Flood Analysis of the Kings River at the Vulcan Materials Company Sanger – Centerville Project Prepared for: Vulcan Materials Company Fresno, California July 2004 Technical Memorandum A Flood Analysis of the Kings River at the Sanger – Centerville Project Vulcan Materials Company Contents Project Summary..........................................................................................................................1 Objectives......................................................................................................................................2 Site Description............................................................................................................................2 Kings River....................................................................................................................................2 FEMA Flood Insurance Study ...................................................................................................3 Analysis of the Kings River at the Project Site ......................................................................3 Hydraulic Analysis of the Kings River Channel...................................................................4 Hydraulic Analysis of the Secondary Channels....................................................................5 Results of Hydraulic Analyses..................................................................................................5 Evaluation of Erosion..................................................................................................................6 Recommendations .......................................................................................................................7 Assumptions and Conditions....................................................................................................7 i A W04/22517/001.doc Flood Analysis of the Kings River at the Sanger – Centerville Project Vulcan Materials Company Tables Table 1 Flows in the Kings River ..........................................................................................4 Table 2 Results of HEC-2 Analysis .......................................................................................6 Figures Figure 1 Location Map................................................................................... Follows Page 7 Figure 2 Mining Plan ..................................................................................... Follows Page 7 Figure 3 Reclamation Plan ............................................................................ Follows Page 7 Figure 4 Flood Insurance Rate Map............................................................. Follows Page 7 Figure 5 100-year Flows................................................................................. Follows Page 7 Figure 6 Aerial Photograph .......................................................................... Follows Page 7 Figure 7 Profile of the Kings River............................................................... Follows Page 7 Appendix Cross-Sections ii A W04/22517/001.doc Flood Analysis of the Kings River at the Sanger – Centerville Project Vulcan Materials Company Flood Analysis of the Kings River at the Vulcan Materials Company Sanger – Centerville Project Project Summary Vulcan Materials Company (Vulcan) is proposing to expand its current aggregate (sand and gravel) mining operations located along the State Highway 180 approximately one-half of a mile east of Centerville and includes portions of Sections 8, 9, 17 and 18 of T14S/R23E. The land is generally located between the State Highway 180 on the north, Kings River on the east, and Riverbend Avenue on the west as shown on Figures 1 and 2. Aggregate mining activities have occurred on this site since the 1940’s. The operations were acquired by Vulcan Materials Company in 1999. The project site is 683 acres. Operations are currently permitted on 226 acres of the project site under Fresno County Conditional Use Permits (CUP) 1466 and 1656 granted in 1978 and 1981 respectively. Expansion of aggregate mining is proposed for approximately 457 acres of the project site. Reclamation of the project site will create 683 acres of open space, wetlands, ponds and wildlife habitat. Figure 2 shows the Mining Plan and Figure 3 shows the Reclamation Plan. Mining is currently accomplished using conventional mining methods and equipment to extract sand and gravel. Due to the proximity of the water table to the natural ground surface (5 to 15 feet), dewatering of the active mining area occurs to allow “dry mining”. Mined material is washed and processed at an on-site aggregate plant, and the products are then sold to outside customers or to the on-site ready mixed concrete plant or the asphalt concrete plant. The proposed expansion of the operation onto the adjacent property will convert mining to a “wet mining” method by employing a floating excavator as the primary means to extract material below the water table instead of dry mining. As technology improves or mining conditions change, it is possible that other mining methods could be employed. These methods will not require dewatering. Wash/process water is pumped to a silt pond. After the sediment has settled out the water is decanted to a supply pond next to the Kings River where the dewatering water also is pumped. Water from the supply pond is recycled to the processing plant as wash water. Water from the supply pond also is discharged to the River in accordance with the waste discharge requirements of Central Valley Regional Water Quality Control Board Order No. 5-00-007, adopted January 28, 2000. 1 A W04/22517/001.doc Flood Analysis of the Kings River at the Sanger – Centerville Project Vulcan Materials Company Project plans indicate that several ponds will be formed on the project site. There will be a margin of land between the Kings River supply pond and future ponds. Objectives The Federal Emergency Management Agency (FEMA) Flood insurance maps indicate that waters during the 100-year storm event will leave the Kings River channel and flood the eastern portion of the project site. The objectives of this technical analysis are (1) to determine if the 100-year flow in the Kings River under 2004 conditions will flood the project site as shown on the FEMA maps, and (2) identify flood control measures that will protect the project site if flooding will occur during the 100-year event. Site Description The project site contains approximately 683 acres and is located two miles east of the City of Sanger. The north boundary of the property is along Highway 180. The Kings River flows from north to south, and its channel is located along the eastern boundary of the project site. Collins Creek and China Creek are located west of, and parallel to, the Kings River. These two cheeks flow through the western portion of the project site. East of the Kings River are the East Branch of the Kings River and Cameron Slough. Collins Creek, China Creek and Cameron Slough are tributaries of the Kings River. The project site has a ground slope of approximately 0.0025 to the southwest. The highest elevation on the property is 385 feet at Highway 180. There is approximately 7 feet of topsoil and silty sand overlying the sand and gravel deposits on the project site. Sand and gravel mining is ongoing at the central portion of the project site. The west half of the project site is currently farmed, and the north portion of the property is agricultural land. Current and previous agricultural uses of the property include orchards and pasture. Kings River The Kings River watershed covers portions of Fresno and Tulare Counties. From its headwaters in the Sierra Nevada Mountains, the Kings River flows westerly to Pine Flat Lake, formed by Pine Flat Dam. The watershed upstream of Pine Flat Lake is approximately 1,500 square miles. From Pine Flat Lake, Kings River flows southwest and enters the San Joaquin Valley floor a few miles northeast of the City of Sanger. The River continues southwesterly and empties into Tulare Lake Basin that is located approximately 70 miles downstream of Pine Flat Dam. 2 A W04/22517/001.doc Flood Analysis of the Kings River at the Sanger – Centerville Project Vulcan Materials Company Pine Flat was constructed by the U.S. Army Corps of Engineers in 1954 for flood control and irrigation purposes. During heavy storms runoff fills the Pine Flat Lake flood storage space, then the stored water is later released downstream in accordance with pre-established operating rules. One example of the flood reduction capability of Pine Flat Dam was during January 1997 when there was a severe storm during the period December 26, 1996 through January 3, 1997. During this period Pine Flat Lake had a peak hourly inflow of 87,000 cfs and the outflow was limited to 8,100 cfs. During the dry season from April to October, releases from Pine Flat Lake are regulated to meet the pre-established requirements for wetlands and irrigation use. The project site is located within the Kings River Water District, a member unit of the Kings River Water Association. The Association consists of 28 member units, public and private, that hold the water rights to the Kings River. The dry season flows are low compared to the large winter flows, and pose no flood risk to the project site. FEMA Flood Insurance Study In September 1982 the Federal Emergency Management Agency (FEMA) published the report entitled Flood Insurance Study, Fresno County, California. The hydrologic and hydraulic