B08_Attach_6_PGLSR_Rehabilitation_report.pdf

ENGINEER’S REPORT

Structural Observation & Assessment Punta Gorda Lightstation

King Range National Conservation Area Humboldt County, California

For:

Bureau of Land Management U.S. Department of Interior

Arcata Field Office 1695 Heindon Road

Arcata, California 95521

By:

Bruce S. Elster, PE

Shoreline Engineering, Inc.

505 Harbor Street

Morro Bay, CA 93442 email: be@shoreline-engineering.net

8 September 2020

Job #404-07

Ref: Structural Condition Observation Punta Gorda Lightstation

Executive Summary

This report confirms that the Engineer has visited the Punta Gorda Lightstation at the request of the Arcata Field Office, Bureau of Land Management. The Lightstation consists of two structures: the Lighthouse and the Oil House. The Engineer performed a visual non-destructive observation of the buildings. The structures are in varying states of deterioration.

The Lighthouse is in considerably better condition than the Oil House. The report discusses observations, makes an initial structural condition assessment, and outlines possible approaches to rehabilitation.

It is the Engineer’s belief that both structures warrant consideration for rehabilitation efforts to prevent further deterioration. The structures are also believed to be worthy of consideration for stabilization and rehabilitation. This would also include reconstructing portions of the Oil House. Refer to the Conclusions/Recommendations section of the report.

Introduction

The purpose of the Engineer’s on-site observation was to perform an on-site inspection to develop a baseline understanding of the Lightstation’s current structural condition. Building geometry was verified. Information was gathered sufficient to assist the Bureau of Land Management Arcata Field Office in the decision making process regarding possible futures of the Lightstation. The Engineer performed the visual tactile inspection of the Lighthouse and the Oil House on 5 August 2020. Observations were non-destructive.

For the purpose of describing the orientation of features related to the property in this report, the following rules have been used:

1. The Lightstation is generally oriented in a northwest-southeast orientation along the main axes of the structures. For the purpose of this report, compass orientation is taken to be north-south along the main axes of the structures.

Therefore, the entry door to the Lighthouse is on the south side of the structure.

2. References to “view in the ___ direction”, or “looking ___”, are taken as if one is looking toward the referenced direction.

3. References to “view from the ___”, or “looking from the ___”, are taken as if one is looking away from the referenced direction.

The report has been prepared without the benefit of destructive testing, intrusive inspections, geotechnical investigation, or numerical analysis; and as a result, all the information included in the report is subjective in nature. In the event information is provided that contains the results of additional testing, inspection, or evaluations; any opinions, conclusions, or

Ref: Structural Condition Observation Punta Gorda Lightstation King Range National Conservation Area recommendations contained in the report may be revised to reflect findings related to such additional information.

History

Construction of the structures began in 1910. The Lightstation began operating in 1912. The Lightstation was taken out of service in 1951. The structures are included in the National Register of Historic Places.

Documents Reviewed Documents reviewed:

1. The History and Architecture of the Punta Gorda Light Station, King Range National

Conservation Area, Humboldt County, California. Bureau of Land Management, Arcata Field Office. February 2020

2. National Register of Historic Places Inventory--Nomination Form, Punta Gorda Light- Station. United States Department of the Interior, National Park Service. December 30, 1975.

3. California Historic Building Code, 2019 (CHBC)

4. California Existing Building Code, 2019 (CEBC)

5. Structural drawings of the Lighthouse and the Oil House are believed to exist; but, were unavailable for review.

Observations

The Lightstation is located in the King Range at the base of a 900 foot high slope, and above the high tide zone on a fairly level terrace at elevation 50-60 feet. Photo 1. The Lighthouse is founded on a level pad just below what appears to be a minor ridge feature. The Oil House is located on a sloping site below what appears to be the north flank drainage of the Lighthouse ridge. The flank forms a discreet drainage that is directed downslope toward the Oil House.

Refer to Attachment A for the plan set for geometry of both structures. Representative Photos are included in Attachment B. The following observations are broken into two separate lists, one for each structure. Each set of observations is meant to stand alone for the purpose of separating subsequent discussion and evaluation of each structure apart from the other. As a result, many observations are duplicated as they may apply to both the Lighthouse and the Oil House structures.

Ref: Structural Condition Observation

Lighthouse observations made during the site visit include:

1. The Lighthouse is 27 feet in height, and is located on a level pad. Photos 2, 3, 4.

2. The structure consists of reinforced concrete.

3. The walls appear to have plaster applied as a finish coat.

4. The concrete floor appeared to be in fair condition. Photo 21.

5. Cracking observed in the walls was minor. Photo 21. Concrete was sounded with a steel handled rock hammer. Acoustic impact hammer testing was performed to detect delamination or disbonding of concrete.

a. Main portions of the concrete walls appeared to be sound.

b. Areas around window and door openings sounded hollow, indicating delamination, disbanding, or spalling. Photographs showing mold growing around the openings could be indicative of delamination extent. Photos 19, 20, 22.

6. In-situ concrete strength was measured with a Schmidt Hammer. Readings were taken in the field areas where rock hammer soundings indicated solid concrete. Readings were consistent in the range of 3,600 psi to 4000 psi.

7. Concrete spalling was limited mainly to the area around the top of the tower near the turret. Photo 23, 24

8. Observed reinforcing, exposed as a result of corrosion, was of smooth round bar rather than twisted or deformed reinforcing.

9. The center of the structure consists of a circular concrete tower room supporting an iron turret and lantern.

a. A 9-1/2 inch diameter iron column is in the center of the room. Photos 26 & 27.

b. A steel spiral stair is installed on the west side of the room, leading up to the lantern.

It was reported the staircase was not original and of fairly recent construction.

10. The base of the iron column was corroded. An opening in the iron column appeared to be of original construction, heavily corroded. A concrete plug filled the void. The purpose of the plug was not understood.

11. The turret and lantern are of iron construction. Photos 5, 6, 7, 8, 9, 16,17,18

12. The turret exhibited the following:

a. The turret is believed to be of cast iron construction. Cast iron exhibits a higher degree of corrosion resistance than steel.

b. The top surface of the turret deck appeared to be in reasonable condition. Photo 9, 13, 14.

c. The exterior underside of the turret deck exhibited minor to moderate levels of corrosion. Photos 16, 17, 18

d. The interior underside of the turret deck exhibited minor to moderate levels of corrosion. Photo 15, 25.

e. Connections were moderate to severely corroded. Photo 18.

Ref: Structural Condition Observation

13. The lantern is of “conical ring” form. Photos 5, 6, 7.

a. The cast iron muntins layout out to form a 45 degree grid all around.

b. Drilled attachment holes for the attachment of panes are still evident.

c. The lantern framework required panes of similar conical ring form.

14. The Lighthouse roof is formed to provide positive drainage all around. There are two channels, plastered over that run down the length of the structure (N-S). The plaster has collapsed in several locations revealing these channels. Photos 10 ,11 ,12 The purpose of the channels is not known.

Oil House observations made during the site visit include:

15. The Oil House is located on a sloping site. Photo 28, 29, 30. The structure, being positioned on slope rather than a cut pad as with the Lighthouse, is more prone to issues related to settlement. Upslope drainage is directed toward the Oil House via the depression formed between the north flank of the Lighthouse upslope ridge and a more prominent minor ridge just to the north of the Oil House. It is likely that higher levels of soil moisture may be present periodically, lowering the strength of supporting soil.

16. The northwest corner of the building has settled, causing distortion leading to structural damage in the structure. Photo 33, 34, 35, 36, 37, 38.

17. Foundation settlement appears to be differential. The settlement of the northwest corner appears to have led to the following sequence of damage: Photos 31, 32.

a. The northwest building corner, as a result of settlement, has translated out and away from the structure corner in a counterclockwise manner.

b. Clockwise rotation of the wall at its base resulted.

c. The downforce created by the settlement caused a large crack to form in the roof area between the tank room and the south room. The crack appears to have formed a hinge adjacent to the wall separating the two rooms.

18. The portion of the northwest corner of the building exhibiting extensive damage should be considered for reconstruction.

19. The walls appear to have plaster applied as a finish coat. Photo 38.

20. The structure consists of reinforced concrete.

21. Concrete was sounded with a steel handled rock hammer. Soundings were taken where concrete surfaces appeared to be in reasonable fair condition. Acoustic impact hammer testing was performed to detect delamination or disbonding of concrete.

a. Main portions of the concrete walls appeared to be sound. This observation is not to be confused with those portions of wall that are exhibit severe deterioration and distress related to corrosion and settlement.

Ref: Structural Condition Observation

b. Areas around window and door openings sounded hollow, indicating delamination or spalling. Two possibilities seem likely: It seems likely that the concrete surface was plastered at the time of construction, or rust jacking of jamb steel has occurred.

22. In-situ concrete strength was measured with a Schmidt Hammer. As indicated above, readings were taken at locations appearing to be of sound material. Readings were taken in the field areas where rock hammer soundings indicated solid concrete.

Readings were consistent in the range of 3,600 psi to 4000 psi.

23. The roof is formed with a distinct “hip” drainage pattern. The fold lines are distinctly formed in neat straight lines. Photo 39.

24. The open crack in the roof has allowed water to intrude into the concrete and room below. Photos 40, 41, 42

25. Reinforcing steel consists of round bar rather than twisted or deformed bars used in more modern structures.

26. The roof eaves exhibit extensive spalling of concrete. Photos 28, 29, 32.

27. Significant portions of the Oil House structure exhibit damage in the form of cracking, spalling, and rust jacking. Observations indicate areas with highest level of damage occur where distortions related to settlement are evident.

a. The highest level of damage occurs around the northwest window opening and the ceiling at the south end of the tank room.

b. The ceiling in the south end of the tank room is in a severe state. The crack in the roof above allowed water to penetrate into the concrete, accelerating corrosion, rust jacking, and resultant spalling of concrete. This area should be considered for reconstruction.

Comments

Based on observations made during the site visit, the engineer has the following comments:

1. Both structures exhibit varying degrees of deterioration.

2. The walls of both structures exhibited a distinct pattern of response when sounded with the rock hammer.

a. Soundings in the field areas of the walls exhibited a solid ring. A solid acoustic ring indicates sound structure.

b. Soundings adjacent to window and door openings exhibited a dull thud. The dull thud indicates delamination of plaster, or rust jacking of jamb steel.

c. It was not determined which condition would result in a dull thud sounding.

d. The wall surfaces appear to have a uniform finish indicating a plaster coat throughout. Based on the finding that the walls sounded away from openings, the Engineer is led to believe that a delaminated plaster coat is present around the openings. Intrusive examination is necessary to verify whether or not this belief is valid.

Ref: Structural Condition Observation Punta Gorda Lightstation King Range National Conservation Area

3. In-situ concrete strength was measured with a Schmidt Hammer. Readings were consistent in the range of 3,600 psi to 4000 psi for both buildings.

a. Concrete strength readings indicate concrete materials, on average, are in good condition.

b. These results lead the Engineer to believe observed damage (including spalling, and cracking) is more likely the result of rust jacking and structural distortion caused by foundation settlement.

4. The Engineer, in assessing damage or deterioration, relies on nationally accepted standards for making structural condition assessments. The inspection was surficial, or tactile. Rating of deterioration or damage was made based on the California Building Code (CBC) Chapter 31-F Audit Manual. Although the CBC is presented for the purpose of assessing structures in marine oil terminals, the tables used by the Engineer are widely used nationwide for similar inspection work, are codified into the building code, and are considered to be applicable. Applicable pages from the Audit Manual are attached. Refer to Attachment C.

5. Element ratings. Condition ratings are useful in assisting the decision making process.

In the instant case, note that the inspection was surficial and preliminary in nature. More evaluation is warranted. Based on observations made during the inspection, the Engineer makes the following initial condition rating assessments:

Lighthouse

Floor/Foundation Minor

Walls, in general Moderate

Walls, exclusive of top-of-wall at tower Major

Openings, plaster Moderate

Roof Minor

Turret and Lantern Moderate

Turret and Lantern connections Major Oil House

Oil House Floor/Foundation Severe

Walls Severe

Roof Severe Initial condition rating assessments are subject to review after additional investigation is performed. The Major and Severe ratings do not necessarily mean the condition is not suitable for rehabilitation or repair.

6. In the event additional examination and work are planned, consideration of repairs could include; but, not be limited to:

a. Delaminated plaster in both structures should be removed and replaced to prevent accumulation high levels of moisture within the concrete. Should rust jacking be the problem, then concrete repairs would be appropriate.

b. The turret and lantern iron work should be cleaned to bare metal, treated with corrosion resistant materials, recoated, made watertight. Removal to hot dip

Ref: Structural Condition Observation galvanize (or zinc spray metallizing in place), followed by application of a tough marine quality coating (Among other similar products, Carboline 300M is a very tough product designed for this purpose). Having made these suggestions, there are a number of alternative solutions worthy of consideration.

c. Consideration should be made to reinstall “glass” panels in the lantern to prevent water intrusion into the interior.

d. Concrete damage should be considered for repair. There are accepted methods and means to accomplish repair work. Attachment D illustrates a concept method approved by the American Concrete Institute for work related to spalling and crack repair. There are a number of high quality cementitious grout products available that are designed for this purpose. Where corroded reinforcing requires replacement, there are similar methods for replacement and upgrading.

e. Reconstruction of portions of the Oil House may be more cost effective than restoration. The Engineer comments this approach has the benefit of highlighting the interpretive process and preservation of history. Removal and replacement of the northwest corner, damaged portion of the retaining wall, and a portion of the roof should be considered.

f. Roof surfaces should be cleaned to expose the substrate, repair cracks/openings and; then, apply a waterproof coating.

7. Installation of a cathodic protection system should be considered. Cathodic protection works by inducing an electric current of low voltage into the structure to prevent electrochemical degradation of the reinforcing steel.

8. The foundation of the Oil House is a candidate for foundation stabilization. Several repair approaches are available. Should a geotechnical investigation be performed, appropriate repair options can be determined.

Conclusions/Recommendations

Given the observations and comments above, it is the opinion of the engineer that:

1. There are several approaches to further evaluation of both structures. The question as to the ultimate end of any structural evaluation needs to include a determination of: 1) benign neglect with the structures continuing to decline, 2) rehabilitation/stabilization to slow or halt deterioration, 3) reconstruction to rehabilitate and restore the structures to a level that could significantly extend their lives, or 4). a combination that serves to present the structures in keeping with their status as Historic Structures.

2. The Engineer concludes, in part, that both structures warrant additional examination through physical testing to determine their viability for repair, rehabilitation, or reconstruction. Testing could include, at a minimum:

Geotechnical exploration and soil testing adjacent to the Oil House to determine viability for restoration of the foundation to prevent further settlement

Testing of concrete quality is important and may drive the decision making process.

Ref: Structural Condition Observation Punta Gorda Lightstation King Range National Conservation Area

3. Based on observations made by the Engineer, it is recommended that additional examination be made that will lead to an educated decision as to how best to proceed.

4. The Engineer believes the structures are suitable candidates for restoration, and recommends favorable consideration of the effort to prevent further deterioration of the structures.

The report, conclusions, and recommendations are based on observed conditions made during the site visit. If there are any questions or concerns regarding this report, do not hesitate to contact the Engineer directly.

Respectfully submitted.

Attachment A: Lightstation Plans Attachment B: Representative Photography Attachment C: Condition Assessment Rating Tables Attachment D: ACI Concrete Repair Detail

Attachment A Lightstation Plans

Attachment B Representative Photography

Attachment C Condition Assessment Rating Tables

DRAFT - Marine Oil Terminal Audit Manual

Marine Facilities Division 2-3 May 2004 California State Lands Commission

TABLE 2-1

CONDITION ASSESSMENT RATINGS FOR STEEL ELEMENTS

Condition

Rating Existing Damage

Defects Indicating Higher Damage Grade(s)

Not Inspected

Not inspected, inaccessible or passed by(1)

No Damage

Protective coating intact

Light surface rust

Minor

Less than 50 percent of perimeter or circumference affected by corrosion at any elevation or cross section

Loss of thickness up to 15 percent of nominal at any location

Minor damage not appropriate if:

Changes in straight line configuration or local buckling

Corrosion loss exceeding fabrication tolerances (at any location)

Moderate

Over 50 percent of perimeter or circumference affected by corrosion at any elevation or cross section

Loss of thickness 15 to 30 percent of nominal at any location

Moderate damage not appropriate if:

Changes in straight line configuration or local buckling

Loss of thickness exceeding 30 percent of nominal at any location

Major

Partial loss of flange edges or visible reduction of wall thickness on pipe piles

Loss of nominal thickness 30 to 50 percent at any location

Major damage not appropriate if:

Changes in straight line configuration or local buckling

Perforations or loss of wall thickness exceeding 50 percent of nominal

Severe

Structural bends or buckling, breakage and displacement at supports, loose or lost connections

Loss of wall thickness exceeding 50 percent of nominal at any location

(1) If not inspected because of inaccessibility, note as such.

Marine Facilities Division 2-4 May 2004

Marine Facilities Division 2-5 May 2004

TABLE 2-2

CONDITION ASSESSMENT RATINGS FOR REINFORCED CONCRETE ELEMENTS

Condition Rating

Existing Damage Defects Indicating Higher Damage Grade(s)

Not Inspected Not inspected, inaccessible or passed by(1)

No Damage Good original surface, hard material, sound

Minor

Mechanical abrasion or impact dents up to 1 in.

in depth

General cracks up to 1/16 in. in width

Occasional corrosion stains or small pop-out corrosion spalls

Minor damage not appropriate if:

Structural damage

Corrosion cracks

Chemical deterioration(2)

Moderate

Structural cracks up to 1/16 in. in width

Corrosion cracks up to 1/4 in. in width

Chemical deterioration(2): Random cracks up to 1/16 in. in width; “Soft” concrete and rounding of corners up to 1 in. deep

Moderate damage not appropriate if:

Structural breakage and/or spalls

Exposed reinforcement

Loss of cross section due to chemical deterioration beyond “rounding of corner edges”

Major

Structural cracks 1/16 in. to 1/4 in. in width and partial breakages (structural spalls)

Corrosion cracks wider than 1/4 in. and open spalls (excluding pop-outs)

Multiple cracking and disintegration of surface layer due to chemical deterioration

Major damage not appropriate if:

Loss of cross section exceeding 30 percent due to any cause

Severe

Structural cracks wider than 1/4 in. or complete breakage. Loss of bearing and displacement at connections

Complete loss of concrete cover due to corrosion of reinforcing steel with over 30 percent of diameter loss for any main reinforcing bar

Loss of concrete cover (exposed steel) due to chemical deterioration

Loss of over 30 percent of cross section due to any causes described above

(1) Same as footnote 1 on previous table.

(2) Chemical Deterioration: Sulfate attack, alkali-silica reaction or ettringite distress.

Marine Facilities Division 2-6 May 2004

Attachment D ACI Concrete Repair Exhibit