Project No. S8875-06-88
June 28, 2006
Mr. Steve Werner
Caltrans District 1
Environmental Engineering Office
1656 Union Street
Eureka, California 95501
Subject: US-101 LAYTONVILLE CURVE CORRECTION PROJECT
LAYTONVILLE, MENDOCINO COUNTY, CALIFORNIA
CONTRACT NO. 03A0937, TASK ORDER NO. 88, EA 01-429300
SUMMARY OF POTHOLING SERVICES AND
SUPPLEMENTAL SITE INVESTIGATION REPORT
Dear Mr. Werner:
In accordance with California Department of Transportation (Caltrans) Contract No. 03A0937 and Task Order (TO) No. 88, Geocon Consultants, Inc. is submitting this Summary of Potholing Services and Supplemental Site Investigation Report for the subject project. This Report summarizes the scope of services performed including 14 exploratory potholes, four hand-auger borings, and laboratory testing to assess heavy metal concentrations in soil at the Site.
PROJECT LOCATION AND DESCRIPTION
The Site consists of roadway, shoulders and sidewalks within 3 meters (m) (10 feet [ft]) of and within Caltrans right-of-way along US Highway 101 (US-101) from Kilometer Post (KP) 110.88 to 111.68 (Post Mile [PM] 69.3 to 69.8) near the intersection of US-101 and Branscomb Road in Laytonville, Mendocino County, California. Site location and approximate project limits are depicted on the Vicinity Map, Figure 1. Site boundaries are depicted on the Site Plan, Figure 2. Caltrans intends to lower the vertical curve on US-101 and improve shoulders and sidewalks.
PURPOSE
Previous investigations at the Site have determined shallow soil is impacted with petroleum hydrocarbons, but previous investigations have not evaluated shallow soil for metals content. Caltrans also needed to locate an Asbestos Concrete Pipe (ACP) waterline within the project limits to determine if its presence conflicted with proposed highway improvements. Additionally, it was suspected that undocumented underground storage tanks (USTs) were present at certain locations within the project limits.
TO No. 88 was written to provide potholing services. Additional exploratory potholing, soil sampling, and laboratory analysis was also included in the TO scope. The primary purpose of the scope of services outlined in TO No. 88 was to (1) provide potholing services to locate the ACP waterline; (2) provide exploratory potholing to attempt to locate suspected fuel USTs; and (3) evaluate metals content of near-surface soils from areas with the highest reported levels of petroleum hydrocarbon impacts for subsequent disposal characterization purposes.
BACKGROUND
The Site lies in the vicinity of several businesses that were former service stations, including Aragon’s Muffler Shop and the Stewart Building, located northeast of the intersection of US-101 and Branscomb Road. Five USTs were reportedly removed from the Aragon property in 2002. Caltrans reported that no records were available regarding the presence of USTs on the Stewart property.
A site investigation conducted after the Aragon tanks were removed indicated total petroleum hydrocarbons as gasoline and diesel (TPHg and TPHd) contamination was present in soil and groundwater deeper than 2.13 m (7 ft) below ground surface (bgs) within Caltrans right-of-way. Caltrans personnel also reported petroleum hydrocarbon odors in excavated soil during previous site investigations and while potholing the Site to determine the depth of utilities near the drainage culvert under US-101 near Geiger’s Market.
At a Caltrans public meeting in early 2005, two Laytonville residents indicated that USTs were present “in the middle of Highway 101” servicing one of the businesses adjacent to the Site. Since USTs were removed from the Caltrans right-of-way when the “Aragon’s Muffler” tanks were pulled, it was not known if the tanks referred to by the residents were among them, or if they were still present.
In June 2005, Geocon performed a preliminary site investigation (PSI), including six direct-push borings (TO47-1 through TO47-6), two hand-auger borings (TO47-7 and TO47-8), soil sampling and analysis, and a geophysical survey. The six direct-push borings ranged in depth from approximately 0.61 to 1.22 m (2.0 to 4.0 ft) and the two hand-auger borings ranged in depth from 0.43 to 0.61 m (1.4 to 2.0 ft). The findings of the PSI indicated diesel contamination in each of the soil samples. The samples were reported to contain TPHd at concentrations ranging from 180 to 840 milligrams per kilogram (mg/kg) and oil and grease at concentrations ranging from 2,200 to 5,500 mg/kg. Because samples were collected as depth composite samples, Geocon was unable to determine whether contamination was present throughout the soil profile or restricted to a particular stratum. The geophysical survey did not detect USTs within the area surveyed.
In October/November 2005, Geocon performed a Site Investigation (SI) to provide additional information on the extent of TPHd and motor oil (TPHmo) contamination within proposed areas of excavation on the Site and to determine reuse or disposal options for impacted soils. The SI included two hand-auger borings and 18 direct-push borings (LV1 through LV20), and collecting 60 soil samples for analysis. Hand-auger borings were excavated to an approximate depth of 0.71 m (2.3 ft) bgs. Direct-push borings were advanced to depths ranging from 0.36 to 1.22 m (1.2 to 4.0 ft) bgs. Soil samples were obtained from various depths. TPHd was reported in each of the samples at concentrations ranging from 1.7 to 4,300 mg/kg. TPHmo was reported above the method reporting limit of 10 mg/kg in 56 of the soil samples collected at concentrations ranging from 14 to 13,000 mg/kg. The laboratory noted that the hydrocarbons reported as diesel did not exhibit a typical diesel chromatographic pattern and that the hydrocarbons had a higher boiling point than typical diesel. Boring locations, geophysical survey area information, and soil analytical test results from the June 2005 and October/November 2005 SI are presented in Appendix A.
We concluded there is vertical stratification of diesel and motor oil contamination at the Site. Reported contaminant levels were generally highest in samples collected from aggregate base (AB) material underlying asphalt concrete (AC) to an average approximate depth of 0.36 m (1.2 ft) bgs, ranging from 42 to 4,300 mg/kg TPHd and 34 to 13,000 mg/kg TPHmo. Reported concentrations for TPHd and TPHmo typically dropped by one to two orders of magnitude in the underlying silt alluvium at approximately 0.51 m (1.7 ft) bgs. The reported TPHd and TPHmo concentrations were at levels that excavated impacted soils would likely require disposal to a Class II landfill as a designated waste. Thus, additional information regarding potential metals content is necessary for further disposal evaluation.
SCOPE OF SERVICES
Outlined below is a summary of the scope of services performed by Geocon under TO No. 88.
Pre-field Activities
· Prepared a Health and Safety Plan (HSP) providing guidelines on the use of personal protective equipment and the health and safety procedures to be implemented during the field activities.
· Notified Underground Service Alert (Ref. Nos. 131749 and 131758) to attempt to delineate subsurface public utilities and conduits in proximity to the excavation locations prior to the field activities. Caltrans personnel marked exploration locations in the field.
· Retained the services of Gregg Drilling & Testing, Inc., a Caltrans-approved and California
C57-licensed contractor, to perform vacuum excavation utility potholing services.
· Retained the services of Sparger Technology, Inc. (Sparger, ELAP No. 1614), a Caltrans-approved and California-certified analytical laboratory located in Sacramento, to perform chemical analysis of soil samples.
Field Activities
Field activities were performed under the direction of Caltrans’ Quality Assurance Manager, Mr. Steve Werner.
· Performed eleven potholes (PH1 through PH11) to locate the existing ACP within the project alignment. Prior to backfilling, potholes were surveyed by Caltrans personnel. Approximate pothole locations are shown on the Site Plan, Figure 2.
· Performed three exploratory potholes (EP1 through EP3) near suspected UST locations. Approximate pothole locations are shown on the Site Plan, Figure 2.
· Performed four hand-auger borings (HB1 through HB4) at selected locations. Approximate boring locations are shown on the Site Plan, Figure 2.
· Obtained twelve soil samples at approximate one-foot intervals directly from the hand-auger borings. Samples were taken directly from the hand-auger bucket and transferred to re-sealable plastic bags, labeled and placed in an ice chest pending delivery to Sparger under chain-of-custody (COC) protocol. Sampling equipment was cleansed prior to collecting each soil sample by washing with an Alconox® solution followed by a double rinse with deionized water. After sample collection, hand-auger borings were backfilled to the surface with excess soil cuttings, paved areas were patched with cold-patch AC or rapid-set concrete.
· Potholing/hand-auger activities generated one drum (55-gallon) of excess soil. We obtained a composite sample from the drum (HB-COMP-DRUM) for disposal characterization. The drum was subsequently transported to Caltrans’ Ukiah Maintenance Station for temporary storage pending disposal.
Laboratory Analysis
Thirteen soil samples (twelve from the hand-auger borings and one from the excess soil drum) were submitted to Sparger for analytical testing.
· Thirteen samples were analyzed for CAM-5 metals: cadmium, chromium, nickel, lead and zinc by Environmental Protection Agency (EPA) Test Method 6010B.
· Two samples (HB-2-2 and HB-3-2) were reanalyzed for total lead by EPA Test Method 6010B, Waste Extraction Test (WET) soluble lead by EPA Test Method 7420, and Toxicity Characteristic Leaching Procedure (TCLP) soluble lead by EPA Test Method 6010B.
· Seven soil samples were analyzed for TCLP soluble chromium by EPA Test Method 7420.
· One sample (HB-3-1) was analyzed for TPHg, TPHd, TPHmo by EPA Test Method 8015B Modified, benzene, toluene, ethylbenzene and total xylenes (BTEX) by EPA Test Method 8021B, and WET soluble chromium by EPA Test Method 7420.
Laboratory Quality Assurance/Quality Control (QA/QC) Procedures
QA/QC procedures were performed for each method of analysis with specificity for each analyte listed in the test method's QA/QC. QA/QC measures included the following:
· One method blank for every ten samples, batch of samples or type of matrix, whichever is more frequent.
· One sample analyzed in duplicate for every ten samples, batch of samples or type of matrix, whichever is more frequent.
· One spiked sample for every ten samples, batch of samples or type of matrix, whichever is more frequent, with the spike made at ten times the detection limit or at the analyte level.
FIELD OBSERVATIONS
Utility pothole locations (PH1 through PH11) were observed, measured, and surveyed by Caltrans personnel. Details of these potholes are not provided in this report.
Exploratory Potholes EP1 through EP3 were performed in areas of suspected USTs. Pothole EP1, performed near the exit driveway of Boomer’s, did not reveal evidence of a UST. Pothole EP2, performed near the former fuel dispenser island near Aragon’s Muffler Shop encountered former product lines but did not encounter a UST. Further probing in this area indicated UST(s) may be present in front of the adjacent tattoo/salon shop. Pothole EP3 was performed in the area where an exploratory drill rig lost a portion of an auger in a suspected UST or void. The auger and void were observed, but no UST. It is possible that the UST, if present, has collapsed. Photoionization detector (PID) readings within the pothole ranged from 120 to 240 parts per million (ppm), indicating the presence of petroleum hydrocarbons.
SOIL ANALYTICAL RESULTS
Soil analytical results are summarized on Tables 1 and 2. Laboratory reports and chain of custody documentation are presented in Appendix B.
Cadmium was not detected above the laboratory method detection limit of 0.50 mg/kg for each soil sample. Chromium, nickel, and zinc were detected at assumed naturally occurring background levels in each soil sample. Lead was detected in each soil sample at concentrations ranging from 5.0 to 1,060 mg/kg. The highest lead concentrations were detected in samples HB-2-2 and HB-3-2 at concentrations of 583 and 1,060 mg/kg, respectively. These two samples were re-homogenized and analyzed for total lead which resulted in concentrations of 348 and 52.6 mg/kg, respectively. WET soluble lead concentrations for these samples were 14.6 and 2.05 milligrams per liter (mg/l), respectively. TCLP soluble lead concentrations for these samples were 0.604 and 0.0764 mg/l, respectively. WET soluble chromium was detected at a concentration of 0.182 mg/l in sample HB-COMP-DRUM. TCLP soluble chromium was not detected above the laboratory method detection limit of 0.050 mg/l for each of the seven soil samples analyzed.
TPHg, TPHd, and BTEX were not detected above their respective laboratory method detection limits in sample HB-3-1. TPHmo was detected at 440 mg/kg in sample HB-3-1.
CONCLUSIONS AND RECOMMENDATIONS
Based on the results of this supplemental site investigation, elevated lead levels exceeding California hazardous waste criteria was encountered at sample locations HB2 and HB3 at a depth of 0.61 m (2 ft). After analysis, the analytical laboratory returned the impacted samples to our office. Based on our observations, the samples contained fragments of glass. No other debris, such as paint chips or metal, was observed in the samples. The remaining metals were reported at concentrations within the range of naturally occurring background levels.
Excess excavated soil generated within the projects limits should be stockpiled and resampled to confirm waste classification in accordance with specific disposal facility acceptance criteria. In addition to petroleum hydrocarbons, the stockpile characterization samples should be analyzed for lead content.
Based on the analytical data generated to date, the majority of the excavated soil materials should be suitable for disposal to an accepting Class II disposal facility. Excavated soil materials that contain lead above 350 mg/kg (Section 25157.8 of the California Health and Safety Code) or at levels that exceed California hazardous waste criteria will require disposal to an accepting Class I disposal facility.
Per the requirements of CCR Title 8, Section 1532.1, the “Lead in Construction” standard, the contractor(s) should prepare a project-specific Lead Compliance Plan (LCP) and HSP to prevent or minimize worker exposure to lead and petroleum hydrocarbon contaminated soil. The plan(s) should include protocols for environmental and personnel monitoring, requirements for personal protective equipment, dust control, and other health and safety protocols and procedures for the handling of contaminated soil.
LIMITATIONS
This report has been prepared exclusively for Caltrans. The information contained herein is only valid as of the date of the report and will require an update to reflect additional information obtained.
This report is not a comprehensive site characterization and should not be construed as such. The findings as presented in this report are predicated on the results of the limited sampling and laboratory testing performed. In addition, the information obtained is not intended to address potential impacts related to sources other than those specified herein. Therefore, the report should be deemed conclusive with respect to only the information obtained. We make no warranty, express or implied, with respect to the content of this report or any subsequent reports, correspondence or consultation. Geocon strived to perform the services summarized herein in accordance with the local standard of care in the geographic region at the time the services were rendered.