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Home My WebLink AboutMethane Gas Venting in Residential Neighborhoods - Site Over (3) 04/27/98 - Council/Agency Agenda - Page 3 7. (City Council) Methane Gas Venting In Residential Neighborhoods - Site Overview. •'(15 Minutes) ` Staff report from the Fire Chief regarding Methane Gas Venting and a Site Overview. Staff Presentations - Duane Olson, Division Chief/Fire Marshal Public Participation - Questions and'Answers 8. (City Council) Economic Development Update - Huntington Beach Economic Development Status Report Which Covers Various City Locations Including Waterfront Project And Neighborhood Shopping Centers (15 Minutes) Communication from the Economic Development Director transmitting the Economic Development Status Report which covers various locations in the city. This meeting's presentation will focus on the Waterfront project and neighborhood shopping centers that serve the area. Staff Presentations - David Biggs, Economic Development Director Public Participation - Questions and Answers Public Comments (30 Minutes) COUNCIL/AGENCY ADJOURNMENT: To Monday, May 4, 1998, at 5:00 p.m., in Room B-8, Civic Center, 2000 Main Street, Huntington Beach, California 92648. i CONNIE BROCKWAY, CITY CLERK City of Huntington Beach, 2000 Main Street- Second Floor Huntington Beach,California 92648 Telephone: 714/536-5227 Internet: http://www.ei.huntington-beach.ca.us (3) METHANE GAS VENTING (SITE OVERVIEW) Prior to the 1940's, the Christine/Susan area consisted of a coastal marsh area, similar to the marsh that currently exists north of Pacific Coast Highway. During the 1940's, runoff from agricultural development in the area was channelized into earthen channels of the current Huntington Beach and Talbert channels. The residential tract was developed in the early 1960's. Pad grading for the tract consisted of placing imported fill over the former marsh and developing the pad and street grades slightly higher than existed within the coastal marsh. Shortly after completion of the development, hydrogen sulfide odors were noted within the area. Problems with ground gas accumulation continued in the area for decades. In 1989, the State of California granted the City of Huntington Beach funding to evaluate and remediate the methane and hydrogen sulfide gas hazard in the area. As a result of a competitive bidding process by the City, GeoScience Analytical, Inc. (GSA) of Simi Valley, California was retained by the City to perform an investigation of the extent of the ground gas conditions, and to recommend and implement mitigation measures. In 1991, GSA identified areas of very high concentrations of methane and hydrogen sulfide gas on Christine Drive between Susan and Islander Lanes with the use of shallow soil gas probes to a depth of 4 feet and small diameter borings to a maximum depth of 18 feet. GSA were unable to identify the source of methane and hydrogen sulfide. However, in 1997, leakage from domestic sewer lines may be contributed factor. Passive venting systems were installed to a depth of 6 feet below the ground surface along the south side of Christine Drive to vent the methane and hydrogen sulfide gas collecting in the subsurface. The City of Huntington Beach also implemented measures to seal leaks in the domestic sewer lines through slip line installations to eliminate the suspected source of hydrogen sulfide odors. In 1993, GSA performed another round of sampling in the area, to investigate continued complaints of odors and dying landscaping in the area of the Christine Drive gas plume. Following this investigation, GSA concluded that the gas plume had expanded to the west, and had identified several other areas that had high levels of methane and hydrogen sulfide gas in the subsurface on Islander Lane and Susan Lane. GSA recommended that an additional trench be installed on the north side of Christine Drive, adjacent to the existing vent system, and another small trench be installed near the intersection of Islander Lane and Christine Drive. The smaller trench on Islander Lane was installed in 1993, the trench to the north of Christine Drive was installed in May 1994. In March through August 1994, the Orange County Flood Control District (OCFCD) installed sheet piling along the earthen levees as part of improvements to the Huntington Beach and Talbert channels. It is reported that several months after installation of the sheet piling, there was an increase in complaints from homeowners in the area regarding foul odors and dying landscaping noted in the area of the high ground gas concentrations. As a result of the renewed complaints, the City of Huntington Beach engaged GSA to conduct another round of sampling in May 1995. At this time, GSA detected a peak concentration in the Christine Drive area. Based on this data and GSA's reported observations of seepage within gas collection trench excavations, GSA concluded that the sheet piling installed within the Huntington Beach and Talbert channel right-of-way may have caused a rise in groundwater level in the area, thereby decreasing the effectiveness of the previously installed gas collection system. yZ7-fBj:,Qy • Gw.,,�.�,C �1'1eef.•�� , In November 1995, Ben Yang & Associates (BYA) was authorized by OCFCD to conduct an independent hydrogeologic study of the area with special emphasis on the effect of sheet pile installation to the gas venting system as described. Based upon OCFCD research, they concluded that the installation of sheet piles along the Huntington Beach and Talbert channels has not significantly altered groundwater elevations and not adversely impacted the ground gas venting system. Passive ground gas collection trenches were constructed as part of GSA's work in the area in 1991, 1993, and 1994, with additional ground gas collections by GSA in June 1995 and February 1997. Each of these trenches consists of an unlined trench excavated to a maximum depth of approximately 6 feet. The lower 3 feet of the trenches was filled with 3/-inch gravel. A slotted PVC collection pipe was installed above the gravel at a depth of about 2 to 3 feet below the ground surface and the trench was then capped with a layer of bentonite. The system was vented through a "dummy" light post to the atmosphere. Venting trenches are located on the north and south sides of Christine Drive between Susan and Surfrider Lanes and on the eastern side of Islander Lane, adjacent to Christine Drive. In 1997, GSA personnel performed a soil probe analyses on Susan Drive. Soil gas, collected from depths of 4 feet below grade at 20 locations (shown on Figure 5) were analyzed for total combustible gas and hydrogen sulfide concentrations. A gas anomaly has been identified within the public right-of-way similar to that previously identified. Concentrations at more depth ranged from 5.0% to >100% of the L.E.L. During the field investigation, selected property owners were interviewed. No homeowner identified recent noxious odors within a dwelling. Previously identified odors within structures were discussed with reference to "gaseous bubbling" out of toilet bowls. Hydrogen sulfide concentrations within the soil probe samples were below the detection limit except for 2 locations in which concentrations of 1.0ppm and 3.Oppm were identified. These elevated concentrations were within the combustible gas anomaly discussed. Based on all available data, it appears that the surfical soil gas anomaly is within the public right- of-way and may be resulting from the seepage of methane and hydrogen sulfide from within the sewer main as suggested in previous investigations. sImAolsoMmethane(04/23/98) O.C.F.C.D. 1 rn 4U O s o a. w r 3 u. CO ..r• r..r ^' � V � W U3(3Nb'"ISI m J O cc H wCC IL W u. 6� co byb�s � V � a uJ J Z d-InH ,• V Q — —> Z CD z � za V • W FIGURE 2 3s 4U 41 42 4 J 4 _ C 336�V 2 38 816 3„ O1 1 10 5 3 l'J 27' vQ- GROUND GAS PROBES (not to scale) SHEETJOB GEOSCIENCE TITLE: SOIL PROBE LOCATIONS NO. 1509 ANALYTICAL, PROJECT: Lip INC. COMBUSTIBLE GAS . FER Simi Valley,Cl street EVALUATION Simi Valley,CA 93063 TEL (805)526-6532 FAX 526-3570 DWG. 2 NO: reHUNTIMMArw FIGURE 3 it Q� `I METHANE/HYDROGEN SULFIDE (not to scale) GEOSCIENGE 8HEETMETHANE OONCENTRATION ISOPLETHS o 1500 ANALYTICAL, PROJECT: Lip INC. COMBUSTIBLE GAS ° . FER BY 44UIndustrial Street Simi 93063 EVALUATION Simi Val{ey,CA TEL (805)526-6532 FAX 626-WO DWG. 3 NO: .HUNTNa7M.drw FIGURE 4 Remediatiors System = J� .0 co Q� Q. Remediation S stem (not to scale) GEOSCIENCE S"ETM ETaEMEDIATION SYSTEM SCHEMATIC 1509 ANALYTICAL, PROJECT. up INC. COMBUSTIBLE GAS . FER ShWV4464 d ' ,CAWWW ` EVALUATION Simf Vaile�l,CA 93063 TEL (805)626. = FAX 52&%WO DWG. F4NO: raHUN Nc37M.a,w FIGURE 5 1 20 22001 22002 12 17 19 11 2 18 13 15 22021 22022 3 10 4 14 9 5 16 22031 8 22032 6 7 217 I+-40.0 ft--►I GEOSCIENCE SHEET SOIL PROBE INVESTIGATION JOB 1867 ANALYTICAL, PROJECT: LJp GHKD INC. SUSAN LANE By,. FER IStreet ndustrial A 93063 CITY OF HUNTINGTON BEACH TEL (805)626-6532 FAX 626-WO 1 NO: FIGURE s 22001 22002 METH ANE p u: 22021 22022 w z 22031 Z 22032 D N 4-4 0.0 ft-M GEOSCIENCE SHEET TOTAL COMBUSTIBLE GAS JOB 1867 TITLE: NO. ANALYTICAL, PROJECT: UP CHKD INC. SUSAN LANE FER 4454 valley Asa CITY OF HUNTINGTON BEACH TEL (805)52&6532 FAX: 52&3570 2 NO: