San Clemente Dam is a concrete-arch dam which was built in 1921 on river Carmel. It is 106 feet high and about 18 miles from the Pacific Ocean (Business wire 1). It was intended to be a source of water of the then fast growing population of Monterey Peninsula as well as serve the tourism industry.
Currently the dam has more than its 90% capacity filled with sediment and its capability to supply water is no more. In the year 1991 a branch of CDWR-California Department of Water Resources, which deals with the safety of dams and other reservoirs, in conjunction with CAW-California American Water, resolved that the dam did not satisfy seismic stability standards (Chapman 1). This meant that something needed to be done to address the safety issues.
A task force from both the CDWR and the USACE-U.S. Army corps Engineers explored several ways of improving the condition of the dam so that it could conform to the seismic safety standards (Coastal conservancy 12).
In the year 2007, CDWR which is the lead agency of the project under the CEQA certified the projects final EIR-Environmental Impact Report also referred to as Environmental Impact Statement (Coastal conservancy 12). The document was also reviewed and approved by the conservancy. The project proposes the rerouting a portion of river Carmel at least half mile down and transforming the arm of the river which is already filled with sediment into a permanent storage area for sediment. I will use the EIR to review the project.
The EIR establishes the major effects that will arise as a result of the project being implemented. The effects cut across the fields of Air quality, cultural resources, fisheries, geology and soils hydrology and water resources, noise, recreation, traffic and circulation, terrestrial biology, water quality and wetlands. Effects in each field will be reviewed separately.
The EIR shows that most of these effects can be mitigated in such a way that they become almost nonexistent through both construction management measures and changes in the design. For instance effects such as loss of habitat for quality fish, increased turbidity, loss of vegetation and increased transport of sediment are all as a result of erosion. In this regard the mitigative measure to be taken is one aimed at reducing soil erosion by strengthening the valley walls and the river banks (Coastal conservancy 13).
Construction management measures have been incorporated in the EIR and will be taken to minimize erosion as well as minimize the effects that could result in loss of rare species and special habitats. Through construction management measures and design changes more than thirty seven impacts are mitigated.
The EIR identifies 26 environmental effects which are very significant but that cannot be mitigated. Out of the 26 effects 23 can only be mitigated up to a certain point and not beyond. Out of the 26 effects 21 are short term and the remaining 5 are long term. The five long term effects cannot be avoided (Coastal conservancy 13).
One of these long term effects include expected increase of days that suspended sediment concentration surpasses 500 parts per million, which is expected to go beyond the baseline by at most 11 days in a period of 41 years(Coastal conservancy 13).
The second long term effect has to do with the excavation of the rerouting channel which will cause complete loss of riparian habitat and brush land. The third long term effect will arise as a result of lost historic structures with reference to the dam itself which has been in existence for more than 90 years.
This will go hand in hand with the fourth long term effect which will be as a result of the setting changes due to the alteration of the dam surrounding and even to the larger historic district of San Clemente Dam and finally the visual integrity of the same historic district will be lost as a result which will be long term effect.
Hydrology & Water Resources
During the construction it is expected that the excavated sediment from the creek of the dam will leave remnants on the canyon walls and these particles will eventually be washed down and transported downstream by the rains.
However these effects can be mitigated to minimize the extent of erosion by making geomorphically firm channels and revegetating the banks to ensure the river channel is maintained and erosion minimized if not eliminated. During heavy rains the sediments tend to increase as a result of high flow of the river. After the dam is removed little sediment will be trapped upstream and the only time there will be sediments being eroded downstream is when there are heavy rains.
During the same period the sediment concentration will increase downstream. A model used to arrive at estimations showed that each river reach would experience excess sediments in respect to 500 parts per million over a period of 41 years. This is expected to go beyond the baseline by at most 11 days in the same period an effect that cannot be mitigated in any way.
When the project is carried out the document considers that the reservoir will be drained of water for two or three years. This is expected to increase the turbidity and at the same time decrease the amount of dissolved oxygen. In addition the temperature of the water in the reservoir will be bound to go up once its volume is reduced.
However reducing the speed at which water will be drawn down can be used to mitigate the temperature effect (California Department of Water Resources 87). All in all the quality of water will be lowered significantly and there is no way to mitigate that effect.
The EIR acknowledges that dewatering the river channels will lead to temporary loss of aquatic life. Though this will be short lived the effect is significant and quite unavoidable. However some form of mitigation is available where by the fish can be rescued and moved to a new location.
At the same time when construction of the diversion channel starts it is estimated that 1700 feet will be lost and this will have two adverse effects in both short term and long term (California Department of Water Resources 91). In the short term there will be alteration of the aquatic habitat and in the long term there will be reduction of the aquatic habitat. These two effects however are both short term and cannot be avoided.
Construction of cofferdam and the dewatering of plunge pool will be unavoidable; the two activities however are bound to have adverse effects on some special status species such as the CRLFs-California red-legged frogs exposing them to the risk of desiccation and predator attacks.
In this case mitigation is possible by way of relocating the special status species to conducive environments such as frog habitats. This form of mitigation of moving aquatic species and the special status species must be done under the watch of CDFG-California Department of Fish and Game as well as USFWS-U.S. Fish and Wildlife Service. The effect here is only temporary habitat loss which is both unavoidable and short term (California Department of Water Resources 96).
The document further considers the fact that by removing the sediment the spawning grounds of the CRLFs will be interfered with. However mitigation is possible and will involve moving the CRLFs to new habitats. The effect is unavoidable, significant and short term.
In order to pave way for the river by pass, a new river channel will have to be excavated leading to loss of brush land habitat and riparian habitat. These two habitats are home to several special status species such as the CRLFs, the western pond turtle and even the coast range newt.
Other terrestrial species such as Monterey dusky footed wood rat may also be affected. Mitigation is also possible in this case where moving the CRLF hatchlings and the turtle pond juveniles to a new habitat will be required. A prior pre construction survey is recommended so as to establish such habitats and avoid them. The impact is significant, long term and unavoidable.
The EIR also considers air pollution in respect to the fact that the project will involve a lot of gaseous emissions from the combustion of diesel based fuel to be used by the heavy machinery in the area. The combustion will lead to the production of nitrogen oxides and even carbon monoxide.
Fugitive dust will be another expected pollutant in the area. The levels of both the nitrogen oxides and the carbon monoxide are expected to be well below state and the federal ambient standards for air quality. However nitrogen oxide is a known precursor to ozone and any increased production of the same is treated as significant.
Due to that reason equipment approved by the CARB-California Air Resources Board through PERP-Portable Equipment Registration Program will be utilized. Moreover mitigative measures will be taken to control fugitive dust generation by use of water and even soil stabilizers. The impact here is significant, short term and unavoidable (California Department of Water Resources 104).
In an effort to improve accessibility in roads will be made. These will increase the amount of dust generated. This impact would be tackled by sprinkling water and placing gravel during the road upgrade. At the same time San Clemente Drive will require vacuum sweeping to suck up all the dust generated. The impact is expected to be significant, short term and unavoidable.
The dust generated could end up in residential areas since it might not be possible to eliminate dust generation in total. To mitigate this impact residents of the area will be provided with cards bearing the contacts of the officer in charge of corrective measures so that complains can be made directly and corrective measures implemented within 24 hours. The EIR considers this impact significant, unavoidable and short term which is true.
With all the construction bound to take place, noise levels are expected to go up. This is in respect to the machines that will be used. The EIR for instance observes that jackhammers are expected to generate noise levels of about 90 dbA-A-weighted decibels. However the noise generated in the site will be considered to have almost insignificant impact.
This is because of the long distance between the site and the residential areas which means that the noise will be greatly attenuated before reaching the receptor areas. However due to the sparse population it is not possible to say that the noise levels will be insignificant. I n that respect mitigative measure will be employed to reduce noise levels and such will include limiting the operations to day time only. The impact is graded as significant, short term and unavoidable (California Department of Water Resources 105).
Clearing the vegetation and trees in order to widen the access roads will also be another source of noise. The noise is expected to be generated by equipment used such as chain saws and gas engine. This noise will build up the noise levels in the background and will therefore have significant impact.
This will require mitigation efforts to bring the levels down. Some of the measures that the document considers include good maintenance of the equipment in use, employing best practices management, using equipment with high muffler ability as well as limiting the rate of operation and the duration of the project. The EIR considers the impact as significant unavoidable and short term (California Department of Water Resources 105).
Traffic & Circulation
According to the EIR some section of the Carmel valley road and highway 1 which are currently operating below expectation will experience increased traffic which will be significant unavoidable and short term.
The construction required to improve jeep trail and establish spur road will necessitate the closing down of the jeep trail for short periods. Since these short periods could at times last more than ten minutes this impact is considered significant, unavoidable and short term. Mitigation is however possible through various efforts.
One of the efforts to be implemented will involve the project workers who will be expected to be carpooling so as to reduce the traffic on these roads. Secondly project travels would be coordinated and planned in such a manner as to avoid peak traffic times as well as establishing a means of sharing information with the public regarding the traffic.
Thirdly, there will be need to address safety plan with regard to truck size traffic, routes ,use of flag person and even signing and striping. Lastly a traffic impact fee will be paid to mitigate the impacts in respect to Carmel Valley Road and State Highway 1(California Department of Water Resources 107).
San Clemente Drive, which will be used frequently by the project traffic passes through Sleepy Hollow which is a gated community. The drive is narrow since it is a two lane road which lacks facilities for both pedestrians and bicyclists. This will inconvenience the pedestrians and bicyclists (California Department of Water Resources 107). Though short term it will impact the quality of life of the dwellers of Sleepy Hollow and may even lead to increased accidents in the area which makes the unavoidable impact significant.
The EIR treats this issue seriously by considering that the project will involve the removal of the San Clemente Dam which will also mean removing the fish ladder and also involve the notching of the OCRD-Old Carmel River Dam as well as altering its fish ladder. All these features have a historic significance and their removal or alteration will have an unavoidable and significant impact which will be long term.
The mitigation measures will involve the preparation of HABS-Historic American Building Survey and HAER-Historic American Engineering Report. In addition interpretive and educational materials will be prepared. Every step of the mitigation will be done in consultation with the SHPO-State Historic Preservation Office (California Department of Water Resources 110).
The alterations in the historic district will lead to the loss of its visual integrity. In mitigation photos of the historic resources will be taken and documented before the construction takes off (California Department of Water Resources 111).
Using the jeep trail to bring in and take away heavy machineries from the project site will have an unavoidable and significant impact on recreation on the short term (California Department of Water Resources 113).
Even though the EIR/EIS had not put into consideration the imminent transfer of the project area to public entity once the project was completed. The conservancy went ahead and prepared an addendum to the final EIR in that regard so that the property can be preserved in its natural state and be used as a park(California Department of Water Resources 114).
The EIR/EIS puts forward several alternatives to this project. However after close scrutiny only the second alternative which proposes removal of the dam without rerouting the Carmel River would sail through several benchmarks. For instance it is the only alternative that is consistent with the twenty first division of Public Resources Code. Secondly it is also the only alternative that would qualify for funding by the conservancy.
The reason it was dropped was that it has 33 significant and unavoidable effects on the environment none of which can be mitigated to insignificance (California Department of Water Resources 80). The higher costs coupled with the risk that would be involved in the sequestration of sediment ruled out the second alternative making this project the most viable removal option.
Monitoring and Reporting
The CDWR-California Department of Water and Resources being the lead agency prepared an MMRP-Mitigation Monitoring and Reporting Program with an aim of ensuring the mitigation process goes on smoothly (California Department of Water Resources 49).
The document specifies the actions and their timing with respect to the processes of monitoring mitigating and even reporting. It goes on to specify the agencies that would implement the process as well as the agency that would enforce the processes to make sure that all actions have been taken.
After carefully reviewing the final EIS/EIR it is evident that this project will have enormous public benefits. The project is expected to not only address the dam safety but at the same time maintain and restore Carmel River‘s ecological integrity. The fish will have safe passage from Carmel River’s mouth all the way to Los Padres dam.
Moreover, 928 acres of land will be availed for the general public for leisure and enjoyment in the watershed of Carmel River (Coastal conservancy 20).
Out of the 26 environmental effects expected 23 can be mitigated and again out of the remaining 3 effects that cannot be mitigated 2 are short term. The remaining effect which is long term and with no form of mitigation available has to do with increased frequency of high concentration of suspended sediment occurring only eleven times in 41 years.
Considering the whole project as depicted on the final EIR/EIS the pros outweigh the cons meaning that the public will benefit more from the implementation of the project than they will suffer from the environmental effects of implementing the project.
Business Wire. “California American Water Issues Request For Qualifications For San Clemente Dam Removal Project.” The Street, 2011.Web. 28 Nov. 2011. Available at:
California Department of Water Resources, U.S Army Corps. “FINAL Environmental Impact Report /Environmental Impact Statement” San Clemente Dam Seismic Safety Project volume 1, Chapter 1.0 – 3.0. ND, January 2008
Chapman, Trish, Monica Hunter, Joyce Ambrosius. “Project Description.” San Clemente Dam Removal Project. ND, 2011. Print
Coastal conservancy. “Implementation Phase” San Clemente Dam Removal Project, ND, 2011. Print