Drainage ...... 19 4.8 Pavements ...... 20 4.8.1 Existing Pavement Conditions ...... 20 4.8.2 Design Considerations ...... 21 4.8.3 Minimum Pavement Thickness ...... 22 4.8.4 Overlay Construction and Preparation ...... 23 4.8.5 Subgrade Preparation ...... 24 4.8.6 Pavement Drainage ...... 25 4.8.7 Pavement Performance and Maintenance ...... 25 4.9 Additional Design and Construction Considerations ...... 26 4.9.1 Soluble Sulfate Test Results (Concrete) ...... 26 5.0 GENERAL COMMENTS ...... 26

TABLE OF CONTENTS - continued

APPENDIX A – FIELD EXPLORATION Exhibit A-1 Field Exploration Description Exhibit A-2 Boring Location Plan Exhibits A-3 to A-10 Boring Logs

APPENDIX B – LABORATORY TESTING Exhibit B-1 Laboratory Testing Exhibits B-2 to B-5 Swell-Consolidation Test Results Exhibits B-6 to B-10 Grain Size Distribution/Soil Classification Results

APPENDIX C – SUPPORTING DOCUMENTS Exhibit C-1 General Notes Exhibit C-2 Unified Soil Classification Exhibit C-3 Rock Classification

August 27, 2014

J-U-B Engineers, Inc. 3538 JFK Parkway, Suite #1 Fort Collins, Colorado 80525

Attn: Mr. Jeff Temple, P.E. P: [970] 377 3602 E: [email protected]

RE: Geotechnical Engineering Report North 83rd Street and Little Thompson River Bridge Replacement Boulder County, Colorado Terracon Project Number: 22135032

Dear Mr. Temple:

Terracon Consultants, Inc. (Terracon) has completed the geotechnical engineering services for the project referenced above. This study was performed in general accordance with our proposal number P22130090 dated October 11, 2013. This revised report is being issued in response to comments on our original report dated December 11, 2013 and additional information provided by J-U-B Engineers, Inc. regarding bridge design and construction. This report presents the findings of the subsurface exploration and provides geotechnical recommendations concerning design and construction of bridge foundations (LRFD format), earthwork and pavement construction for the proposed project.

We appreciate the opportunity to be of service to you on this project. If you have any questions concerning this report, or if we may be of further service, please contact us.

Sincerely, Terracon Consultants, Inc.

27741 8/27/2014

Eric S. Willis, P.E. Eric D. Bernhardt, P.E. Senior Project Manager/Engineer Geotechnical Department Manager

Copies to: Addressee (via email)

Terracon Consultants, Inc. 1242 Bramwood Place, Ste. 2 Longmont, Colorado 80501 P [303] 776 3921 F [303] 776 4041 terracon.com Geotechnical Engineering Report N. 83rd St. & Little Thompson River Bridge ■ Boulder County, Colorado August 27, 2014 ■ Terracon Project No. 22135032

EXECUTIVE SUMMARY

A geotechnical engineering exploration has been performed for the proposed bridge replacement to be constructed at North 83rd Street and the Little Thompson River in Boulder County, Colorado. As requested, eight (8) borings, designated TB-1 through TB-7 and TB-4A, were performed to depths of about 10 to 40 feet below the existing ground surface.

Based on the information obtained from our subsurface exploration and laboratory testing program, the site is suitable for the proposed construction from a geotechnical point of view. The following geotechnical considerations were identified:

 Considering the size and type of construction planned, subsurface conditions encountered in our test borings and estimated scour depth, we believe that deep foundations consisting of caissons drilled into bedrock or pre-drilled piles encased in concrete and socketed into bedrock are appropriate for support of the bridge structure.

 Shallow water should be expected adjacent to the Little Thompson River and other water features on or adjacent to the site. Where groundwater is penetrated in excavations, some method of temporary dewatering will be needed for proper construction. Where permeable soils (such as sands/gravels) are encountered or if excavations penetrate water for a significant depth, the contractor should be prepared to use more extensive dewatering methods. Low strength soils and caving sands and gravels should be expected on the site and excavations into these materials will need to be laid back safely at flatter than normal slope inclinations, particularly if they are not adequately dewatered.

 On-site native soils typically appear suitable for use as general engineered fill on the site provided they are placed and compacted as described in this report. Abutment and wing wall backfill should consist of granular materials meeting the specifications for CDOT Class I structure backfill. Import materials should be evaluated and approved by the geotechnical engineer prior to delivery to the site.

 Close monitoring of the construction operations discussed herein will be important in achieving the intended foundation and pavement performance. We therefore recommend that Terracon be retained to monitor this portion of the work.

This summary should be used in conjunction with the entire report for design purposes. It should be recognized that details were not included or fully developed in this section, and the report must be read in its entirety for a comprehensive understanding of the items contained herein. The section titled GENERAL COMMENTS should be read for an understanding of the report limitations.

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GEOTECHNICAL ENGINEERING REPORT NORTH 83RD STREET AND LITTLE THOMPSON RIVER BRIDGE REPLACMENT BOULDER COUNTY, COLORADO Terracon Project No. 22135032 Revised August 27, 2014

1.0 INTRODUCTION

A geotechnical engineering report has been completed for the proposed bridge replacement to be constructed at North 83rd Street and the Little Thompson River in Boulder County, Colorado. As requested, eight (8) borings, designated TB-1 through TB-7 and TB-4A, were performed to depths of about 10 to 40 feet below the existing ground surface. Boring Logs along with a Boring Location Plan are included in Appendix A.

The purpose of these services is to provide information and geotechnical engineering recommendations relative to:

 subsurface soil and bedrock conditions  foundation design and construction  groundwater conditions  lateral earth pressures  earthwork  pavements  excavation and dewatering

The recommendations contained in this report are based on the results of field and laboratory testing, engineering analyses, experience with similar soil conditions and structures, and our understanding of the proposed project.

2.0 PROJECT INFORMATION

2.1 Project Description Item Description Site layout See Appendix A, Exhibit A-2, Boring Location Plan The project will include design and construction of a replacement bridge structure over the Little Thompson River. We understand the bridge will be 37 feet wide and will likely Bridge description be a four-span structure. Total length of the new bridge is reported to be on the order of about 250 feet. We assume the bridge deck will consist of reinforced concrete supported by concrete abutments and column supports at piers.

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Geotechnical Engineering Report N. 83rd St. & Little Thompson River Bridge ■ Boulder County, Colorado August 27, 2014 ■ Terracon Project No. 22135032

Item Description Based on a four-span structure with 24-inch deep box girders, we understand J-U-B expects the following loads: Anticipated loads Service Limit State: Abutments = 780 kips, Piers = 1,150 kips Strength 1 State: Abutments = 1,100 kips, Piers = 1,590 kips Lateral Loads: Abutments = 180 kips, Piers = 260 kips Information provided indicates the abutment/wing walls will Abutments/Wing Walls likely be about 10 feet tall. Wing walls are assumed to consist of cast-in-place (CIP) concrete construction. The existing road at the bridge approaches will be raised from its current elevation. Preliminary information provided Roadway embankment fill indicates about 6 feet of fill will be required at the location of the bridge abutments to achieve construction grades. Depending upon final grading, there may be a need to extend and create longer wing walls. We understand these extension walls will not be integral to the bridge structure and Miscellaneous retaining walls consideration may be given to supporting them on spread footings. These walls are reported to range from about 4 to 10 feet tall and will consist of cast-in-place (CIP) concrete construction. New pavement construction for the bridge approaches and beyond will also be completed for this project. Pavement Pavement construction construction will extend about 400 feet and 750 feet to the north and south of the bridge, respectively. Cut and fill slopes Assumed to be no steeper than 3H:1V (Horizontal to Vertical)

If project information varies from what is described above or if location of construction changes, we should be contacted as soon as possible to confirm and/or modify our recommendations accordingly.

2.2 Site Location and Description

Item Description The project site is located where North 83rd Street crosses Location the Little Thompson River in northern Boulder County, Colorado.

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Geotechnical Engineering Report N. 83rd St. & Little Thompson River Bridge ■ Boulder County, Colorado August 27, 2014 ■ Terracon Project No. 22135032

Item Description In general, the project site is surrounded by undeveloped and/or agricultural land. Although, scattered single-family homes are present in the vicinity of the project area. North 83rd Street is a two-lane asphalt surfaced street and crosses the Little Thompson River in the central part of the project area. The September 2013 flood event heavily damaged the Existing site features bridge and roadway. In particular, the east side of North 83rd Street was washed-out and the damage extended roughly 300 to 350 feet north of the river channel. At the time of our field explorations, a temporary river crossing structure was in place and consisted of eight (8) CMP culverts aligned in series. The pavement damage was also repaired and patched with a new asphalt section. The ground surface in the project area is relatively level with a gentle slope down towards the Little Thompson River. A difference in elevation of roughly 5 feet was estimated across Existing topography the location of our test borings. In addition, visual observation indicates the river channel bottom is about 6 feet below the adjacent pavement surface. The most prominent water feature in the vicinity of the project site is the Little Thompson River. Other water features Water features located within an approximate ½-mile radius of the site include the New Ish irrigation ditch, Highland Reservoir No. 2 and Blue Mountain Reservoir.

3.0 SUBSURFACE CONDITIONS

3.1 Typical Profile

Based on the results of the borings, subsurface conditions on the project site can be generalized as follows:

Bridge Test Borings Approximate Consistency or Depth to General Engineering Material Encountered Relative Density/ Bottom of Properties Hardness Stratum About 1½ to 4½ Existing Fill; Silty sand with feet in Borings 2, Loose Not determined gravel 4 and 4A

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Geotechnical Engineering Report N. 83rd St. & Little Thompson River Bridge ■ Boulder County, Colorado August 27, 2014 ■ Terracon Project No. 22135032

Bridge Test Borings Approximate Consistency or Depth to General Engineering Material Encountered Relative Density/ Bottom of Properties Hardness Stratum Low plasticity, essentially non-expansive, low to About 7 to 8½ Silty, clayey sand and/or Sands: Very loose moderate compressibility feet sandy silty clay Clays: Soft to very soft (settlement potential), low bearing capacity About 12 feet in Non-plastic, non-expansive, Sand with silt Loose Boring 1 only low load bearing capacity Sand and gravel with Non-plastic, non-expansive, About 14 to 19 varying amounts of silt, Medium dense to dense moderate load bearing feet contains some cobbles capacity Moderate plasticity, judged Extended to Medium hard to very to have low to moderate bottom of Claystone/siltstone bedrock hard swell potential, high load borings bearing capacity

Pavement Test Borings Approximate Consistency or Depth to General Engineering Material Encountered Relative Density/ Bottom of Properties Hardness Stratum

About 7 inches Asphalt concrete pavement N/A N/A

Aggregate base and/or About 12 to 24 Judged to offer good granular fill consisting of silty N/A inches pavement support sand with gravel Existing Fill; Silty and About 3 feet in Loose to medium dense Judged to offer fair to good clayey sand with varying Borings 5 and 6 pavement support amounts of gravel Low plasticity, non- About 7 to 9 Sands: Very loose Silty, clayey sand and/or expansive to slight swell feet in all Clays: Very soft to sandy silty clay potential, judged to offer fair borings medium stiff to poor pavement support

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Geotechnical Engineering Report N. 83rd St. & Little Thompson River Bridge ■ Boulder County, Colorado August 27, 2014 ■ Terracon Project No. 22135032

Pavement Test Borings Approximate Consistency or Depth to General Engineering Material Encountered Relative Density/ Bottom of Properties Hardness Stratum Extended to Sand with silt, trace fine bottom of Loose Non-plastic, non-expansive gravel Borings 5 and 7 Extended to bottom of Sand and gravel with silt Loose to medium dense Non-plastic, non-expansive Boring 6

Subsurface conditions encountered at each boring location are indicated on the individual boring logs. Stratification boundaries on the boring logs represent the approximate location of changes in soil types; in-situ, the transition between materials may be gradual. Details for each of the borings can be found on the boring logs in Appendix A.

3.2 Laboratory Testing

The laboratory testing program was designed to provide index and/or engineering properties for those soils/bedrock which influence foundation and pavement design and performance. The soil/bedrock samples tested for this study have the following physical and/or engineering properties:

Sample Liquid Plasticity Silt or Clay Expansion/Consolidation Boring Depth Limit Index Content (%/Surcharge Load psf) No. (ft.) (%) (%) (%) TB-1 4 39 23 5 -0.1/500 TB-1 9 10 NP NV TB-2 14 to 20 87 32 14 TB-3 9 8 NP NV TB-4 4 52 25 7 +0.0/500 TB-4A 9 37 23 4 TB-4 24 to 30 83 34 17 TB-5 4 39 22 4 TB-6 4 +0.1/200 TB-7 2 50 25 7 +0.3/200 NV = No Value; NP = Non-Plastic

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Geotechnical Engineering Report N. 83rd St. & Little Thompson River Bridge ■ Boulder County, Colorado August 27, 2014 ■ Terracon Project No. 22135032

3.3 Groundwater

The boreholes were observed while drilling and after completion for the presence and level of groundwater. The borings were backfilled shortly after drilling and therefore subsequent groundwater levels were not obtained. The water levels observed in the boreholes are noted on the attached boring logs, and are summarized below:

Depth to groundwater after completion Boring Number of drilling, ft. TB-1 7 TB-2 5 TB-3 6 TB-4 6 TB-4A 9 TB-5 9½ TB-6 7 TB-7 None encountered

These observations represent short-term groundwater conditions at the time of the field exploration, and may not be indicative of other times, or at other locations.

Groundwater levels can and should be expected to fluctuate with varying seasonal and weather conditions, irrigation demands on or adjacent to the site and with fluctuations in nearby water features. In particular, groundwater levels in the project area will be influenced, to a large degree, by the level of water in the Little Thompson River. Therefore, groundwater levels during construction or at other times in the future may be higher or lower than the levels indicated on the boring logs.

Fluctuations in groundwater levels can best be determined by implementation of a groundwater monitoring plan. Such a plan would include installation of groundwater monitoring wells, and periodic measurement of groundwater levels over a sufficient period of time. The possibility of groundwater level fluctuations should be considered and accounted for when developing the design and construction plans for the project.

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Geotechnical Engineering Report N. 83rd St. & Little Thompson River Bridge ■ Boulder County, Colorado August 27, 2014 ■ Terracon Project No. 22135032

4.0 RECOMMENDATIONS FOR DESIGN AND CONSTRUCTION

4.1 Geotechnical Considerations

Based on subsurface conditions encountered in our test borings, the site appears suitable for the proposed construction from a geotechnical point of view provided certain precautions and design and construction recommendations presented in this report are followed. We have identified a number of geotechnical conditions that could impact design and construction of the bridge foundations and other site improvements. These include very hard bedrock containing intermittent cemented lenses, a layer of weathered bedrock encountered at the contact between the overburden soils and the competent bedrock, estimated scour depths and low strength soils encountered in the upper part of the soil profile. These conditions are discussed in greater detail in the following sections.

4.1.1 Weathered Bedrock A layer of weathered bedrock is anticipated at the contact between the overburden soils and the bedrock on this site. Based on our boring data and experience in the area, it appears that a zone of weathered bedrock up to approximately 3 feet thick is present in the upper part of the bedrock formation at some locations. Consequently, we recommend these materials be ignored for side resistance when designing drilled caissons or pre-drilled piles encased in concrete. However, actual depth to competent bedrock should be determined by a representative of Terracon during caisson drilling operations.

4.1.2 Drilling Difficulties Field penetration tests and observation during the field exploration indicates that the competent bedrock is very hard and contains intermittent cemented lenses. Drilling to design depth should be possible on most of the site with heavy-duty caisson drill rigs. However, lenses and/or layers of very hard and cemented bedrock may be encountered at some locations and may require the use of a “rock bit” and/or core barrel to penetrate these materials. Water was encountered above the bedrock surface and caving soils are present on this site. In addition, our experience in the area suggests the bedrock formation can contain water-bearing seams. Accordingly, caissons or pre-drilled piles will require temporary casing and the use of a concrete pump truck with a tremie extension in order to control water infiltration and properly construct deep foundations.

4.1.3 Scour Preliminary scour information was provided by Anderson Consulting Engineers, Inc. and is summarized in the following table.

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Geotechnical Engineering Report N. 83rd St. & Little Thompson River Bridge ■ Boulder County, Colorado August 27, 2014 ■ Terracon Project No. 22135032

Estimated Total Scour Depth, Location / Scour Type feet North Abutment / 500-yr abutment scour 6 Pier 1 (northern Pier) / 500-yr pier and 100-yr contraction scour 1 14 Pier 2 (middle Pier) / 500-yr pier and 100-yr contraction scour 16 Pier 3 (southern Pier) / 500-yr pier and 100-yr contraction scour 21 South Abutment / 500-yr pier and 100-yr contraction scour 2 21 1100-yr flows produce the greatest amount of contraction scour, and to be conservative the total scour depth includes the greatest value for each type of scour. 2 It is assumed that bend scour would blow out the south approach road exposing the abutment piles, and that piles would cause pier scour

Considering the relatively shallow depth to the claystone/siltstone bedrock layer (approximately 10 to 14 feet below the existing river channel bottom), it is anticipated that scour depths maybe bedrock limited. Based on this information and the hardness of the bedrock, we believe that tip- bearing and/or driven piles are impractical for support of the bridge structure.

Bridge foundations should be protected from scour by armoring the stream channel. Armament should be placed to protect abutments, foundations and stream bank extending upstream and downstream from the bridge. A hydraulic engineer should be retained to design appropriate stream bank protection measures.

4.1.4 Low Strength Soils Very loose/soft and low strength clays and sands are present in the upper part of the soil profile on this site. Prior to placing fill, structures or pavements on very loose/soft, yielding subgrade, we recommend stabilization by either undercutting weak areas down to stable materials and replacement with select granular fill, or by placing a layer of crushed rock (nominal 3 to 6-inch size) and crowding it into the subgrade until a firm base is obtained. In any event, Terracon should be contacted to observe unstable soil conditions and provide guidance concerning the appropriate method and level of corrective work needed.

4.1.5 Foundation Type Recommendations Considering the size and type of construction planned, the subsurface conditions encountered in our test borings and the estimated scour depth, we believe that deep foundations consisting of caissons drilled into bedrock or pre-drilled piles encased in concrete and socketed into bedrock are appropriate for support of the bridge structure. Wing walls integral to the bridge structure should use the same type of foundation as the bridge.

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Geotechnical Engineering Report N. 83rd St. & Little Thompson River Bridge ■ Boulder County, Colorado August 27, 2014 ■ Terracon Project No. 22135032

Recommendations for the design and construction of bridge foundations, abutments/wing walls, pavements and other earth-connected phases of the project are presented in the following sections.

4.2 Earthwork

4.2.1 Site Preparation The following presents recommendations for site preparation, excavation, subgrade preparation and placement of engineered fills on the project. Earthwork on the project should be observed and evaluated by Terracon. The evaluation of earthwork should include observation and testing of engineered fill, subgrade preparation, foundation bearing soils, and other geotechnical conditions exposed during the construction of the project. Excavation, embankment construction and structure backfill should be completed in general accordance with the 2011 CDOT Standard Specifications for Road and Bridge Construction.

Before placing fill, the ground surface should be cleared of existing vegetation, topsoil and any loose, soft, or otherwise unsuitable material from the proposed construction area. Existing asphalt pavement should be removed at this time as well. Exposed surfaces should be free of mounds and depressions that could prevent uniform compaction. Following completion of stripping and grubbing, the exposed ground should be scarified, moisture conditioned as needed and re-compacted in accordance with the CDOT standards specifications.

Very loose/soft and low strength clays and sands are present in the upper part of the soil profile on this site. Prior to placing fill, structures or pavements on very loose/soft, yielding subgrade, we recommend stabilization by either undercutting weak areas down to stable materials and replacement with select granular fill, or by placing a layer of crushed rock (nominal 3 to 6-inch size) and crowding it into the subgrade until a firm base is obtained. In any event, Terracon should be contacted to observe unstable soil conditions and provide guidance concerning the appropriate method and level of corrective work needed.

Where new fill is placed on existing slopes steeper than 4H:1V (Horizontal:Vertical), the embankment should be continuously benched in general accordance with the 2011 CDOT Standard Specifications for Road and Bridge Construction (section 203.06). In general, benches should have a minimum vertical face height of about 2 feet and a maximum vertical face height of 5 feet and should be cut wide enough to accommodate compaction equipment. Benches should be sloped at about 2 percent towards the slope face.

4.2.2 Fill/Backfill Material Types and Compaction On-site soils free of vegetation, organic matter and other unsuitable materials or low volume change import materials approved by Terracon may be used as general fill/backfill material on the site.

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Geotechnical Engineering Report N. 83rd St. & Little Thompson River Bridge ■ Boulder County, Colorado August 27, 2014 ■ Terracon Project No. 22135032

In general, imported materials meeting the properties presented below are acceptable for use on the site. Imported soils should be evaluated and approved by the geotechnical engineer prior to delivery to the site.

Gradation Percent Finer by Weight (ASTM C136) 2-inch 100 No. 4 Sieve 30 to 100 No. 50 Sieve 10 to 60 No. 200 Sieve 5 to 20  Liquid Limit (LL) 30 (max)  Plasticity Index (PI) 6 (max)

Embankment fill should be placed and compacted in general accordance with CDOT Standard Specifications for Road and Bridge Construction, Subsections 203.06 and 203.07. Structure backfill should be placed and compacted in general accordance with the CDOT standard specifications, Subsection 206.03.

Engineered fill and backfill should be placed and compacted in horizontal lifts, using equipment and procedures that will produce recommended moisture contents and densities throughout the lift. A construction disc or other suitable processing equipment may be needed to aid in achieving uniform moisture content throughout the fill. The contractor should expect some moisture adjustment of the site soils or import materials will be needed prior to or during compaction operations.

4.2.3 Slopes For new slopes in compacted fill or cut areas where saturation of the slopes will not occur, we suggest slopes of 3:1 (Horizontal:Vertical), or less to reduce erosion and maintenance problems. Some local raveling and/or surface sloughing should be anticipated on slopes constructed at this angle until vegetation is re-established. If saturated or steeper slopes and/or slopes over about 10 feet in height are anticipated, or if structures or other surcharge loads will be located within a distance of the slope height from the crest of the slope, the slopes should be evaluated for stability on an individual basis.

The face of all slopes should be compacted to the minimum specification for fill embankments. Alternately, fill slopes can be over-built and trimmed to compacted soil. Slopes should be revegetated as soon as possible to reduce the potential for erosion problems. Seeded slopes should be protected with erosion mats until the vegetation is established. Surface drainage

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Geotechnical Engineering Report N. 83rd St. & Little Thompson River Bridge ■ Boulder County, Colorado August 27, 2014 ■ Terracon Project No. 22135032

should be designed to direct water away from slope faces and to prevent ponding adjacent to the crest or toe of the slope.

4.2.4 Excavation and Dewatering We believe the soils encountered on the site can be excavated with conventional heavy-duty excavation equipment such as large trackhoes. If bedrock is penetrated in excavations, difficult excavation of these materials should be expected. Excavations penetrating the bedrock (if any) may require the use of large rippers, pneumatic hammers or other specialized heavy-duty equipment to advance the excavation. Consideration should be given to obtaining a unit price for difficult excavation in the contract documents for the project. Low strength soils and caving sands and gravels should be expected on the site and excavations into these materials will need to be laid back safely at flatter than normal slope inclinations, particularly if they are not adequately dewatered.

Shallow water should be expected adjacent to the Little Thompson River and other water features on or adjacent to the site. The groundwater level is significantly influenced by the level of water in the Little Thompson River. In order to achieve adequate dewatering, the flow can be diverted into culverts to bypass the construction area. Temporary cofferdams may be needed upstream to direct the flow into the culverts.

Where groundwater is penetrated in excavations, some method of temporary dewatering will be needed for proper construction. For excavations that penetrate groundwater for only a shallow depth, it may be possible to dewater by sloping the excavation to isolated sumps and pumps. Where more permeable soils (such as sands/gravels) are encountered or if excavations penetrate water for a significant depth, the contractor should be prepared to use more extensive dewatering methods.

Dewatering should be started prior to beginning construction and should continue through excavation, foundation construction and backfilling operations to ensure proper construction. Temporary construction dewatering should ideally be designed to maintain groundwater at least 2 feet below the level of the excavation. The sumps and pumps should be situated several feet below the bottom of the excavation to draw water down through the soil rather than up through the bottom of the excavation in order to reduce the potential for destabilization of the base of the excavation.

The individual contractor(s) is responsible for designing and constructing stable, temporary excavations in order to maintain stability of excavation sides and bottom as well as any adjacent structures and foundations. Excavations should be sloped or shored in the interest of safety following local and federal regulations, including current OSHA excavation and trench safety standards. If any excavation extends to a depth greater than 20 feet, according to OSHA regulations, the side slopes must be designed by a professional engineer.

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Geotechnical Engineering Report N. 83rd St. & Little Thompson River Bridge ■ Boulder County, Colorado August 27, 2014 ■ Terracon Project No. 22135032

The soils to be penetrated by the proposed excavations may vary significantly across the site. The preliminary soil classifications are based solely on the materials encountered in widely spaced exploratory test borings. The contractor should verify that similar conditions exist throughout the proposed area of excavation. If different subsurface conditions are encountered at the time of construction, the actual conditions should be evaluated to determine any excavation modifications necessary to maintain safe conditions.

4.3 Bridge Foundations

Considering the size and type of construction planned, the subsurface conditions encountered in our test borings and the estimated scour depth, we believe that deep foundations consisting of caissons drilled into bedrock or pre-drilled piles encased in concrete and socketed into bedrock are appropriate for support of the bridge structure. Wing walls integral to the bridge structure should use the same type of foundation as the bridge. Design criteria and construction recommendations for deep foundations are provided in the following sections.

4.3.1 Drilled Caisson/Pre-Drilled Pile Foundation Design Recommendations Description Design Parameter Bearing stratum 1 Claystone/siltstone bedrock Location Elevation (feet) North Abutment 5,088 Pier 1 (northern Pier) 5,089 Estimated Competent Bedrock Elevation Pier 2 (middle Pier) 5,089 Pier 3 (southern Pier) 5,088 South Abutment 5,086 Minimum penetration into competent bedrock 6 feet Minimum shaft length 2 15 feet Nominal end-bearing 3 150 ksf Axial compression pressure in bedrock loads Nominal skin friction for 10 ksf bedrock 3 Nominal skin friction for uplift resistance 4 10 ksf 1. Based on our boring data and experience in the area, it appears that a zone of weathered bedrock up to approximately 3 feet thick is present in the upper part of the bedrock formation at some locations. These materials should be ignored for side resistance when designing deep foundations. However, actual depth to competent bedrock should be determined by a representative of Terracon during drilling operations. 2. Longer shaft lengths may be necessary to achieve proper bedrock penetration or required by

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Geotechnical Engineering Report N. 83rd St. & Little Thompson River Bridge ■ Boulder County, Colorado August 27, 2014 ■ Terracon Project No. 22135032

structural loading or other conditions. 3. The end-bearing pressure and skin friction values are applicable for the portion of the foundation in competent bedrock. Skin friction within soils overlying the bedrock should be neglected. 4. Caissons/pre-drilled piles may be designed to resist uplift forces. Uplift resistance can be increased by additional penetration into competent bedrock. 5. Movement of properly designed and constructed caissons/pre-drilled piles should be on the order of about ½ inch at the service limit loads.

Resistance factors for design of drilled caissons/pre-drilled piles are summarized below.

Item Value Tip Resistance Factor – Strength Limit State 0.5 Side Resistance Factor – Strength Limit State 0.5 Uplift Resistance for Single Foundation Element – Strength Limit State 0.4 1.0 except 0.8 should Tip and Side Resistance – Extreme Limit State be used for uplift

The nominal bearing resistance of a group of drilled caissons should be the lesser of (1) the sum of the individual nominal resistances for each drilled caisson in the group and (2) the nominal resistance of an equivalent pier consisting of the drilled caissons and the block of soil within the area bounded by the drilled caissons. If the drilled caisson cap is not in firm contact with the ground, the nominal resistance of each drilled caisson should be reduced as indicated in section 10.7.3.9 of AASHTO.

Drilled caissons/pre-drilled piles should have a center-to-center spacing of at least 3 diameters. Each interior bent should have a minimum of two (2) drilled caissons.

Caissons should be reinforced full depth for the applied axial, lateral and uplift stresses imposed. Reinforcement should be in accordance with AASHTO design requirements and should not be less than 1 percent times the gross cross-sectional area of the caisson. More reinforcement may be required because of structural considerations.

Caissons/pre-drilled piles should have a minimum diameter of 24 inches and a preferred maximum L/D ratio of 20 to 25, with 30 considered the typical limit. Larger diameters may be needed to accommodate actual foundation load and other structural design requirements.

4.3.2 Down Drag/Negative Skin Friction Negative skin friction is a downward shear drag acting on deep foundations due to downward movement of surrounding soil strata relative to the caissons. For such movement of the soils to occur, a segment of the foundation element must penetrate a compressible soil stratum that

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Geotechnical Engineering Report N. 83rd St. & Little Thompson River Bridge ■ Boulder County, Colorado August 27, 2014 ■ Terracon Project No. 22135032

consolidates. Downward drag may be caused by placement of fill on compressible soils, lowering of the groundwater table or other factors. Considering the planned depth of fill at the location of the abutments (about 6 feet), and since the soils on the site are essentially granular in nature, settlement is expected to be minor and should occur quickly. Consequently, we do not believe that down drag loads are significant and need to be considered in design of the bridge foundations.

4.3.3 Drilled Caisson/Pre-Drilled Pile Construction Considerations Caisson construction should be performed in general accordance with Section 503 of the 2011 CDOT Standard Specifications for Road and Bridge Construction. Drilling to design depth should be possible on most of the site with heavy-duty caisson drill rigs. However, lenses and/or layers of very hard and cemented bedrock may be encountered at some locations and may require the use of a “rock bit” and/or core barrel to penetrate these materials.

Water was encountered above the bedrock surface and caving soils are present on this site. In addition, our experience in the area suggests the bedrock formation can contain water-bearing seams. Accordingly, caissons will require temporary casing and the use of a concrete pump truck with a tremie extension in order to control water infiltration and properly construct foundations. Concrete should be on site and placed immediately after the holes are drilled, thoroughly cleaned and inspected. Casing should be withdrawn in a slow continuous manner maintaining a sufficient head of concrete in the casing to prevent infiltration of water or the creation of voids in caisson concrete.

Foundation concrete should have a relatively high fluidity when placed in cased holes or through a tremie. Free-fall concrete placement will not be acceptable. The use of a concrete pump truck with a tremie discharging concrete at the bottom of the hole is recommended.

The construction of drilled caissons/pre-drilled piles should be observed by a representative of Terracon on a full-time basis in order to identify the appropriate bearing strata, observe the construction methods being used and to confirm that subsurface conditions are consistent with those encountered in our test borings.

4.4 Lateral Loading of Caissons/Pre-Drilled Piles

Drilled caissons/pre-drilled piles should be designed to resist lateral loads applied to the structure by seismic, wind and other lateral forces. The following material values can be used to develop deflection versus moment curves for laterally loaded caissons using the LPILE computer program.

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Geotechnical Engineering Report N. 83rd St. & Little Thompson River Bridge ■ Boulder County, Colorado August 27, 2014 ■ Terracon Project No. 22135032

Modulus of Average Angle of Average Horizontal Strain at 50% Soil Model Unit Internal Undrained Material Type Subgrade of Maximum Type Weight,  Friction,  Shear Strength, Reaction, k Stress, 50 (pcf) (degrees) cu (psf) (pci) Engineered Fill - CDOT Class I Sand 125 34 -- 90 -- Structure Backfill (Reese) (above water) Sandy Silty Clays/Silty Clayey Soft Clay 115 0 250 30 0.02 Sands Native Sands/Gravels Sand 65 33 -- 60 -- (below water) (Reese) Claystone/Siltstone Stiff Clay Static - 2,000 130 0 9,000 0.003 Bedrock without water Cyclic - 800

Lateral resistance should be adjusted for group effects as indicated in Table 10.7.2.4-1 of AASHTO. All materials above estimated scour depth should be neglected in the lateral load analysis.

4.5 Extension Wall Foundations

Depending upon final grading, there may be a need to extend and create longer wing walls. We understand these extension walls will not be integral to the bridge structure and consideration may be given to supporting them on spread footings. These walls are reported to range from about 4 to 10 feet tall and will consist of cast-in-place (CIP) concrete construction. Foundation bearing depth is anticipated to be around elevation 5104 feet. If actual foundation bearing depth differs significantly, we should be contacted to confirm and/or modify our recommendations accordingly.

Spread footings could be subject to undermining by scour. The channel floor and sides under the bridge, and upstream and downstream of the bridge should be protected from scour or the footings should be placed below the anticipated scour depth. Undermining of scour protection must be prevented. A hydraulic engineer should be retained to design appropriate scour protection measures.

Based on our boring data, we expect low strength sands/clays or possibly existing fill materials will be encountered at or near anticipated foundation bearing depth. To provide more uniform and predictable support and to provide a relatively stable base for construction, we recommend footings be supported on at least 3 feet of select granular fill or washed rock. Over-excavation should also extend at least 2 feet beyond the footing edges.

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Geotechnical Engineering Report N. 83rd St. & Little Thompson River Bridge ■ Boulder County, Colorado August 27, 2014 ■ Terracon Project No. 22135032

4.5.1 Extension Wall Foundation Design Recommendations Description Spread Footing Design Parameter Minimum 3-foot zone of select granular fill or Bearing material washed rock Nominal/Ultimate Allowable Soil bearing pressure 1 6 ksf 2 ksf Minimum embedment below finished grade 2 36 inches Estimated post-construction movement About 1 inch Above water 350 psf/ft Ultimate passive pressure 3 Below water 165 psf/ft Ultimate Coefficient of sliding friction at base of 0.40 footing on sand/gravel 3 1. The bearing pressure assumes no slope in front of the wall toe, a minimum footing width of at least 3 feet and a minimum embedment depth of at least 3 feet. 2. For frost protection and confinement of the bearing materials in order to develop the recommended soil bearing pressure. 3. Backfill must be compacted to at least 95 percent of the maximum dry density as determined by AASHTO T-180 for the passive earth pressure values to be valid. Passive resistance in the upper 3 feet of the soil profile should be neglected. 4. Global stability of the wall system should be considered for walls supported on or adjacent to existing slopes or new embankment slopes. Global slope stability analysis is outside of our current scope of work; however, we would be pleased to provide a proposal and cost estimate for additional analysis upon your request.

A bearing resistance factor of 0.5 for extension walls may be applied when using the Load Resistance Factor Design (LRFD) method.

Reinforced concrete walls should be designed for earth pressures at least equal to those indicated in section 4.8.1 Lateral Earth Pressures.

4.5.2 Extension Wall Foundation Construction Considerations To help provide a relatively stable base for construction and foundation support, we recommend foundations be placed on at least 3 feet of select granular fill or washed rock. Over-excavation should also extend at least 2 feet beyond the footing edges. Select granular fill meeting the specifications for CDOT Class I structure backfill (or other approved materials) can be used below footings. Select granular fill should be moisture conditioned within 2 percent of optimum moisture content and compacted to at least 95 percent of the maximum dry density as determined by AASHTO T-180.

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Geotechnical Engineering Report N. 83rd St. & Little Thompson River Bridge ■ Boulder County, Colorado August 27, 2014 ■ Terracon Project No. 22135032

Washed rock could also be used below footings and should meet the specifications of ASTM C33, Size No. 57 or 67 or other approved materials. Washed rock should be placed in maximum 12- inch lifts and densified with a vibratory compactor. More extensive stabilization efforts (such as a greater thickness of select granular fill/washed rock and/or the use of geo-grid) may be needed if highly unstable soils and/or groundwater are encountered in the excavation.

Footings and walls should be reinforced as necessary to reduce the potential for distress caused by differential movements. Frequent control joints are recommended in concrete walls to control cracking.

The base of all foundation excavations should be free of water and loose soil prior to concrete placement. Concrete should be placed soon after excavating to reduce bearing soil disturbance. Should the soils at bearing level become excessively dry, disturbed or saturated, or frozen, the affected soil should be removed prior to placing concrete.

Footing excavations should be observed by a representative of Terracon well in advance of forming footings to confirm satisfactory bearing materials are present and that subsurface conditions are as anticipated from our test borings. If the soil conditions encountered differ significantly from those presented in this report, supplemental recommendations will be required.

4.6 Seismic Considerations

Based on Section 3.10 of AASHTO, the site classifies as Site Class D. Interpolations of mapped spectral accelerations (Site Class B) for zero period (PGA), short Period (Ss), and long period

(S1) are 0.06g, 0.13g, and 0.03g, respectively. These values have a 7 percent probability of exceedence in 75 years, or a return period of approximately 1,000 years. These values should be adjusted for Site Class D in accordance with section 3.10 of AASHTO.

4.7 Abutments and Wing Walls

We anticipate abutment/wing wall construction associated with the bridge structure. Information provided indicates abutment walls will be about 10 feet tall. In addition, extension walls independent of the bridge structure may be required for the project and will range from about 4 to 10 feet tall. Wall backfill should consist of granular materials meeting the specifications for CDOT Class I structure backfill. If different type of backfill, taller walls, or modular block-geogrid reinforced backfill walls are planned for this project, we should be contacted to review our data and the wall geometry to determine whether further field exploration and/or engineering analysis is necessary to provide appropriate design criteria.

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Geotechnical Engineering Report N. 83rd St. & Little Thompson River Bridge ■ Boulder County, Colorado August 27, 2014 ■ Terracon Project No. 22135032

4.7.1 Lateral Earth Pressures Walls with unbalanced backfill levels on opposite sides should be designed for earth pressures at least equal to those indicated in the following table. Earth pressures acting on the abutments/ wing walls will be influenced by structural design, conditions of wall restraint, methods of construction and/or compaction and the strength of the materials being restrained. Two wall restraint conditions are shown. Active earth pressure is commonly used for design of free-standing cantilever retaining walls and assumes wall movement. The "at-rest" condition assumes no wall movement.

The lateral earth pressures are ultimate/nominal values and do not provide for possible hydrostatic pressure on walls. Furthermore, they do not include the influence of surcharge, such as adjacent traffic and construction materials. No consideration was given to sloping backfill and its influence on the lateral earth pressures. Additional recommendations may be necessary if sloping backfills are to be included in the design.

EARTH PRESSURE COEFFICIENTS

Earth Pressure Coefficient for Equivalent Fluid Surcharge Earth Pressure,

Conditions Backfill Type Density (pcf) Pressure, p1 (psf) p2 (psf) Active (Ka) Granular - 0.30 40 (0.30)S (40)H At-Rest(Ko) Granular - 0.46 60 (0.46)S (60)H Passive (Kp) Granular – 3.0 400 -- --

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Geotechnical Engineering Report N. 83rd St. & Little Thompson River Bridge ■ Boulder County, Colorado August 27, 2014 ■ Terracon Project No. 22135032

Applicable conditions to the above include:

 For active earth pressure, wall must rotate about base, with top lateral movements of about 0.002 H to 0.004 H, where H is wall height  For passive earth pressure to develop, wall must move horizontally to mobilize resistance  Uniform surcharge, where S is surcharge pressure  In-situ soil backfill weight a maximum of 125 to 130 pcf  Horizontal backfill  Loading from heavy compaction equipment not included  No hydrostatic pressures acting on wall  No dynamic loading  Ignore passive pressure in frost zone

Backfill placed against abutments/wing walls should consist of granular materials meeting the specifications for CDOT Class I structure backfill. Claystone/siltstone bedrock materials or clay soils should not be used as backfill against abutments and wing walls. For the granular values to be valid, the granular backfill must extend out from the base of the wall at an angle of at least 45 and 60 degrees from vertical for the active and passive cases, respectively.

Fill against abutments/wing walls and head walls should be placed and compacted as presented in section 4.2 Earthwork. Compaction of each lift adjacent to walls should be accomplished with hand-operated tampers or other lightweight compactors. Heavy equipment should not operate within a distance closer than the exposed height of the wall to prevent lateral pressures more than those provided. Over-compaction may cause excessive lateral earth pressures which could result in wall movement.

The magnitude of backfill settlement associated with the abutments and wing walls will be directly related to the type of fill, the degree of compaction and the thickness of the backfill layer. Backfill consisting of select import granular material (such as CDOT Class 1 structure backfill) can be expected to settle about 1 to 1½ percent of its original height even when properly compacted. This can lead to a condition where a dip/depression forms on the backfill side of the abutment over time. Paving should be delayed as long as possible to allow for some backfill settlement. We recommend provisions be made for a maintenance program that will periodically fill any dips/depressions to provide a smooth transition to the bridge or abutment wall.

4.7.2 Wall Drainage To control the water level and reduce hydrostatic pressure behind earth-retaining walls, a drainage system could be installed behind the walls. If this is not possible, then combined hydrostatic and lateral earth pressures should be calculated for select granular backfill materials below water using an equivalent fluid weighing 85 and 95 pcf for active and at-rest conditions, respectively.

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Geotechnical Engineering Report N. 83rd St. & Little Thompson River Bridge ■ Boulder County, Colorado August 27, 2014 ■ Terracon Project No. 22135032

Free-draining gravel backfill should be used behind retaining walls to help relieve hydrostatic pressure and provide drainage. We recommend a free-draining gravel material with less than 5 percent fines (material passing the No. 200 sieve) be used for a zone within at least 1-foot against the back of the wall. Free-draining gravel should be graded to prevent the intrusion of fines or encapsulated in a suitable filter fabric. Where the top of the backfill zone is not covered with pavement or flatwork, we recommend the entire backfill zone be capped with at least 18 inches of compacted clay fill to reduce infiltration and conveyance of surface water through the wall backfill.

To facilitate drainage, weep holes and/or installation of a drain pipe at the base of the free- draining backfill zone should be provided. If a drain pipe is installed, it should consist of a minimum 4-inch diameter perforated PVC pipe encased in free-draining gravel. The drain pipe should slope at least ½ percent to a positive gravity outlet at either or both ends of the wall, or be connected to outfall more than 5 feet in front of the wall.

As an alternative, a manufactured wall drain such as Miradrain could be used as a substitute for the gravel backfill zone adjacent to the back of the wall. Manufactured drains should be installed following the manufacturer’s recommendations.

4.8 Pavements

We understand pavement reconstruction or rehabilitation for a portion of N. 83rd Street will be completed as part of this project. At the time of this report, it was not known whether total reconstruction or rehabilitation (asphalt overlay) will be used for pavement construction since final street grades have not been established. Therefore, we are providing recommendations for construction of a new pavement section as well as an asphalt overlay.

4.8.1 Existing Pavement Conditions As part of the field investigation, we measured the asphalt thickness at each pavement boring location. The existing asphalt concrete pavement thickness was measured at approximately 7 inches at the test boring locations. Aggregate base course appeared to be present below the existing asphalt concrete in all test borings and ranged from about 6 to 10 inches thick.

The September 2013 flood event heavily damaged portions of the roadway. In particular, the east side of North 83rd Street was washed-out and the damage extended roughly 300 to 350 feet north of the river channel. At the time of our field exploration, the pavement damage was repaired and patched with a new asphalt section. We measured the asphalt thickness at three (3) locations along the east edge of the new asphalt patch. Asphalt thickness ranged between approximately 4 to 5 inches at the locations checked. Aggregate base course extended to a depth of at least 8 inches below the asphalt concrete.

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Geotechnical Engineering Report N. 83rd St. & Little Thompson River Bridge ■ Boulder County, Colorado August 27, 2014 ■ Terracon Project No. 22135032

Furthermore, we conducted a limited visual distress survey of the asphalt concrete pavement. The distress survey was performed to provide a subjective evaluation of the pavement condition and distresses observed. Based on our visual observations, we judge the majority of the existing asphalt concrete pavement to be in fair to good condition. In general, we observed distresses in the form of low to moderate severity transverse cracking at regular intervals of about 50 to 100 feet.

4.8.2 Design Considerations Boulder County requires use of the Colorado Department of Transportation (CDOT) design method. North 83rd Street is a two-lane asphalt surfaced street. In general, the project area is surrounded by agricultural and/or undeveloped land. Although, scattered single-family homes are present in the vicinity of the project area.

Results of gradation and plasticity tests indicate the native subgrade materials classify as A-4 soils according to the AASHTO classification system. AASHTO group indices of these soils ranged from 0 to 1. These subgrade materials have "CL-ML" and "SC-SM" classifications in accordance with the Unified Soil Classification System (USCS) methods. Soil classification test results and our experience indicate the subgrade soils at the site offer fair to poor pavement support when properly compacted and drained.

The average daily traffic (ADT) value for the street was provided by the client. In addition, we used a growth factor of 2 percent along with 4 percent truck traffic (2% single unit trucks and 2% combination trucks) for the street. The Equivalent Daily Load Application (EDLA) value was determined using the projected ADT value of the mid-point of the design period and applying appropriate 18-kip equivalency and lane distribution factors provided in the CDOT Pavement Design Manual. A 20-year design life for new pavement construction and a 10-year design life for rehabilitation (asphalt overlay), as outlined in the CDOT Pavement Design Manual, was used to develop the total traffic for the design period.

Design parameters or other data used for determining pavement thickness for this project are summarized in the following table.

Design Parameter/Data Value ADT Value (provided by client) 1,900

Correlated Soil/Subgrade Resilient Modulus (MR) 5,000 psi Reliability 85%

Overall Standard Deviation (So) 0.44 Design Serviceability Loss (ΔPSI) 2.0

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Geotechnical Engineering Report N. 83rd St. & Little Thompson River Bridge ■ Boulder County, Colorado August 27, 2014 ■ Terracon Project No. 22135032

Design Parameter/Data Value 18-kip Equivalent Daily Load 10-year design period 37 Application (EDLA) 20-year design period 42 Required Structural Number 10-year design period 2.74

(SNR) 20-year design period 3.11

Estimated Effective Structural Number of Existing Pavement (SNEFF) 2.8 New Asphalt Concrete (AC) 0.44 Pavement Layer New Aggregate Base Course (ABC) 0.12 Strength Coefficient Existing Asphalt Concrete (AC) 0.35 Existing Aggregate Base Course (ABC) 0.09

Using the values presented in the table, environmental criteria and other factors, the required structural number (SNR) of the pavement section was determined on the basis of the 1993 AASHTO design equation.

4.8.3 Minimum Pavement Thickness Typical Pavement Section Thickness (inches) Asphalt Aggregate Concrete Option Alternative Base Total Thickness Surface 2 1 Course Course AC + ABC 5 8 13 Total Reconstruction AC 7 -- 7

Asphalt Overlay 3 AC 1½ -- 1½ 1. Material meeting CDOT Grading SX, S or SG specification is recommended for asphalt concrete (AC) for total reconstruction. CDOT Grading SX is recommended for the asphalt overlay option. Asphalt concrete should be placed in maximum 3-inch lifts (4-inch max for SG) and compacted to a minimum of 95% Hveem density (ASTM D1560, D1561) or to a density of 92 to 96 percent of the maximum theoretical density, determined in general accordance with ASTM D2041 (Colorado Procedure 51). Mix designs should be submitted prior to construction to verify their adequacy. 2. Aggregate base course (ABC) should consist of a blend of sand and gravel which meets strict specifications for quality and gradation and should have an R-value of at least 78. Use of materials meeting Colorado Department of Transportation (CDOT) Class 5 or 6 specifications is recommended for base course. ABC should be placed in lifts not exceeding 6 to 8 inches, moisture conditioned within 2 percent of optimum and compacted to at least 95 percent of the modified Proctor maximum dry density (ASTM D1557/AASHTO T180). 3. Visual observation of the pavement condition and subjective evaluation of the strength of the

pavement components suggests the effective structural number (SNEFF) of the existing pavement

section is equal to or greater than the required structural number (SNR) for the street. Therefore, the

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Geotechnical Engineering Report N. 83rd St. & Little Thompson River Bridge ■ Boulder County, Colorado August 27, 2014 ■ Terracon Project No. 22135032

pavement section appears to be structurally adequate to support the anticipated traffic volumes over the performance period. Consequently, it is our opinion that a structural asphalt overlay is not strictly warranted at this time provided adequate and timely pavement maintenance is performed. However, a non-structural (functional) overlay could be considered for aesthetic purposes.

It should be recognized the overlay section thickness recommended in this report is based, in part, on a visual and subjective evaluation of the condition and structural capacity of the existing pavement section. Falling Weight Deflectometer (FWD) testing could be used to substantiate and/or modify overlay design requirements. Terracon has the capability to provide FWD testing and evaluation services. We are available to discuss FWD testing in greater detail and could provide a cost estimate for providing these additional services upon your request.

The pavement sections presented are based, in part, on design parameters selected by Terracon based on experience with similar projects and soil conditions, information provided by the client and information contained in the CDOT Pavement Design Manual. Design parameters such as serviceability loss, reliability, EDLA values and other factors presented above may vary with specific project requirements. Variation of these parameters may change the thickness of the pavement sections presented. Terracon is prepared to discuss the details of these parameters and their effects on pavement design and reevaluate pavement thickness as appropriate.

4.8.4 Overlay Construction and Preparation As discussed previously, we conducted a limited visual distress survey of the asphalt concrete pavement. Based on our visual observations, we judge the majority of the asphalt concrete pavement to be in fair to good condition. At the time of our site reconaissance, we observed distresses primarily in the form of low to moderate severity transverse cracking at regular intervals of about 50 to 100 feet. However, other pavement distresses could develop over time.

The following types of distress should be identified and repaired prior to placement of an asphalt overlay section. If these distresses are not properly repaired, the service life of the overlay will be reduced.

 Linear Cracks: These distresses may include both longitudinal and transverse cracks as well as edge cracking. Areas of high severity linear cracks should be patched. Linear cracks that exceed about ¼ inch in width should be filled with a sand-asphalt mixture or other suitable crack filler material. Some method of reflective crack control is recommended for transverse cracks that experience significant opening and closing.

 Alligator (Fatigue) Cracking: Areas of high severity alligator cracking must be patched. Localized areas of medium severity alligator cracking should also be patched unless a paving fabric/geotextile or other means of reflective crack control is used. Patching

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Geotechnical Engineering Report N. 83rd St. & Little Thompson River Bridge ■ Boulder County, Colorado August 27, 2014 ■ Terracon Project No. 22135032

operations should include removal and replacement of any soft/weak subgrade materials below the pavement section.

 Rutting: Ruts should be removed by placement of a leveling course or by milling. If milling is performed, a structural asphalt replacement depth must be included to account for the removed asphalt material. This replacement depth is in addition to the overlay design depth required to satisfy traffic loadings. If rutting is severe, removal and replacement with an asphalt patch and appropriate subgrade stabilization will be required.

 Potholes: Potholes should be cleaned and all loose materials removed. The affected area should then be patched with asphalt concrete.

4.8.5 Subgrade Preparation After removal of existing asphalt and prior to placement of fill or pavement sections, the subgrade should be scarified to a minimum depth of 12 inches, moisture conditioned and compacted. Clay subgrade soils should be moisture conditioned within 1 percent below to 3 percent above optimum moisture content (unless modified by the project geotechnical engineer) and compacted to at least 95 percent of the standard Proctor maximum dry density (ASTM D698/AASHTO T99). Granular subgrade soils (sands/gravels) should be compacted within plus or minus 2 percent of optimum moisture to at least 95 percent of the standard Proctor maximum dry density (ASTM D698/AASHTO T99).

Fill placed below the pavement should consist of clean on-site soils or non-expansive to low swelling soil approved by the geotechnical engineer having an R-value of at least 20. The fill should be placed in thin, loose lifts and compacted. We recommend fill placed at the site be moisture conditioned as described above and compacted to at least 95 percent of the standard Proctor maximum dry density (ASTM D 698/AASHTO T99). Fill should not contain organic or frozen material and it should not be placed on a frozen subgrade.

Our experience indicates that subgrade materials below existing pavements will likely have relatively high moisture content and will tend to deflect and deform (pump) under construction traffic wheel loads. This condition is most likely due to moisture collecting in the subgrade through cracks or seams in the pavements and lack of natural evaporation which would allow for drying of the subgrade. After removal of pavements, the contractor should expect some unstable subgrade materials that will need to be stabilized prior to construction of new pavements. Consequently, Terracon recommends a contingency be provided in the construction budget to stabilize and correct weak/unstable subgrade.

Terracon anticipates the subgrade can be stabilized by scarifying the exposed soils to a depth of at least 12 inches, processing the scarified materials, allowing the soils to dry, and then

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Geotechnical Engineering Report N. 83rd St. & Little Thompson River Bridge ■ Boulder County, Colorado August 27, 2014 ■ Terracon Project No. 22135032

compacting the subgrade materials in-place. If scarifying and drying is performed, several days may be required before the subgrade is stable enough for recompaction and paving, depending on weather conditions and other factors. However, the contractor should be prepared to perform more aggressive stabilization methods. More aggressive stabilization techniques could involve undercutting weak areas and replacement with select granular fill and possibly geogrid mats, or by placing a layer of angular rock and crowding it into the subgrade until a firm base is obtained.

After the subgrade has been prepared and compacted as described above and shortly before base course and/or asphalt placement, we recommend the exposed pavement surface be proof- rolled to delineate soft/weak or disturbed areas at or near subgrade level. Heavy construction equipment such as a loaded water truck or tandem axle dump truck is recommended for proof- rolling. Areas showing excessive deflection and deformation should be over-excavated and replaced with approved fill if the affected materials cannot be moisture adjusted and compacted in place, or the subgrade should be stabilized by other methods described above.

Placement and compaction of subgrade soils, base course and other pavement materials should be observed and tested by Terracon to verify the specified moisture and/or compaction requirements have been achieved.

4.8.6 Pavement Drainage Pavements should be sloped to provide rapid drainage of surface water. Adequate slopes adjacent to the roadway should be re-established and maintained to promote surface water drainage away from the pavement system. Water allowed to pond on or adjacent to the pavements could saturate the subgrade and contribute to premature pavement deterioration. Collection and diversion of surface drainage away from paved areas is critical to satisfactory performance of pavements.

4.8.7 Pavement Performance and Maintenance Our experience indicates longitudinal cracking is common for asphalt pavements. The cracking normally occurs parallel to the interface between asphalt and concrete features such as curbs, gutters or drain pans and/or several feet in from pavement edges. The mechanism for this cracking is not fully understood, but seems to be most prevalent for expansive and/or cohesive subgrade soils. Distress of this type is likely to occur even if the subgrade has been properly prepared and the asphalt has been compacted properly.

The pavement sections provided in this report represent minimum recommended thicknesses and, as such, periodic maintenance should be anticipated. Therefore preventive maintenance should be planned and provided for through an on-going pavement management program. Preventive maintenance activities are intended to slow the rate of pavement deterioration, and to preserve the pavement investment.

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Geotechnical Engineering Report N. 83rd St. & Little Thompson River Bridge ■ Boulder County, Colorado August 27, 2014 ■ Terracon Project No. 22135032

Preventive maintenance consists of both localized maintenance (e.g. crack and joint sealing and patching) and global maintenance (e.g. surface sealing). Preventive maintenance is usually the first priority when implementing a planned pavement maintenance program and provides the highest return on investment for pavements. Prior to implementing any maintenance, additional engineering observation is recommended to determine the type and extent of preventive maintenance. Even with periodic maintenance, some movements and related cracking may still occur and repairs may be required.

4.9 Additional Design and Construction Considerations

4.9.1 Soluble Sulfate Test Results (Concrete) Samples of the soils/bedrock that will likely be in contact with project concrete were tested for soluble sulfate concentrations. The sulfate concentrations measured in the samples varied from 0.005 to 0.02 percent. According to CDOT specifications, the severity of sulfate exposure for the samples tested is Class 0. However, if there is no, or minimal cost differential, a higher level of sulfate exposure should be considered for additional sulfate resistance of construction concrete.

5.0 GENERAL COMMENTS

Terracon should be retained to review the final design plans and specifications so comments can be made regarding interpretation and implementation of our geotechnical recommendations in the design and specifications. Terracon also should be retained to provide observation and testing services during grading, excavation, foundation construction and other earth-related construction phases of the project.

The analysis and recommendations presented in this report are based upon the data obtained from the borings performed at the indicated locations and from other information discussed in this report. This report does not reflect variations that may occur between borings, across the site, or due to the modifying effects of construction, weather or time. The nature and extent of such variations may not become evident until during or after construction. If variations appear, we should be immediately notified so that further evaluation and supplemental recommendations can be provided.

The scope of services for this project does not include either specifically or by implication any environmental or biological (e.g., mold, fungi, bacteria) assessment of the site or identification or prevention of pollutants, hazardous materials or conditions. If the owner is concerned about the potential for such contamination or pollution, other studies should be undertaken.

This report has been prepared for the exclusive use of our client for specific application to the project discussed and has been prepared in accordance with generally accepted geotechnical

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Geotechnical Engineering Report N. 83rd St. & Little Thompson River Bridge ■ Boulder County, Colorado August 27, 2014 ■ Terracon Project No. 22135032

engineering practices. No warranties, either express or implied, are intended or made. Site safety, excavation support, and dewatering requirements are the responsibility of others. In the event that changes in the nature, design, or location of the project as outlined in this report are planned, the conclusions and recommendations contained in this report shall not be considered valid unless Terracon reviews the changes and either verifies or modifies the conclusions of this report in writing.

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APPENDIX A

FIELD EXPLORATION

Geotechnical Engineering Report N. 83rd St. & Little Thompson River Bridge ■ Boulder County, Colorado August 27, 2014 ■ Terracon Project No. 22135032

Field Exploration Description Seven (7) test borings were drilled at the site on November 6, 2013. An additional boring was drilled near the location of the north abutment on August 8, 2014. The borings were drilled and sampled to depths of about 10 to 40 feet at the approximate locations shown on the Boring Location Plan, Exhibit A-2. Five (5) borings were drilled near the proposed bridge structure, and three (3) borings were drilled within areas of proposed pavement construction. Borings were advanced with a CME-55 truck-mounted drilling rig, utilizing 4-inch diameter solid stem auger.

The borings were located in the field by measurements with a mechanical surveying wheel using existing site features as a reference. Right angles for locating the borings were estimated. Approximate ground surface elevations at the bridge boring locations were obtained by measurements with an engineer's level and rod from a temporary bench mark (TBM) shown on the Boring Location Plan. The accuracy of boring locations and elevations should only be assumed to the level implied by the methods used.

An engineering geologist recorded lithologic logs of each boring during the drilling operations. At selected intervals, samples of the subsurface materials were taken by means of driving a standard split-spoon or 2.5-inch O.D. California barrel sampler. Penetration resistance measurements were obtained by driving the split-spoon or California barrel into the subsurface materials with a 140- pound hammer falling 30 inches. The penetration resistance value is a useful index in estimating the consistency, relative density, or hardness of the materials encountered.

Groundwater levels were recorded in each boring shortly after completion of drilling. Due to safety considerations, the borings were backfilled following the completion of drilling operations; therefore subsequent groundwater measurements were not obtained. Some settlement of the backfill may occur over time and should be repaired as soon as possible.

A CME automatic SPT hammer was used to advance the split-spoon and/or California barrel sampler in the borings performed on this site. A greater efficiency is typically achieved with the automatic hammer compared to the conventional safety hammer operated with a cathead and rope. Published correlations between penetration values and soil properties are based on the lower efficiency cathead and rope method. This higher efficiency affects the penetration resistance blow count value by increasing the penetration per hammer blow over what would be obtained using the cathead and rope method. The effect of the automatic hammer’s efficiency has been considered in the interpretation and analysis of the subsurface information for this report.

The penetration test provides a reasonable indication of the in-place density of sandy type materials, but only provides an indication of the relative stiffness of cohesive materials since the blow count in these soils may be affected by the soils moisture content. In addition, considerable care should be exercised in interpreting penetration values in gravelly soils, particularly where the size of the gravel particle exceeds the inside diameter of the sampler.

Exhibit A-1 TB-7 TB-4A TB-6

TB-4 TB-1 TBM

TB-3 TB-2

TB-5

LEGEND: TB-X APPROXIMATE LOCATION OF BORING DRILLED ON NOVEMBER 6, 2013 OR AUGUST 8, 2014 TBM TBM = TEMPORARY BENCH MARK SURVEY MONUMENT PIN CP-NW (ELEV. = 5106.54 feet) GRAPHIC SCALE Project Manager: Project No. EXHIBIT ESW 22135032 BORING LOCATION PLAN 0’ 50’ 100’ Drawn by: Scale: EAB 1” = 100’ J-U-B ENGINEERS, INC Checked by: File Name: DIAGRAM IS FOR GENERAL LOCATION rd ESW 22135032. BLP N. 83 ST. & LITTLE THOMPSON RIVER BRIDGE REPLACEMENT ONLY, AND IS NOT INTENDED FOR A-2 CONSTRUCTION PURPOSES Approved by: Date: 1242 Bramwood Place Longmont, Colorado 80501 BOULDER COUNTY, COLORADO ESW 11/7/2013 PH. (303) 776-3921 www.terracon.com BORING LOG NO. TB-1 Page 1 of 1 PROJECT: N. 83rd St. & Little Thompson River Bridge CLIENT: J-U-B Engineers, Inc. Fort Collins, Colorado SITE: N. 83rd St. at Little Thompson River Boulder County, Colorado ATTERBERG LOCATION See Exhibit A-2 LIMITS

LL-PL-PI WATER RESULTS DRY UNIT DEPTH (Ft.)

Approximate Surface Elev: 5107.5 (Ft.) +/- FIELD TEST WEIGHT (pcf) GRAPHIC LOG CONTENT (%) WATER LEVEL LOAD, (% / psf) SAMPLE TYPE OBSERVATIONS PERCENT FINES DEPTH ELEVATION (Ft.) SWELL-CONSOL / SILTY, CLAYEY SAND (SC-SM), dark brown, brown, rust brown, very loose, fine to medium grained, micaceous

3/12" -0.1/500 14 106 23-18-5 39 5

8.0 5099.5+/- WELL GRADED SAND with SILT (SW-SM), trace fine GRAVEL, brown, red brown, loose, fine to coarse grained 9/12" 17 110 NP 10 10

12.0 5095.5+/- SAND and GRAVEL with SILT (SW-SM, GW-GM), brown, orange brown, dense, fine to coarse grained, well graded, contains occasional COBBLES 3-6-28 11 15 N=34

19.0 5088.5+/- CLAYSTONE/SILTSTONE, slightly sandy, olive-grey to 16-28-35 11 grey, hard to very hard, contains cemented lenses 20 N=63

50/2" 11 25

50/2" 30

50/2" 12 35

40.0 5067.5+/- 50/2" 11 Boring Terminated at 40 Feet 40

Stratification lines are approximate. In-situ, the transition may be gradual. Hammer Type: Automatic

Advancement Method: Notes: 4-inch Diameter Solid Flight Auger See Appendix B for description of laboratory procedures and additional data (if any). Abandonment Method: See Appendix C for explanation of symbols and Borings backfilled with soil cuttings and patched (where abbreviations. applicable) upon completion.

WATER LEVEL OBSERVATIONS Boring Started: 11/6/2013 Boring Completed: 11/6/2013 7 feet immediately after drilling Drill Rig: CME-55 Driller: EB Backfilled on 11/6/2013 1242 Bramwood Place Longmont, Colorado Project No.: 22135032 Exhibit: A-3 THIS BORING LOG IS NOT VALID SEPARATED IF THOMPSON FROM ORIGINAL REPORT. BRIDGE.GPJ 83RD-LITTLE WELL GEO SMART LOG-NO TEMPLATE 22135032.N UPDATE 8/23/14 3-31-14.GPJ BORING LOG NO. TB-2 Page 1 of 1 PROJECT: N. 83rd St. & Little Thompson River Bridge CLIENT: J-U-B Engineers, Inc. Fort Collins, Colorado SITE: N. 83rd St. at Little Thompson River Boulder County, Colorado ATTERBERG LOCATION See Exhibit A-2 LIMITS

LL-PL-PI WATER RESULTS DRY UNIT DEPTH (Ft.)

Approximate Surface Elev: 5106.0 (Ft.) +/- FIELD TEST WEIGHT (pcf) GRAPHIC LOG CONTENT (%) WATER LEVEL LOAD, (% / psf) SAMPLE TYPE OBSERVATIONS PERCENT FINES DEPTH ELEVATION (Ft.) SWELL-CONSOL / FILL, SILTY SAND with GRAVEL (SM), mixed browns, contains COBBLES or Riprap

3.0 5103+/- SILTY, CLAYEY SAND (SC-SM), dark brown, rust brown, very loose, fine to medium grained, micaceous, interbedded 3/12" 15 with SANDY SILTY CLAY (CL-ML) 5

7.0 5099+/- SAND and GRAVEL with SILT (SW-SM, GW-GM), brown, red brown, medium dense, fine to coarse grained, well graded, contains occasional COBBLES 30/12" 11 10

14.0 5092+/- CLAYSTONE/SILTSTONE, slightly sandy, grey, medium 16-13-17 11 hard to very hard, contains cemented lenses 15 N=30

32-18-14 87

50/4" 9 20

50/2" 11 25

30.0 5076+/- 50/1" 11 Boring Terminated at 30 Feet 30

Stratification lines are approximate. In-situ, the transition may be gradual. Hammer Type: Automatic

Advancement Method: Notes: 4-inch Diameter Solid Flight Auger See Appendix B for description of laboratory procedures and additional data (if any). Abandonment Method: See Appendix C for explanation of symbols and Borings backfilled with soil cuttings and patched (where abbreviations. applicable) upon completion.

WATER LEVEL OBSERVATIONS Boring Started: 11/6/2013 Boring Completed: 11/6/2013 5 feet immediately after drilling Drill Rig: CME-55 Driller: EB Backfilled on 11/6/2013 1242 Bramwood Place Longmont, Colorado Project No.: 22135032 Exhibit: A-4 THIS BORING LOG IS NOT VALID SEPARATED IF THOMPSON FROM ORIGINAL REPORT. BRIDGE.GPJ 83RD-LITTLE WELL GEO SMART LOG-NO TEMPLATE 22135032.N UPDATE 8/23/14 3-31-14.GPJ BORING LOG NO. TB-3 Page 1 of 1 PROJECT: N. 83rd St. & Little Thompson River Bridge CLIENT: J-U-B Engineers, Inc. Fort Collins, Colorado SITE: N. 83rd St. at Little Thompson River Boulder County, Colorado ATTERBERG LOCATION See Exhibit A-2 LIMITS

LL-PL-PI WATER RESULTS DRY UNIT DEPTH (Ft.)

Approximate Surface Elev: 5106.5 (Ft.) +/- FIELD TEST WEIGHT (pcf) GRAPHIC LOG CONTENT (%) WATER LEVEL LOAD, (% / psf) SAMPLE TYPE OBSERVATIONS PERCENT FINES DEPTH ELEVATION (Ft.) SWELL-CONSOL / SILTY SAND (SM), brown, fine to medium grained 2.0 5104.5+/- SANDY SILTY CLAY (CL-ML), dark brown, rust brown, very soft, micaceous, interbedded with SILTY, CLAYEY SAND (SC-SM) 1/12" 24 89 5

8.5 5098+/- WELL GRADED GRAVEL with SILT and SAND (GW-GM), 12-10-11 brown, red brown, medium dense to dense, fine to coarse 10 12 NP 8 grained, contains occasional COBBLES N=21

15.0 5091.5+/- 50/12" 20 CLAYSTONE/SILTSTONE, slightly sandy, grey, very hard, 15 contains cemented lenses

50/2" 8 20

50/2" 14 25

50/2" 13 30

35.0 5071.5+/- 50/2" 11 Boring Terminated at 35 Feet 35

Stratification lines are approximate. In-situ, the transition may be gradual. Hammer Type: Automatic

Advancement Method: Notes: 4-inch Diameter Solid Flight Auger See Appendix B for description of laboratory procedures and additional data (if any). Abandonment Method: See Appendix C for explanation of symbols and Borings backfilled with soil cuttings and patched (where abbreviations. applicable) upon completion.

WATER LEVEL OBSERVATIONS Boring Started: 11/6/2013 Boring Completed: 11/6/2013 6 feet immediately after drilling Drill Rig: CME-55 Driller: EB Backfilled on 11/6/2013 1242 Bramwood Place Longmont, Colorado Project No.: 22135032 Exhibit: A-5 THIS BORING LOG IS NOT VALID SEPARATED IF THOMPSON FROM ORIGINAL REPORT. BRIDGE.GPJ 83RD-LITTLE WELL GEO SMART LOG-NO TEMPLATE 22135032.N UPDATE 8/23/14 3-31-14.GPJ BORING LOG NO. TB-4 Page 1 of 1 PROJECT: N. 83rd St. & Little Thompson River Bridge CLIENT: J-U-B Engineers, Inc. Fort Collins, Colorado SITE: N. 83rd St. at Little Thompson River Boulder County, Colorado ATTERBERG LOCATION See Exhibit A-2 LIMITS

LL-PL-PI WATER RESULTS DRY UNIT DEPTH (Ft.)

Approximate Surface Elev: 5107.5 (Ft.) +/- FIELD TEST WEIGHT (pcf) GRAPHIC LOG CONTENT (%) WATER LEVEL LOAD, (% / psf) SAMPLE TYPE OBSERVATIONS PERCENT FINES DEPTH ELEVATION (Ft.) SWELL-CONSOL / FILL, SILTY SAND with GRAVEL (SM), brown, contains 1.5 concrete chunks 5106+/- SANDY SILTY CLAY (CL-ML), dark brown, rust brown, soft, micaceous, interbedded with SILTY, CLAYEY SAND (SC-SM) 3/12" +0.0/500 21 99 25-18-7 52 5

7.0 5100.5+/- SAND and GRAVEL with SILT (SW-SM, GW-GM), brown, red brown, rust, medium dense to dense, fine to coarse grained, well graded, contains occasional COBBLES 7-14-16 14 10 N=30

8-12-8 18 15 N=20 16.0 5091.5+/- CLAYSTONE/SILTSTONE, slightly sandy, grey, very hard, contains cemented lenses

50/3" 8 20

50/3" 11 25

34-17-17 83

30.0 5077.5+/- 50/3" 8 Boring Terminated at 30 Feet 30

Stratification lines are approximate. In-situ, the transition may be gradual. Hammer Type: Automatic

Advancement Method: Notes: 4-inch Diameter Solid Flight Auger See Appendix B for description of laboratory procedures and additional data (if any). Abandonment Method: See Appendix C for explanation of symbols and Borings backfilled with soil cuttings and patched (where abbreviations. applicable) upon completion.

WATER LEVEL OBSERVATIONS Boring Started: 11/6/2013 Boring Completed: 11/6/2013 6 feet immediately after drilling Drill Rig: CME-55 Driller: EB Backfilled on 11/6/2013 1242 Bramwood Place Longmont, Colorado Project No.: 22135032 Exhibit: A-6 THIS BORING LOG IS NOT VALID SEPARATED IF THOMPSON FROM ORIGINAL REPORT. BRIDGE.GPJ 83RD-LITTLE WELL GEO SMART LOG-NO TEMPLATE 22135032.N UPDATE 8/23/14 3-31-14.GPJ BORING LOG NO. TB-4A Page 1 of 1 PROJECT: N. 83rd St. & Little Thompson River Bridge CLIENT: J-U-B Engineers, Inc. Fort Collins, Colorado SITE: N. 83rd St. at Little Thompson River Boulder County, Colorado ATTERBERG LOCATION See Exhibit A-2 LIMITS

LL-PL-PI WATER RESULTS DRY UNIT DEPTH (Ft.)

Approximate Surface Elev: 5108.0 (Ft.) +/- FIELD TEST WEIGHT (pcf) GRAPHIC LOG CONTENT (%) WATER LEVEL LOAD, (% / psf) SAMPLE TYPE OBSERVATIONS PERCENT FINES DEPTH ELEVATION (Ft.) SWELL-CONSOL / 0.5 ASPHALT PAVEMENT, 6 inches 5107.5+/- 1.5 GRANULAR BASE, SAND with SILT and GRAVEL 5106.5+/- (SP-SM), brown, about 12 inches FILL, SILTY SAND with GRAVEL (SM), grey, tan, rust 10/12" 5 4.5 brown, loose, fine to coarse grained 5103.5+/- SILTY, CLAYEY SAND (SC-SM), dark brown, rust brown, 5 very loose, fine to medium grained, micaceous 2/12" 14

2/12" 27 23-19-4 37 10.5 5097.5+/- 10 5-8-12 SAND and GRAVEL with SILT (SW-SM, GW-GM), brown, N=20 dark brown, medium dense, fine to coarse grained, well graded, contains occasional COBBLES

5-6-7 15 15 N=13

19.0 5089+/- CLAYSTONE/SILTSTONE, slightly sandy, grey to dark 85/10" 11 grey, very hard, contains cemented lenses 20

50/1" 10 25

50/1" 9 30

35.0 5073+/- 50/1" 10 Boring Terminated at 35 Feet 35

Stratification lines are approximate. In-situ, the transition may be gradual. Hammer Type: Automatic

Advancement Method: Notes: 4-inch Diameter Solid Flight Auger See Appendix B for description of laboratory procedures and additional data (if any). Abandonment Method: See Appendix C for explanation of symbols and Borings backfilled with soil cuttings and patched upon abbreviations. completion.

WATER LEVEL OBSERVATIONS Boring Started: 8/8/2014 Boring Completed: 8/8/2014 9 feet immediately after drilling Drill Rig: CME-55 Driller: EB Backfilled on 8/8/2014 1242 Bramwood Place Longmont, Colorado Project No.: 22135032 Exhibit: A-7 THIS BORING LOG IS NOT VALID SEPARATED IF THOMPSON FROM ORIGINAL REPORT. BRIDGE.GPJ 83RD-LITTLE WELL GEO SMART LOG-NO TEMPLATE 22135032.N UPDATE 8/23/14 3-31-14.GPJ BORING LOG NO. TB-5 Page 1 of 1 PROJECT: N. 83rd St. & Little Thompson River Bridge CLIENT: J-U-B Engineers, Inc. Fort Collins, Colorado SITE: N. 83rd St. at Little Thompson River Boulder County, Colorado ATTERBERG LOCATION See Exhibit A-2 LIMITS

LL-PL-PI WATER RESULTS DRY UNIT DEPTH (Ft.) FIELD TEST WEIGHT (pcf) GRAPHIC LOG CONTENT (%) WATER LEVEL LOAD, (% / psf) SAMPLE TYPE OBSERVATIONS PERCENT FINES DEPTH ELEVATION (Ft.) SWELL-CONSOL / 0.6 ASPHALT PAVEMENT, 7 inches 1.1 GRANULAR BASE, SILTY SAND with GRAVEL (SM), brown, about 6 inches 3.0 12/12" 10 112 FILL, SILTY, CLAYEY SAND (SC-SM), with trace GRAVEL, mixed browns, loose, fine to medium grained 3/12" 14 95 22-18-4 39 SILTY, CLAYEY SAND (SC-SM), dark brown, rust brown, 5 very loose, fine to medium grained, micaceous

9.0 10.0 WELL GRADED SAND with SILT (SW-SM), trace fine 12/12" 18 GRAVEL, brown, loose, fine to coarse grained 10 Boring Terminated at 10 Feet

Stratification lines are approximate. In-situ, the transition may be gradual. Hammer Type: Automatic

Advancement Method: Notes: 4-inch Diameter Solid Flight Auger See Appendix B for description of laboratory procedures and additional data (if any). Abandonment Method: See Appendix C for explanation of symbols and Borings backfilled with soil cuttings and patched (where abbreviations. applicable) upon completion.

WATER LEVEL OBSERVATIONS Boring Started: 11/6/2013 Boring Completed: 11/6/2013 9.5 feet immediately after drilling Drill Rig: CME-55 Driller: EB Backfilled on 11/6/2013 1242 Bramwood Place Longmont, Colorado Project No.: 22135032 Exhibit: A-8 THIS BORING LOG IS NOT VALID SEPARATED IF THOMPSON FROM ORIGINAL REPORT. BRIDGE.GPJ 83RD-LITTLE WELL GEO SMART LOG-NO TEMPLATE 22135032.N UPDATE 8/23/14 3-31-14.GPJ BORING LOG NO. TB-6 Page 1 of 1 PROJECT: N. 83rd St. & Little Thompson River Bridge CLIENT: J-U-B Engineers, Inc. Fort Collins, Colorado SITE: N. 83rd St. at Little Thompson River Boulder County, Colorado ATTERBERG LOCATION See Exhibit A-2 LIMITS

LL-PL-PI WATER RESULTS DRY UNIT DEPTH (Ft.) FIELD TEST WEIGHT (pcf) GRAPHIC LOG CONTENT (%) WATER LEVEL LOAD, (% / psf) SAMPLE TYPE OBSERVATIONS PERCENT FINES DEPTH ELEVATION (Ft.) SWELL-CONSOL / 0.6 ASPHALT PAVEMENT, 7 inches 2.0 FILL, SILTY SAND with GRAVEL (SM), brown, light brown, fine to medium grained 3.0 22/12" 10 FILL, CLAYEY SAND with GRAVEL (SC), light brown, orange brown, medium dense 7/12" +0.1/200 16 112 SANDY SILTY CLAY (CL-ML), dark brown, medium stiff, 5 micaceous, interbedded with SILTY, CLAYEY SAND 7.0 (SC-SM) SAND and GRAVEL with SILT (SW-SM, GW-GM), brown, orange brown, loose to medium dense, fine to coarse grained, well graded 7/12" 10 3-4-8 13 11.5 N=12 Boring Terminated at 11.5 Feet

Stratification lines are approximate. In-situ, the transition may be gradual. Hammer Type: Automatic

Advancement Method: Notes: 4-inch Diameter Solid Flight Auger See Appendix B for description of laboratory procedures and additional data (if any). Abandonment Method: See Appendix C for explanation of symbols and Borings backfilled with soil cuttings and patched (where abbreviations. applicable) upon completion.

WATER LEVEL OBSERVATIONS Boring Started: 11/6/2013 Boring Completed: 11/6/2013 7 feet immediately after drilling Drill Rig: CME-55 Driller: EB Backfilled on 11/6/2013 1242 Bramwood Place Longmont, Colorado Project No.: 22135032 Exhibit: A-9 THIS BORING LOG IS NOT VALID SEPARATED IF THOMPSON FROM ORIGINAL REPORT. BRIDGE.GPJ 83RD-LITTLE WELL GEO SMART LOG-NO TEMPLATE 22135032.N UPDATE 8/23/14 3-31-14.GPJ BORING LOG NO. TB-7 Page 1 of 1 PROJECT: N. 83rd St. & Little Thompson River Bridge CLIENT: J-U-B Engineers, Inc. Fort Collins, Colorado SITE: N. 83rd St. at Little Thompson River Boulder County, Colorado ATTERBERG LOCATION See Exhibit A-2 LIMITS

LL-PL-PI WATER RESULTS DRY UNIT DEPTH (Ft.) FIELD TEST WEIGHT (pcf) GRAPHIC LOG CONTENT (%) WATER LEVEL LOAD, (% / psf) SAMPLE TYPE OBSERVATIONS PERCENT FINES DEPTH ELEVATION (Ft.) SWELL-CONSOL / 0.6 ASPHALT PAVEMENT, 7 inches 2.0 FILL, SILTY SAND with GRAVEL (SM), brown, light brown, fine to medium grained 7/12" +0.3/200 14 104 25-18-7 50 SANDY SILTY CLAY (CL-ML), dark brown, rust brown, very soft to medium stiff, micaceous 2/12" 13 96 5

8.0 WELL GRADED SAND with SILT (SW-SM), rust brown, 10.0 loose, fine to medium grained 9/12" 11 Boring Terminated at 10 Feet 10

Stratification lines are approximate. In-situ, the transition may be gradual. Hammer Type: Automatic

Advancement Method: Notes: 4-inch Diameter Solid Flight Auger See Appendix B for description of laboratory procedures and additional data (if any). Abandonment Method: See Appendix C for explanation of symbols and Borings backfilled with soil cuttings and patched (where abbreviations. applicable) upon completion.

WATER LEVEL OBSERVATIONS Boring Started: 11/6/2013 Boring Completed: 11/6/2013 None encountered after drilling Drill Rig: CME-55 Driller: EB Backfilled on 11/6/2013 1242 Bramwood Place Longmont, Colorado Project No.: 22135032 Exhibit: A-10 THIS BORING LOG IS NOT VALID SEPARATED IF THOMPSON FROM ORIGINAL REPORT. BRIDGE.GPJ 83RD-LITTLE WELL GEO SMART LOG-NO TEMPLATE 22135032.N UPDATE 8/23/14 3-31-14.GPJ

APPENDIX B

LABORATORY TESTING

Geotechnical Engineering Report N. 83rd St. & Little Thompson River Bridge ■ Boulder County, Colorado August 27, 2014 ■ Terracon Project No. 22135032

Laboratory Testing Samples retrieved during the field exploration were returned to the laboratory for observation by the project geotechnical engineer and were visually classified in general accordance with the Unified Soil Classification System described in Appendix C. Samples of bedrock were classified in accordance with the general notes for Rock Classification.

After sample review by the project engineer, an applicable laboratory testing program was formulated to determine engineering properties of the subsurface materials. Following completion of the laboratory testing, the field and visual descriptions were confirmed or modified as necessary, and Logs of Borings were prepared. These logs are presented in Appendix A.

Selected samples were tested for the following physical and/or engineering properties:

 Water Content  Grain Size Distribution  Dry Unit Weight  Atterberg Limits  Swell-Consolidation Potential  Water Soluble Sulfate Content

Laboratory test results are indicated on the boring logs included in Appendix A and presented in depth in Appendix B. The test results were used for the geotechnical engineering analyses and the development of foundation, pavement and earthwork recommendations. Laboratory tests were performed in general accordance with applicable local standards or other accepted standards.

Descriptive classifications of the soils indicated on the boring logs are in accordance with the enclosed General Notes and the Unified Soil Classification System. Also shown are estimated Unified Soil Classification Symbols. A brief description of this classification system is attached to this report. Classification was by visual-manual procedures. Selected samples were further classified using the results of Atterberg limit testing. The Atterberg limit test results are also provided in Appendix B.

Exhibit B-1 SWELL CONSOLIDATION TEST

10

8

6

4

2

0 AXIAL STRAIN, % STRAIN, AXIAL -2

-4

-6

-8

-10 100 1,000 10,000 105

PRESSURE, psf

Specimen Identification Classification , pcf WC, % TB-1 4.0 ft SILTY, CLAYEY SAND(SC-SM) 106 14

NOTES: Water Added to Sample at 500 psf.

PROJECT: N. 83rd St. & Little Thompson River Bridge PROJECT NUMBER: 22135032 SITE: N. 83rd St. at Little Thompson River CLIENT: J-U-B Engineers, Inc. Boulder County, Colorado Fort Collins, Colorado 1242 Bramwood Place Longmont, Colorado EXHIBIT: B-2 LABORATORY TESTS ARE NOT VALID IF SEPARATED FROM ORIGINAL REPORT. TC_CONSOL_STRAIN-USCS-NO THOMPSON BRIDGE.GPJ 83RD-LITTLE ASTM 22135032.N TERRACON2012.GDT 12/10/13 SWELL CONSOLIDATION TEST

10

8

6

4

2

0 AXIAL STRAIN, % STRAIN, AXIAL -2

-4

-6

-8

-10 100 1,000 10,000 105

PRESSURE, psf

Specimen Identification Classification , pcf WC, % TB-4 4.0 ft SANDY SILTY CLAY(CL-ML) 99 21

NOTES: Water Added to Sample at 500 psf.

PROJECT: N. 83rd St. & Little Thompson River Bridge PROJECT NUMBER: 22135032 SITE: N. 83rd St. at Little Thompson River CLIENT: J-U-B Engineers, Inc. Boulder County, Colorado Fort Collins, Colorado 1242 Bramwood Place Longmont, Colorado EXHIBIT: B-3 LABORATORY TESTS ARE NOT VALID IF SEPARATED FROM ORIGINAL REPORT. TC_CONSOL_STRAIN-USCS-NO THOMPSON BRIDGE.GPJ 83RD-LITTLE ASTM 22135032.N TERRACON2012.GDT 12/10/13 SWELL CONSOLIDATION TEST

10

8

6

4

2

0 AXIAL STRAIN, % STRAIN, AXIAL -2

-4

-6

-8

-10 100 1,000 10,000 105

PRESSURE, psf

Specimen Identification Classification , pcf WC, % TB-6 4.0 ft SANDY SILTY CLAY (CL-ML) 112 16

NOTES: Water Added to Sample at 200 psf.

PROJECT: N. 83rd St. & Little Thompson River Bridge PROJECT NUMBER: 22135032 SITE: N. 83rd St. at Little Thompson River CLIENT: J-U-B Engineers, Inc. Boulder County, Colorado Fort Collins, Colorado 1242 Bramwood Place Longmont, Colorado EXHIBIT: B-4 LABORATORY TESTS ARE NOT VALID IF SEPARATED FROM ORIGINAL REPORT. TC_CONSOL_STRAIN-USCS-NO THOMPSON BRIDGE.GPJ 83RD-LITTLE ASTM 22135032.N TERRACON2012.GDT 12/10/13 SWELL CONSOLIDATION TEST

10

8

6

4

2

0 AXIAL STRAIN, % STRAIN, AXIAL -2

-4

-6

-8

-10 100 1,000 10,000 105

PRESSURE, psf

Specimen Identification Classification , pcf WC, % TB-7 2.0 ft SANDY SILTY CLAY(CL-ML) 104 14

NOTES: Water Added to Sample at 200 psf.

PROJECT: N. 83rd St. & Little Thompson River Bridge PROJECT NUMBER: 22135032 SITE: N. 83rd St. at Little Thompson River CLIENT: J-U-B Engineers, Inc. Boulder County, Colorado Fort Collins, Colorado 1242 Bramwood Place Longmont, Colorado EXHIBIT: B-5 LABORATORY TESTS ARE NOT VALID IF SEPARATED FROM ORIGINAL REPORT. TC_CONSOL_STRAIN-USCS-NO THOMPSON BRIDGE.GPJ 83RD-LITTLE ASTM 22135032.N TERRACON2012.GDT 12/10/13 GRAIN SIZE DISTRIBUTION ASTM D422 U.S. SIEVE OPENING IN INCHES U.S. SIEVE NUMBERS HYDROMETER 4 2 1 1/2 3 6 10 16 30 50 100 200 6 3 1.5 3/4 3/8 4 8 14 20 40 60 140 100

95

90

85

80

75

70

65

60

55

50

45

40

PERCENT FINER BY WEIGHT BY FINER PERCENT 35

30

25

20

15

10

5

0 100 10 1 0.1 0.01 0.001 GRAIN SIZE IN MILLIMETERS GRAVEL SAND COBBLES SILT OR CLAY coarse fine coarse medium fine

Boring ID Depth USCS Classification LL PL PI Cc Cu TB-1 4.0 SILTY, CLAYEY SAND(SC-SM) 23 18 5 TB-1 9.0 WELL-GRADED SAND with SILT(SW-SM) NP NP NP 1.67 10.15 TB-3 9.0 WELL-GRADED GRAVEL with SILT and SAND(GW-GM) NP NP NP 1.13 73.22

Boring ID Depth D100 D60 D30 D10 %Gravel %Sand %Silt %Clay TB-1 4.0 19 0.189 4.0 57.5 38.6 TB-1 9.0 9.5 0.768 0.311 0.076 2.1 88.0 9.9 TB-3 9.0 75 9.107 1.133 0.124 50.8 41.6 7.6

PROJECT: N. 83rd St. & Little Thompson River Bridge PROJECT NUMBER: 22135032

SITE: N. 83rd St. at Little Thompson River CLIENT: J-U-B Engineers, Inc. Boulder County, Colorado Fort Collins, Colorado 1242 Bramwood Place Longmont, Colorado EXHIBIT: B-6 LABORATORY TESTS ARE NOT VALID IF SEPARATED FROM ORIGINAL REPORT. THOMPSON GRAIN SIZE: BRIDGE.GPJ 83RD-LITTLE USCS-2 22135032.N TERRACON2012.GDT 12/10/13 GRAIN SIZE DISTRIBUTION ASTM D422 U.S. SIEVE OPENING IN INCHES U.S. SIEVE NUMBERS HYDROMETER 4 2 1 1/2 3 6 10 16 30 50 100 200 6 3 1.5 3/4 3/8 4 8 14 20 40 60 140 100

95

90

85

80

75

70

65

60

55

50

45

40

PERCENT FINER BY WEIGHT BY FINER PERCENT 35

30

25

20

15

10

5

0 100 10 1 0.1 0.01 0.001 GRAIN SIZE IN MILLIMETERS GRAVEL SAND COBBLES SILT OR CLAY coarse fine coarse medium fine

Boring ID Depth USCS Classification LL PL PI Cc Cu TB-4 4.0 SANDY SILTY CLAY(CL-ML) 25 18 7 TB-5 4.0 SILTY, CLAYEY SAND(SC-SM) 22 18 4 TB-7 2.0 SANDY SILTY CLAY(CL-ML) 25 18 7

Boring ID Depth D100 D60 D30 D10 %Gravel %Sand %Silt %Clay TB-4 4.0 4.75 0.107 0.0 48.4 51.6 TB-5 4.0 9.5 0.162 1.2 59.6 39.2 TB-7 2.0 9.5 0.108 1.2 48.6 50.2

PROJECT: N. 83rd St. & Little Thompson River Bridge PROJECT NUMBER: 22135032

SITE: N. 83rd St. at Little Thompson River CLIENT: J-U-B Engineers, Inc. Boulder County, Colorado Fort Collins, Colorado 1242 Bramwood Place Longmont, Colorado EXHIBIT: B-7 LABORATORY TESTS ARE NOT VALID IF SEPARATED FROM ORIGINAL REPORT. THOMPSON GRAIN SIZE: BRIDGE.GPJ 83RD-LITTLE USCS-2 22135032.N TERRACON2012.GDT 12/10/13 GRAIN SIZE DISTRIBUTION ASTM D422 U.S. SIEVE OPENING IN INCHES U.S. SIEVE NUMBERS HYDROMETER 4 2 1 1/2 3 6 10 16 30 50 100 200 6 3 1.5 3/4 3/8 4 8 14 20 40 60 140 100

95

90

85

80

75

70

65

60

55

50

45

40

PERCENT FINER BY WEIGHT BY FINER PERCENT 35

30

25

20

15

10

5

0 100 10 1 0.1 0.01 0.001 GRAIN SIZE IN MILLIMETERS GRAVEL SAND COBBLES SILT OR CLAY coarse fine coarse medium fine

Boring ID Depth USCS Classification LL PL PI Cc Cu STREAMBED 1.5 POORLY GRADED SAND with GRAVEL(SP) NP NP NP 0.94 5.20

Boring ID Depth D100 D60 D30 D10 %Gravel %Sand %Silt %Clay STREAMBED 1.5 100 1.675 0.713 0.322 18.1 77.6 0.9

PROJECT: N. 83rd St. & Little Thompson River Bridge PROJECT NUMBER: 22135032

SITE: N. 83rd St. at Little Thompson River CLIENT: J-U-B Engineers, Inc. Boulder County, Colorado Fort Collins, Colorado 1242 Bramwood Place Longmont, Colorado EXHIBIT: B-8 LABORATORY TESTS ARE NOT VALID IF SEPARATED FROM ORIGINAL REPORT. THOMPSON GRAIN SIZE: BRIDGE.GPJ 83RD-LITTLE USCS-2 22135032.N TERRACON2012.GDT 12/10/13 GRAIN SIZE DISTRIBUTION ASTM D422 U.S. SIEVE OPENING IN INCHES U.S. SIEVE NUMBERS HYDROMETER 4 2 1 1/2 3 6 10 16 30 50 100 200 6 3 1.5 3/4 3/8 4 8 14 20 40 60 140 100

95

90

85

80

75

70

65

60

55

50

45

40

PERCENT FINER BY WEIGHT BY FINER PERCENT 35

30

25

20

15

10

5

0 100 10 1 0.1 0.01 0.001 GRAIN SIZE IN MILLIMETERS GRAVEL SAND COBBLES SILT OR CLAY coarse fine coarse medium fine

Boring ID Depth USCS Classification LL PL PI Cc Cu TB-2 17.0 CLAYSTONE/SILTSTONE 32 18 14 TB-4 27.0 CLAYSTONE/SILTSTONE 34 17 17

Boring ID Depth D100 D60 D30 D10 %Gravel %Sand %Silt %Clay TB-2 17.0 2 0.017 0.002 0.0 13.0 43.5 43.5 TB-4 27.0 2 0.0 17.1 82.9

PROJECT: N. 83rd St. & Little Thompson River Bridge PROJECT NUMBER: 22135032

SITE: N. 83rd St. at Little Thompson River CLIENT: J-U-B Engineers, Inc. Boulder County, Colorado Fort Collins, Colorado 1242 Bramwood Place Longmont, Colorado EXHIBIT: B-9 LABORATORY TESTS ARE NOT VALID IF SEPARATED FROM ORIGINAL REPORT. THOMPSON GRAIN SIZE: BRIDGE.GPJ 83RD-LITTLE USCS-2 22135032.N TERRACON2012.GDT 12/10/13 GRAIN SIZE DISTRIBUTION ASTM D422 U.S. SIEVE OPENING IN INCHES U.S. SIEVE NUMBERS HYDROMETER 4 2 1 1/2 3 6 10 16 30 50 100 200 6 3 1.5 3/4 3/8 4 8 14 20 40 60 140 100

95

90

85

80

75

70

65

60

55

50

45

40

PERCENT FINER BY WEIGHT BY FINER PERCENT 35

30

25

20

15

10

5

0 100 10 1 0.1 0.01 0.001 GRAIN SIZE IN MILLIMETERS GRAVEL SAND COBBLES SILT OR CLAY coarse fine coarse medium fine

Boring ID Depth USCS Classification LL PL PI Cc Cu TB-4A 9.0 SILTY, CLAYEY SAND(SC-SM) 23 19 4

Boring ID Depth D100 D60 D30 D10 %Gravel %Sand %Silt %Clay TB-4A 9.0 9.5 0.164 0.8 62.3 36.8

PROJECT: N. 83rd St. & Little Thompson River Bridge PROJECT NUMBER: 22135032

SITE: N. 83rd St. at Little Thompson River CLIENT: J-U-B Engineers, Inc. Boulder County, Colorado Fort Collins, Colorado 1242 Bramwood Place Longmont, Colorado EXHIBIT: B-10 LABORATORY TESTS ARE NOT VALID IF SEPARATED FROM ORIGINAL REPORT. THOMPSON GRAIN SIZE: BRIDGE.GPJ 83RD-LITTLE USCS-2 22135032.N TERRACON2012.GDT 8/23/14

APPENDIX C

SUPPORTING DOCUMENT GENERAL NOTES DESCRIPTION OF SYMBOLS AND ABBREVIATIONS

Water Initially (HP) Hand Penetrometer Encountered Water Level After a (T) Torvane Auger Split Spoon Specified Period of Time

Water Level After a Specified Period of Time (b/f) Standard Penetration Test (blows per foot) Shelby Tube Macro Core Water levels indicated on the soil boring (PID) Photo-Ionization Detector logs are the levels measured in the borehole at the times indicated. (OVA) Organic Vapor Analyzer

SAMPLING Groundwater level variations will occur Ring Sampler Rock Core over time. In low permeability soils, FIELD TESTS WATER LEVEL accurate determination of groundwater levels is not possible with short term water level observations. Grab Sample No Recovery

DESCRIPTIVE SOIL CLASSIFICATION Soil classification is based on the Unified Soil Classification System. Coarse Grained Soils have more than 50% of their dry weight retained on a #200 sieve; their principal descriptors are: boulders, cobbles, gravel or sand. Fine Grained Soils have less than 50% of their dry weight retained on a #200 sieve; they are principally described as clays if they are plastic, and silts if they are slightly plastic or non-plastic. Major constituents may be added as modifiers and minor constituents may be added according to the relative proportions based on grain size. In addition to gradation, coarse-grained soils are defined on the basis of their in-place relative density and fine-grained soils on the basis of their consistency.

LOCATION AND ELEVATION NOTES Unless otherwise noted, Latitude and Longitude are approximately determined using a hand-held GPS device. The accuracy of such devices is variable. Surface elevation data annotated with +/- indicates that no actual topographical survey was conducted to confirm the surface elevation. Instead, the surface elevation was approximately determined from topographic maps of the area.

RELATIVE DENSITY OF COARSE-GRAINED CONSISTENCY OF FINE-GRAINED SOILS BEDROCK SOILS (More than 50% retained on No. 200 sieve.) (50% or more passing the No. 200 sieve.) Density determined by Consistency determined by laboratory shear strength testing, Standard Penetration Resistance field visual-manual procedures or standard penetration Includes gravels, sands and silts. resistance Standard Standard Standard Ring Descriptive Unconfined Ring Ring Descriptive Penetration or Penetration or Penetration or Descriptive Sampler Term Compressive Sampler Sampler Term N-Value N-Value N-Value Term Blows/Ft. (Consistency) Strength, Blows/Ft. Blows/Ft. (Density) Blows/Ft. Blows/Ft. Blows/Ft. (Consistency) Qu, psf

Very Loose 0 - 3 0 - 5 Very Soft less than 500 0 - 1 < 3 < 24 < 20 Weathered

Loose 4 - 9 6 - 14 Soft 500 to 1,000 2 - 4 3 - 5 24 - 35 20 - 29 Firm

Medium Dense 10 - 29 15 - 46 Medium-Stiff 1,000 to 2,000 4 - 8 6 - 10 36 - 60 30 - 49 Medium Hard

STRENGTH TERMS Dense 30 - 50 47 - 79 Stiff 2,000 to 4,000 8 - 15 11 - 18 61 - 96 50 - 79 Hard

Very Dense > 50 >_ 80 Very Stiff 4,000 to 8,000 15 - 30 19 - 36 > 96 >79 Very Hard

Hard > 8,000 > 30 > 36

RELATIVE PROPORTIONS OF SAND AND GRAVEL GRAIN SIZE TERMINOLOGY

Descriptive Term(s) Percent of Major Component Particle Size of other constituents Dry Weight of Sample Trace < 15 Boulders Over 12 in. (300 mm) With 15 - 29 Cobbles 12 in. to 3 in. (300mm to 75mm) Modifier > 30 Gravel 3 in. to #4 sieve (75mm to 4.75 mm) Sand #4 to #200 sieve (4.75mm to 0.075mm Silt or Clay Passing #200 sieve (0.075mm) RELATIVE PROPORTIONS OF FINES PLASTICITY DESCRIPTION Descriptive Term(s) Percent of Term Plasticity Index of other constituents Dry Weight Non-plastic 0 Trace < 5 Low 1 - 10 With 5 - 12 Medium 11 - 30 Modifier > 12 High > 30

Exhibit C-1 UNIFIED SOIL CLASSIFICATION SYSTEM Soil Classification A Criteria for Assigning Group Symbols and Group Names Using Laboratory Tests Group B Group Name Symbol    E F Gravels: Clean Gravels: Cu 4 and 1 Cc 3 GW Well-graded gravel C E F More than 50% of Less than 5% fines Cu  4 and/or 1  Cc  3 GP Poorly graded gravel F,G,H coarse fraction retained Gravels with Fines: Fines classify as ML or MH GM Silty gravel C Coarse Grained Soils: on No. 4 sieve More than 12% fines Fines classify as CL or CH GC Clayey gravel F,G,H More than 50% retained    E SW Well-graded sand I on No. 200 sieve Sands: Clean Sands: Cu 6 and 1 Cc 3 D E I 50% or more of coarse Less than 5% fines Cu  6 and/or 1  Cc  3 SP Poorly graded sand G,H,I fraction passes No. 4 Sands with Fines: Fines classify as ML or MH SM Silty sand D sieve More than 12% fines Fines classify as CL or CH SC Clayey sand G,H,I PI  7 and plots on or above “A” line J CL Lean clay K,L,M Inorganic: J K,L,M Silts and Clays: PI  4 or plots below “A” line ML Silt Liquid limit less than 50 Liquid limit - oven dried Organic clay K,L,M,N Organic:  0.75 OL Fine-Grained Soils: Liquid limit - not dried Organic silt K,L,M,O 50% or more passes the PI plots on or above “A” line CH Fat clay K,L,M No. 200 sieve Inorganic: K,L,M Silts and Clays: PI plots below “A” line MH Elastic Silt Liquid limit 50 or more Liquid limit - oven dried Organic clay K,L,M,P Organic:  0.75 OH Liquid limit - not dried Organic silt K,L,M,Q Highly organic soils: Primarily organic matter, dark in color, and organic odor PT Peat

A Based on the material passing the 3-inch (75-mm) sieve H If fines are organic, add “with organic fines” to group name. B If field sample contained cobbles or boulders, or both, add “with cobbles I If soil contains  15% gravel, add “with gravel” to group name. or boulders, or both” to group name. J If Atterberg limits plot in shaded area, soil is a CL-ML, silty clay. C Gravels with 5 to 12% fines require dual symbols: GW-GM well-graded K If soil contains 15 to 29% plus No. 200, add “with sand” or “with gravel,” gravel with silt, GW-GC well-graded gravel with clay, GP-GM poorly whichever is predominant. graded gravel with silt, GP-GC poorly graded gravel with clay. L If soil contains  30% plus No. 200 predominantly sand, add “sandy” to D Sands with 5 to 12% fines require dual symbols: SW-SM well-graded group name. sand with silt, SW-SC well-graded sand with clay, SP-SM poorly graded M If soil contains  30% plus No. 200, predominantly gravel, add sand with silt, SP-SC poorly graded sand with clay “gravelly” to group name. 2 N  (D ) PI 4 and plots on or above “A” line. E 30 O Cu = D60/D10 Cc = PI  4 or plots below “A” line. P D10 x D60 PI plots on or above “A” line. Q F PI plots below “A” line. If soil contains  15% sand, add “with sand” to group name.

G If fines classify as CL-ML, use dual symbol GC-GM, or SC-SM.

Exhibit C-2 ROCK CLASSIFICATION (Based on ASTM C-294)

Sedimentary Rocks

Sedimentary rocks are stratified materials laid down by water or wind. The sediments may be composed of particles or pre-existing rocks derived by mechanical weathering, evaporation or by chemical or organic origin. The sediments are usually indurated by cementation or compaction.

Chert Very fine-grained siliceous rock composed of micro-crystalline or cyrptocrystalline quartz, chalcedony or opal. Chert is various colored, porous to dense, hard and has a conchoidal to splintery fracture.

Claystone Fine-grained rock composed of or derived by erosion of silts and clays or any rock containing clay. Soft massive and may contain carbonate minerals.

Conglomerate Rock consisting of a considerable amount of rounded gravel, sand and cobbles with or without interstitial or cementing material. The cementing or interstitial material may be quartz, opal, calcite, dolomite, clay, iron oxides or other materials.

Dolomite A fine-grained carbonate rock consisting of the mineral dolomite [CaMg(CO3)2]. May contain noncarbonate impurities such as quartz, chert, clay minerals, organic matter, gypsum and sulfides. Reacts with hydrochloric acid (HCL).

Limestone A fine-grained carbonate rock consisting of the mineral calcite (CaCO3). May contain noncarbonate impurities such as quartz, chert, clay minerals, organic matter, gypsum and sulfides. Reacts with hydrochloric acid (HCL).

Sandstone Rock consisting of particles of sand with or without interstitial and cementing materials. The cementing or interstitial material may be quartz, opal, calcite, dolomite, clay, iron oxides or other material.

Shale Fine-grained rock composed of or derived by erosion of silts and clays or any rock containing clay. Shale is hard, platy, or fissile and may be gray, black, reddish or green and may contain some carbonate minerals (calcareous shale).

Siltstone Fine grained rock composed of or derived by erosion of silts or rock containing silt. Siltstones consist predominantly of silt sized particles (0.0625 to 0.002 mm in diameter) and are intermediate rocks between claystones and sandstones and may contain carbonate minerals.

Exhibit C-3

Final Report

Little Thompson River Hydrologic Analysis

Phase 2: Little Thompson River above Big Thompson River

Prepared for Colorado Department of Transportation

June 10, 2015

9191 S. Jamaica Street Englewood, CO 80112

Contents

Section Page Acronyms and Abbreviations ...... v Executive Summary ...... ES‐1 1.0 Purpose and Objective ...... 1‐1 1.1 Background ...... 1‐1 1.2 Project Area Description ...... 1‐1 1.3 Effective Flood Insurance Studies ...... 1‐1 1.4 Mapping ...... 1‐2 1.5 Data Collection ...... 1‐2 1.6 Flood History ...... 1‐3 1.6.1 Historic Flood Events ...... 1‐3 1.6.2 September 2013 ...... 1‐3 2.0 Hydrologic Analyses ...... 2‐1 2.1 Previous Studies ...... 2‐1 2.1.1 Hydrology Studies for the Big Thompson River and Little Thompson River (USACE, 1974) ...... 2‐1 2.1.2 Floodplain Information. Report Little Thompson River. Boulder and Larimer Counties (USACE, 1977a) ...... 2‐1 2.1.3 Summary of Hydrologic Analysis, Little Thompson River, Larimer County Colorado, Flood Insurance Study/Map Revision. Technical Support Data Notebook (Ayres, 2010) ...... 2‐2 2.1.4 Little Thompson River Hydrology Analysis – I‐25 Frontage Road Mile Marker 249.847, Weld County, Colorado (CDOT, 2011) ...... 2‐2 2.1.5 Little Thompson River Hydrology Analysis – Report of September 2013 Little Thompson River Flooding (CDWR Dam Safety, 2014) ...... 2‐3 2.1.6 Little Thompson River Hydrologic Analysis [Phase I] (CH2M HILL, 2014) ...... 2‐3 2.2 Stream Gage Analysis ...... 2‐3 2.3 Peak Discharge Estimates ...... 2‐4 2.4 Rainfall‐Runoff Modeling ...... 2‐6 2.4.1 Overall Modeling Approach ...... 2‐6 2.4.2 Summary of Modeling Approaches Considered ...... 2‐6 2.4.3 Basin Delineation ...... 2‐7 2.4.4 Basin Characterization ...... 2‐7 2.4.5 Model Development ...... 2‐8 2.4.6 Model Calibration ...... 2‐11 2.4.7 Predictive Model Implementation ...... 2‐13 3.0 Hydrologic Model Results ...... 3‐1 3.1 Estimate of Design Flow Magnitudes ...... 3‐1 3.2 Comparison to Previous Hydrologic Studies ...... 3‐2 3.2.1 Previous Hydrologic Studies Calibrated to September 2013 Event ...... 3‐2 3.2.2 Previous Predictive Hydrologic Studies ...... 3‐2 4.0 Conclusions and Recommendations ...... 4‐1 4.1 Design Peak Discharge Magnitudes ...... 4‐1 4.2 Assessment of September 2013 Event ...... 4‐2 5.0 References ...... 5‐1

WT0213151026BOI III CONTENTS, CONTINUED

Tables ES‐1 Little Thompson River Comparison of Modeled Discharges to Observed Discharges ES‐2 Estimate of the Recurrence Interval of the September 2013 Event 1 Data Collected for the Little Thompson River 2 Discharge‐Frequency Based on Flood Frequency Analysis of Gage Record 3 Little Thompson Physical‐Based Peak Discharge Observations 4 Depth‐Area Reduction Factors 5 Little Thompson River Comparison of Modeled Discharges to Observed Discharges 6 Comparison of Modeled Time‐to‐Peak to Observed Time‐to‐Peak 8 Little Thompson River Modeled 10‐,4,‐2,‐1, and 0.2‐Percent Chance Unit Peak Discharge 9 Calibrated Model Comparison 10 Comparison of Modeled 1 Percent Annual Chance Flow to Other Estimates 11 Proposed 10, 4, 2, 1, and 0.2 Percent Chance Peak Discharge 12 Estimate of the Recurrence Interval of the September 2013 Event Tables – Appendix B B‐1 24‐Hour Little Thompson Models: Hydrologic Zone, Subbasin Area, and Curve Number (CN) B‐2 Little Thompson River Rainfall Depths at Subbasin Centroids B‐3 5‐Minute Dimensionless 24‐Hr NRCS Type II Cumulative Rainfall Distribution B‐4 24‐Hour Little Thompson Models: Unit Hydrograph Parameters B‐5 24‐Hour Little Thompson Models: Routing Reach Parameters B‐6 Little Thompson River Land Use Conditions B‐7 Little Thompson River Proposed Model Results Summary Figures ES‐1 Little Thompson River Overview Map ES‐2 Little Thompson River Peak Discharge Profiles 1 Vicinity and Watershed Map 2 Little Thompson River Peak Discharge Estimate and Gage Locations 3 Phase 2 Connectivity Map 4 Phase 2 AWA 10‐Day Precipitation 5 NRCS 24‐Hour Type II Unit Hyetograph 6 24‐Hour Depth‐Area Reduction Factor (DARF) Curves 7 Phase 2 Land Use Map 8 Phase 2 Soils Map 9 Phase 2 Muskingum‐Cunge Eight‐Point Routing Cross Sections 10 Little Thompson September 2013 Rainfall 11 Hydrographs at Key Design Locations 12 Little Thompson River Peak Discharge Profiles 13 Comparison of Little Thompson River 1 Percent Chance Discharge Estimates vs. Drainage Area 14 1 Percent Annual Chance Peak Unit Discharge versus Subbasin Area Appendices A FEMA Information B Hydrologic Analysis and Parameters C Ayres Associates Flood Frequency Analysis D Project Correspondence and Response to Review Comments E September 2013 Peak Discharge Estimates Documentation F Drainage Area Reduction Factor Documentation G Digital Data (electronic only)

IV WT0213151026BOI

Acronyms and Abbreviations

AMC Antecedent Moisture Condition AWA Applied Weather Associates CDOT Colorado Department of Transportation CDWR Colorado Division of Water Resources cfs cubic feet per second CN curve number CWCB Colorado Water Conservation Board DARF depth‐Area reduction factor FEMA Federal Emergency Management Agency FIRM Flood Insurance Rate Map FIS Flood Insurance Study GIS geographic information system HEC‐HMS Hydrologic Engineering Center’s Hydrologic Modeling System I‐25 Interstate 25 LiDAR Light Detection and Ranging LULC Land Use and Land Cover NED National Elevation Dataset NOAA National Oceanic and Atmospheric Administration NRCS Natural Resources Conservation Service PMR Physical Map Revision QC quality control SCS Soil Conservation Service SH State Highway SPAS Storm Precipitation Analysis System US 36 U.S. Route 36 USACE U.S. Army Corps of Engineers USDA U.S. Department of Agriculture USGS U.S. Geological Survey

WT0213151026BOI V

I hereby affirm that this report and hydrologic analysis for the Little Thompson River was prepared by me, or under my direct supervision, for the owners thereof, in accordance with the current provisions of the Colorado Floodplain and Stormwater Criteria Manual, and approved variances and exceptions thereto.

Signature:

CH2M HILL June 10, 2015 Morgan Lynch, P.E. Registered Professional Engineer State of Colorado No. 44653 (seal)

This Document Prepared by: Management Review Preparation Team Technical Support Cory Hooper, PE Morgan Lynch, PE Brad Bettag, PE CH2M HILL CH2M HILL CH2M HILL Water Resources Engineer Water Resources Engineer Water Resources Engineer Doug Stewart, PE Christina McDonough, PE Luke Heyerdahl CH2M HILL CH2M HILL CH2M HILL Transportation Technologist Water Resources Engineer Water Information Professional Management Specialist James Woidt, PE Tim Eversoll, PE CH2M HILL Bill Kappel CH2M HILL Water Resources Engineer Applied Weather Associates Manager – Transportation President/ Chief Meteorologist Engineer John Hunt, PE Ayres Associates Manager – Senior Hydraulic Engineer

WT0213151026BOI VII

Executive Summary

In late summer 2013, the Colorado Front Range experienced an extensive rainstorm event spanning approximately 10 days from September 8 to September 18. The event generated widespread flooding as the long‐duration storm saturated soils and increased runoff potential. Flooding resulted in substantial erosion, bank widening, and realigning of stream channels; transport of mud, rock, and debris; failures of dams; landslides; damage to roads, bridges, utilities, and other public infrastructures; and flood impacts to many residential and commercial structures. Ten fatalities were attributed to the floods. During and immediately following the rainstorm event, the Colorado Department of Transportation (CDOT) engaged in a massive flood response effort to protect the traveling public, rebuild damaged roadways and bridges to get critical travel corridors open again, and engage in assessments and analyses to guide longer‐ term rebuilding efforts. As part of this effort, CDOT partnered with the Colorado Water Conservation Board (CWCB) to initiate hydrologic analyses in several key river systems impacted by the floods. The work was contracted to three consultant teams led by the following firms: Boulder Creek, Little Thompson River CH2M HILL Big Thompson River, St. Vrain Creek, Lefthand Creek Jacobs Coal Creek, South Platte River URS The purpose of the analyses is to ascertain the approximate magnitude of the September flood event in key locations throughout the watershed and to prepare estimates of peak discharge that can serve to guide the design of permanent roadway and other infrastructure improvements along the impacted streams. These estimates of peak discharges for various return periods will be shared with local floodplain administrators for their consideration in revising or updating any current regulatory discharges. The primary tasks of the hydrologic analyses include: 1. Estimate peak discharges that were believed to have occurred during the flood event at key locations along the study streams. Summarize theses discharge along with estimates provided by others in comparison to existing regulatory discharges. Document the approximate return period associated with the September flood event based on current regulatory discharges. 2. Prepare rainfall‐runoff models of the study watersheds, input available rainfall data representing the September rainstorm, and calibrate results to provide correlation to estimated peak discharges. 3. Prepare updated flood frequency analyses using available gage data and incorporate the estimated peak discharges from the September event. 4. Use rainfall‐runoff models to estimate predictive peak discharges for a number of return periods based on rainfall information published by the National Oceanic and Atmospheric Administration (NOAA) (NOAA Atlas 14, Volume 8, Updated 2013; NOAA, 2013a). Compare results to updated flood frequency analyses and unit discharge information, and calibrate as appropriate. The hydrologic analyses were divided into two phases of work. Phase 1 focused on the mountainous areas in the upper portion of the watersheds, extending from the upper divides of the Big Thompson River, Little Thompson River, St. Vrain Creek, Lefthand Creek, Coal Creek, and Boulder Creek watersheds to the mouth of their respective canyons. The Phase 1 analyses have been documented in six reports with the following titles and dates: 1. Hydrologic Evaluation of the Big Thompson Watershed, August 2014 2. Little Thompson River Hydrologic Analysis Final Report, August 2014 3. Hydrologic Evaluation of the St. Vrain Watershed, August 2014 4. Hydrologic Evaluation of the Lefthand Creek Watershed, August 2014, revised December 2014

WT0213151026BOI ES-1 EXECUTIVE SUMMARY

5. Coal Creek Hydrology Evaluation, August 2014 6. Boulder Creek Hydrologic Evaluation Final Report, August 2014 Copies of these Phase 1 reports can be downloaded from the CWCB website at the following link: http://cwcb.state.co.us/water‐management/flood/pages/2013floodresponse.aspx Phase 2 of the hydrologic analyses focused on the plains region of the Big Thompson River, Boulder Creek, Little Thompson River, and St. Vrain Creek from the downstream limit of the Phase 1 studies at the mouth of the canyons to the downstream confluences of the watersheds with their respective receiving streams. The hydrologic analyses were contracted to two consultant teams led by the following firms: Boulder Creek, Little Thompson River CH2M HILL Big Thompson River, St. Vrain Creek Jacobs Phase 2 hydrologic analyses for each of the watersheds included flows from the original Phase 1 watersheds, as appropriate: the downstream reach of the Big Thompson River was modeled to include flows from the Little Thompson River. Likewise, the downstream reach of St. Vrain Creek included flows from Lefthand Creek and Boulder Creek, with Boulder Creek in turn receiving flows from Coal Creek. This report documents the Phase 2 hydrologic evaluation for the Little Thompson River. As part of the evaluation, CH2M HILL developed a rainfall‐runoff model to transform the recorded rainfall to stream discharge using the U.S. Army Corps of Engineers’ (USACE’s) Hydrologic Engineering Center’s Hydrologic Modeling System (HEC‐HMS) hydrologic model. The hydrologic model was calibrated through adjustment sof model input values that represent land cover and soil conditions. The calibration of these parameters is common because they take into account vegetative cover, soil structure, topography, land use history, and other considerations that are not easily accessible using aerial imagery. The extent of the Little Thompson River Watershed study area and physical‐based observation locations is presented in Figure ES‐1. A comparison of observed discharges and the discharges of the calibrated model is presented in Table ES‐1.

TABLE ES‐1 Little Thompson River Comparison of Modeled Discharges to Observed Discharges Site HMS Drainage Area Observed Peak Modeled Peak % Number Node Location (square miles) Discharge (cfs) Discharge (cfs) Difference

N/A LT‐J6 Little Thompson River at X Bar 7 81.8 15,731 14,300 ‐9% Ranch

LT‐2 LT‐J10 Little Thompson River at South 132.1 13,400 15,500 16% County Line Road

LT‐3 LT‐J12 Little Thompson River at 165.9 15,700 15,200 ‐3% Interstate 25

LT‐4 LT‐J13 Little Thompson River at County 186.5 18,000a 14,900 ‐17% Road 17

a Bridge overtopped (URS, 2015).

The calibrated model was modified to estimate the 10, 4, 2, 1, and 0.2 percent annual chance peak discharges (10‐, 25‐, 50‐, 100‐, and 500‐year events, respectively, for purposes of this Executive Summary1)

1 While the term “100‐year event” and similar terminology are used in this Executive Summary to better relate the magnitude of the September 2013 event to the general public, it is not an event that occurs explicitly once every 100 years, but rather an event that has a 1 percent chance of occurring in any given year. Thus, a 100‐year event could happen in back‐to‐back years, or not at all for 200 years. For this reason, the current FEMA standard is to refer to the “100‐year event” as the “1‐percent annual chance event” and it is important for the reader to note that the labeling of the September 2013 event as a 50‐year event, or other recurrence interval, does not preclude the future occurrence of a similar, or greater, flood in the that corresponding timeframe.

ES-2 WT0213151026BOI EXECUTIVE SUMMARY based on a 24‐hour Soil Conservation Service (SCS, now the Natural Resources Conservation Service [NRCS]) Type II Storm and recently released 2014 NOAA Atlas 14 rainfall values (NOAA, 2014). The modeled discharges were then compared to previous and concurrent alternative estimates of annual chance peak discharges. The assumptions and limitations of the various methodologies were closely reviewed, compared, and contrasted. The predictive model developed as part of the current study is proposed as the appropriate model to revise high‐flow hydrology along the Little Thompson River downstream of U.S. Route 36 (US 36) to the confluence with the Big Thompson River. These recommended values are shown in Table ES‐2 and provided graphically in Figure ES‐2. With this recommendation, the peak discharges observed along the Little Thompson River during the September 2013 storm event had an estimated recurrence intervals between the 2 percent annual chance peak discharge, or a r50 ‐yea storm event, and the 0.2 percent annual chance peak discharge, or a 500‐year storm event.

TABLE ES‐2 Estimate of the Recurrence Interval of the September 2013 Event Predictive Annual Chance Peak Discharge (cfs)

Estimated Recurrence Observed Interval Location Discharge (cfs) 10 percent 4 percent 2 percent 1 percent 0.2 percent (yr)

Little Thompson River at 15,731a 2,310 4,500 6,970 10,200 20,700 100 to 500 X Bar 7 Ranch

Little Thompson River at 15,500b 2,760 5,380 8,330 12,100 24,700 100 to 500 LTCANYO Gage

Little Thompson River at 13,400c 3,650 6,940 10,600 15,300 30,800 50 to 100 South County Line Road

Little Thompson River at 15,700c 4,140 7,090 10,900 16,000 33,500 100 Interstate 25

Little Thompson River at 18,000c 4,480 7,150 10,700 15,700 32,100 100 to 500 County Road 17

Little Thompson River 14,700b 4,450 7,130 10,500 15,400 31,400 100 Upstream of Confluence with Big Thompson a Per CDWR, 2014. b Per Calibrated Hydrologic Model. c Per URS, 2015.

WT0213151026BOI ES-3 VICINITY MAP

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CDOT Flood Recovery Hydrologic Evaluation

UNK \\GECKO\GROUPS\TBG\481085-482330 CDOT EMERGENCY RESPONSE SERVICES\390_DESIGN_ELEMENTS\DRAINAGE\GIS_PHASE_II\MAPFILES\REPORT\FIGUREES1_LITTLETHOMPSONOVERVIEWMAP.MXD BBETTAG 2/10/2015 9:21:45 AM Table 2.4 Phase I Modeled Little Thompson River Discharges [CDOT/CH2MHill 2014].

Drainage Peak Discharge (CFS) Location Area Notes 10-year 25-year 50-year 100-year 500-year (sq mi) At U.S. Highway 36 Point located approx. 13 43.8 651 1,376 2,264 3,455 7,600 near Pinewood Springs miles U/S of 83rd Str. Notes: U/S = Upstream

CDOT initiated the Phase I hydrology study starting in late 2013. Preliminary data became available in the spring of 2014; final draft data was published in June of 2014; and the final report delivered in August of 2014. In the Phase II hydrology study CDOT continued the analyses from the canyons across the plains (including the current 83rd Street study reach) to the confluences of each watershed.

2.3.2 Phase II: Plains - Canyon Mouth to Confluence

The Phase II Little Thompson River hydrology study was started in the late summer of 2014 and was completed in June of 2015 with the publication of a report titled “Little Thompson River Hydrologic Analysis Phase 2: Little Thompson River above Big Thompson River” [CH2MHill, FINAL June 10, 2015] (See Appendix 1.3.2). Discharges upstream and downstream of the current study reach from the Phase II study are shown in Table 2.5. The selected discharges for the FOR design of the 83rd Street Bridge were interpolated from the Phase 2 report’s graphical discharge profile as shown in Figure 2.1 and presented in Table 2.5. Additional discharges (2-, 5-, 25-, and 200-year) needed for the design of the 83rd Street Bridge were interpolated as shown in Appendix 1.3.3.

Table 2.5 Phase II Modeled Little Thompson River Discharges [CDOT/CH2MHill 2015].

Drainage Peak Discharge (CFS) Location Area Notes 10-year 25-year 50-year 100-year 500-year (sq mi) At U.S. Hwy. 36 near 43.8 660 1,380 2,270 3,460 7,600 Approx. 13 mi. U/S of 83rd Str. Pinewood Springs X Bar 7 Ranch 81.8 2,310 4,500 6,970 10,200 20,700 LTCANYO Gage 100.2 2,760 5,380 8,330 12,100 24,700 Approx. 2.7 mi. U/S of 83rd Str. Selected Design Discharges 83rd Str./LCR 23E ~108 3,100 --- 9,100 13,000 26,600 Interpolated from Figure 2.1 S. County Line Rd./ 132.1 3,650 6,940 10,600 15,300 30,800 Approx. 6.8 mi. D/S of 83rd Str. (Larimer-Weld) Interstate 25 165.9 4,140 7,090 10,900 16,000 33,500 Note: Data were compiled from Tables ES-1, ES-2, 11, and 12 in the Final Phase 2 Report. U/S = Upstream and D/S = Downstream.

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Figure 2.1 Little Thompson River Peak Discharge Profiles [CDOT/CH2M Hill 2015] and Selected Design Discharges

ATTACHMENT B PRE-PROJECT

HY-8 Culvert Analysis Report Crossing Front View (Roadway Profile): Pre-Project

Crossing Discharge Data Discharge Selection Method: Specify Minimum, Design, and Maximum Flow Minimum Flow: 850 cfs Design Flow: 1400 cfs Maximum Flow: 13000 cfs Tailwater Channel Data - Pre-Project Tailwater Channel Option: Irregular Channel Channel Slope: 0.0045 User Defined Channel Cross-Section: Coord No. Station (ft) Elevation (ft) Manning's n 1 0.00 5096.40 0.0350 2 13.00 5096.00 0.0350 3 113.69 5094.10 0.0350 4 141.60 5093.75 0.0350 5 168.20 5093.67 0.0350 6 192.70 5093.52 0.0350 7 223.10 5093.33 0.0350 8 253.60 5092.44 0.0350 9 282.50 5091.07 0.0350 10 310.20 5089.65 0.0350 11 349.70 5087.64 0.0350 12 370.00 5085.00 0.0350 13 443.00 5085.00 0.0350 14 445.00 5088.32 0.0350 15 495.80 5090.91 0.0350 16 524.70 5090.96 0.0350 17 551.00 5090.86 0.0350 18 577.20 5090.81 0.0350 19 605.70 5090.18 0.0350 20 632.50 5090.56 0.0350 21 727.10 5092.00 0.0350 22 742.20 5093.00 0.0350 23 747.50 5094.00 0.0350 24 751.60 5095.00 0.0350 25 755.90 5096.00 0.0350 26 760.70 5097.00 0.0350 27 765.70 5098.00 0.0350 28 785.69 5098.50 0.0000

Roadway Data for Crossing: Pre-Project Roadway Profile Shape: Constant Roadway Elevation Crest Length: 50.00 ft Crest Elevation: 5091.50 ft Roadway Surface: Paved Roadway Top Width: 28.00 ft

Culvert Data Summary - Culvert 2 Barrel Shape: Pipe Arch Barrel Span: 64.00 in Barrel Rise: 43.00 in Barrel Material: Steel or Aluminum Embedment: 0.00 in Barrel Manning's n: 0.0240 Culvert Type: Straight Inlet Configuration: Mitered Inlet Depression: NONE

Site Data - Culvert 2 Site Data Option: Culvert Invert Data Inlet Station: 0.00 ft Inlet Elevation: 5085.50 ft Outlet Station: 42.00 ft Outlet Elevation: 5085.00 ft Number of Barrels: 3 Table 3 - Culvert Summary Table: Culvert 2

Total Culvert Headwater Inlet Outlet Outlet Tailwater Flow Normal Critical Outlet Tailwater Discharge Discharge Elevation Control Control Velocity Velocity Type Depth (ft) Depth (ft) Depth (ft) Depth (ft) (cfs) (cfs) (ft) Depth (ft) Depth (ft) (ft/s) (ft/s) 850.00 485.74 5093.29 7.792 7.166 7-M2c 3.583 3.028 3.028 2.274 11.686 4.535 1400.00 547.57 5094.66 9.157 8.393 7-M2c 3.583 3.178 3.178 3.086 12.750 5.264 3280.00 662.94 5098.10 12.259 12.604 4-FFf 3.583 3.362 3.583 5.119 15.208 5.965 4495.00 686.73 5099.96 13.024 14.460 4-FFf 3.583 3.386 3.583 6.392 15.754 4.866 5710.00 734.51 5101.61 14.641 16.111 4-FFf 3.583 3.380 3.583 6.809 16.850 5.178 6925.00 777.66 5103.14 16.196 17.642 4-FFf 3.583 3.310 3.583 7.155 17.840 5.487 8140.00 817.14 5104.58 17.695 19.084 4-FFf 3.583 3.583 3.583 7.452 18.746 5.800 9355.00 852.83 5105.95 19.115 20.453 4-FFf 3.583 3.583 3.583 7.739 19.565 6.061 10570.00 885.79 5107.26 20.480 21.763 4-FFf 3.583 3.583 3.583 8.008 20.321 6.298 11785.00 916.71 5108.52 21.807 23.023 4-FFf 3.583 3.583 3.583 8.255 21.030 6.528 13000.00 943.25 5109.74 22.983 24.242 4-FFf 3.583 3.583 3.583 8.578 21.639 6.572 ******************************************************************************** Straight Culvert

Inlet Elevation (invert): 5085.50 ft, Outlet Elevation (invert): 5085.00 ft

Culvert Length: 42.00 ft, Culvert Slope: 0.0119

********************************************************************************

ATTACHMENT C POST PROJECT

HY-8 Culvert Analysis Report Crossing Front View (Roadway Profile): Post-Project

Crossing Discharge Data Discharge Selection Method: Specify Minimum, Design, and Maximum Flow Minimum Flow: 850 cfs Design Flow: 1400 cfs Maximum Flow: 13000 cfs Tailwater Channel Data - Post-Project Tailwater Channel Option: Irregular Channel Channel Slope: 0.0045 User Defined Channel Cross-Section: Coord No. Station (ft) Elevation (ft) Manning's n 1 0.00 5096.40 0.0350 2 13.00 5096.00 0.0350 3 113.69 5094.10 0.0350 4 141.60 5093.75 0.0350 5 168.20 5093.67 0.0350 6 192.70 5093.52 0.0350 7 223.10 5093.33 0.0350 8 253.60 5092.44 0.0350 9 282.50 5091.07 0.0350 10 310.20 5089.65 0.0350 11 349.70 5087.64 0.0350 12 370.00 5085.00 0.0350 13 443.00 5085.00 0.0350 14 445.00 5088.32 0.0350 15 495.80 5090.91 0.0350 16 524.70 5090.96 0.0350 17 551.00 5090.86 0.0350 18 577.20 5090.81 0.0350 19 605.70 5090.18 0.0350 20 632.50 5090.56 0.0350 21 727.10 5092.00 0.0350 22 742.20 5093.00 0.0350 23 747.50 5094.00 0.0350 24 751.60 5095.00 0.0350 25 755.90 5096.00 0.0350 26 760.70 5097.00 0.0350 27 765.70 5098.00 0.0350 28 785.69 5098.50 0.0000

Roadway Data for Crossing: Post-Project Roadway Profile Shape: Constant Roadway Elevation Crest Length: 78.00 ft Crest Elevation: 5090.75 ft Roadway Surface: Paved Roadway Top Width: 28.00 ft

Culvert Data Summary - Culvert 1 Barrel Shape: Pipe Arch Barrel Span: 64.00 in Barrel Rise: 43.00 in Barrel Material: Steel or Aluminum Embedment: 0.00 in Barrel Manning's n: 0.0240 Culvert Type: Straight Inlet Configuration: Mitered Inlet Depression: NONE

Site Data - Culvert 1 Site Data Option: Culvert Invert Data Inlet Station: 0.00 ft Inlet Elevation: 5085.50 ft Outlet Station: 55.00 ft Outlet Elevation: 5085.00 ft Number of Barrels: 6 Table 3 - Culvert Summary Table: Culvert 1

Total Culvert Headwater Inlet Outlet Outlet Tailwater Flow Normal Critical Outlet Tailwater Discharge Discharge Elevation Control Control Velocity Velocity Type Depth (ft) Depth (ft) Depth (ft) Depth (ft) (cfs) (cfs) (ft) Depth (ft) Depth (ft) (ft/s) (ft/s) 850.00 768.54 5091.24 5.741 5.435 7-M2c 3.583 2.698 2.698 2.274 10.126 4.535 1400.00 888.79 5092.42 6.921 6.683 7-M2t 3.583 2.905 3.086 3.086 10.550 5.264 3280.00 1023.80 5095.23 8.351 9.727 4-FFf 3.583 3.097 3.583 5.119 11.743 5.965 4495.00 1040.39 5096.67 8.534 11.167 4-FFf 3.583 3.115 3.583 6.392 11.934 4.866 5710.00 1117.13 5097.89 9.403 12.390 4-FFf 3.583 3.201 3.583 6.809 12.814 5.178 6925.00 1181.14 5098.95 10.168 13.453 4-FFf 3.583 3.261 3.583 7.155 13.548 5.487 8140.00 1400.00 5099.95 13.452 16.503 4-FFf 3.583 3.406 3.583 7.452 16.059 5.800 9355.00 1400.00 5101.03 13.452 16.790 4-FFf 3.583 3.406 3.583 7.739 16.059 6.061 10570.00 1400.00 5102.05 13.452 17.059 4-FFf 3.583 3.406 3.583 8.008 16.059 6.298 11785.00 1415.30 5103.02 13.708 17.516 4-FFf 3.583 3.406 3.583 8.255 16.234 6.528 13000.00 1457.17 5103.92 14.424 18.424 4-FFf 3.583 3.432 3.583 8.578 16.714 6.572 ******************************************************************************** Straight Culvert

Inlet Elevation (invert): 5085.50 ft, Outlet Elevation (invert): 5085.00 ft

Culvert Length: 55.00 ft, Culvert Slope: 0.0091

********************************************************************************

Solicitation Document Report

Report Executed By Peter Brennan Report Executed On 2018/09/19 09.41.52 Solicitation 6888-18 - North County Line Road over Little Thompson River Low Flow Crossing Suppliers Suppliers who have downloaded a document

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David Groy Full 1/1 Richard B Valdez 6888_18.pdf 2018/09/10 12295 W. 48th Avenue 303-980-4101 13 303-980-4101 Wheat Ridge, CO [email protected] [email protected] ROCKY MOUNTAIN SIGNING, PAT TRYON Full 1/1 PAT TRYON 6888_18.pdf 2018/09/18 INC 303-840-9877 303-840-9877 10335 SOUTH PROGRESS WAY [email protected] [email protected] PARKER, CO Rock and Co. Dean MacLennan Full 1/1 Dean MacLennan 6888_18.pdf 2018/09/10 PO Box 568 303-210-1925 303-210-1925 Brighton, CO [email protected] [email protected] Site Work Solutions George DWhitmer Full 1/1 George DWhitmer 6888_18.pdf 2018/09/11 3931 Holly Street (303) 988-5148 (303) 988-5148 Denver, CO [email protected] [email protected] 2018/09/17 Structures, Inc. Tom Jackson Full 1/1 Tom Jackson 6888_18.pdf 2018/09/10 4 Inverness Court East Suite #250 303-770-7878 303-770-7878 Englewood, CO [email protected] [email protected] Terra Constructors Inc. 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From: "Rogstad - DNR, Larry" Subject: Re: Programmatic SB40 request for North County Line Road crossing of the Little Thompson River Date: Thu, December 14, 2017 4:33 pm To: [email protected]

Julia, Received the associated email from you concerning SB40 Programmatic Certification for work on bridge/crossing of Little Thompson river in vicinity of 4200 North County Line Road, Longmont Colorado 80513. On review Colorado Parks and Wildlife concurs that programmatic certification on this project is warranted and no further review or comment is needed. Please keep a copy of this email on file as record of decision on this matter. Thanks, Larry Rogstad, Area Wildlife Manager.

On Mon, Dec 11, 2017 at 3:11 PM, Julia Auckland wrote: Larry,

I am writing to request Programmatic SB40 Wildlife Certification for stream crossing repair work planned by Boulder County Transportation for Spring 2018. The crossing was damaged by flooding in 2013 and 2015. The repairs are being reimbursed by the Federal Emergency Management Agency (FEMA). FEMA requires NEPA compliance and SB 40 Certification. I discussed this project with you on July 28, 2017. Here is the project information you requested:

Location: The project is at North County Line (NCL) Road over the Little Thompson River on the border of Boulder and Larimer Counties, approximately five miles north of the City of Longmont (Longmont). The approximate street address is 4200 North County Line Road, Longmont, Colorado 80513.

Length and Area of Impacts: The total project area is approximately 0.76 acre. The project length along NCL Road is 265 feet. At the crossing, impacts will extend 40-50 feet upstream and downstream. The project would permanently impact 0.036 acre of Waters of the US (WUS) (0.019 acre of wetland and 0.017 acre of open water) due to installation of riprap and concrete to protect the crossing. Temporary impacts to WUS would be 0.060 acre (0.036 acre of wetland and 0.025 acre of open water) due to construction access (acreages do not add up exactly due to rounding). Since impacts do not exceed 0.10 acre, mitigation is not expected to be required by the US Army Corps of Engineers (USACE). Although no direct mitigation is anticipated, the project will help restore the area to pre-2013 flood conditions by re-seeding with native species, adding willow cuttings, and planting cottonwood trees.

Why I think Programmatic: 1. The project does not meet any of the criteria that would require formal certification per SB40 Section IV. A. 2. Impacts would be minor because work is limited to areas that have been repeatedly disturbed by flooding and subsequent repair work in 2013 and 2015. All the wetlands that would be impacted consist of early successional species that have become established since the most recent repair work in Fall 2015. Most of the wetlands are unstable and associated with shifting sandbars in the channel. 3. The project is of short duration; construction is expected to be completed in less than two months. The majority of the in-stream work is expected to be completed within two weeks. 4. The project is not expected to impact any protected fish or sport fish. Per the December 2014 "Little Thompson River Master Plan," recent CPW fish collection found only common species. Furthermore, aquatic habitat in the project area is of low quality because water is only a few inches deep most of the year and there is no established riparian vegetation. The project meets the requirements of FEMA's 2015 Programmatic Agreement with the USFWS and will follow the required conservation measures in order to avoid impacts to federally-listed species.

Plans: On the phone, you said no plans are needed for a Programmatic Clearance. However, in case you need any additional details I have attached; 1. The USACE Pre-construction notification; this includes a project location and description, evaluation of impacts to federally-listed species, relevant plan sheets, and site photos. 2. Plan Sheet 5 because it includes the environmental notes, such as measures to control aquatic nuisance species.

Please contact me if you have any questions or need additional information. Thanks for your help with this project.

Julia Auckland

______

303-358-2687

[email protected]

Auckland Environmental Consulting

Wetlands - Wildlife - Vegetation

--

Larry Rogstad Area Wildlife Manager Area 2

P 970.472.4461 | F 970.472.4468 | C 970.302.7394 4207 W CR 16E, Loveland, CO 80537 [email protected] | cpw.state.co.us

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