Mendocino County Municipal Code Ch. 20.744 Ground Water Evaluation

It is the intent of this Chapter to establish requirements for the evaluation of the adequacy of ground water resources for development in the Town of Mendocino. This Chapter is adopted specifically to implement water policies in the Mendocino Town Plan portion of the Mendocino County General Plan Coastal Element.

(Ord. No. 3915 (part), adopted 1995.)

(Ord. No. 4395, § 2, 11-17-2017)

(1) "Adequate Water Supply" means sufficient quantities of water to support proposed uses and to maintain contiguous and surrounding uses as determined by the District or as defined by the Division of Environmental Health in its publication "Land Division Requirements," as revised.

(2) "Adjacent" means any real property parcel that shares a common border with an applicant's parcel and all surrounding parcels that are separated by a road or easement.

(3) "Adverse Effect" means depletion of the groundwater supply of hydrologically contiguous or surrounding parcels, or the lowering of water levels in existing wells, to the point where there is no longer an adequate water supply for the existing usages on the parcels; or an adverse cumulative impact, where a gradual lowering of groundwater levels will eventually lead to a depletion of the water supply. An adverse effect on the water table of a monitored well on surrounding properties shall be considered to occur if pumping at the maximum demand at the pumped well results in a water table drawdown at wells on adjacent properties which either:

(a) Amount to more than ten (10) percent of the existing drawdown at such wells under conditions of maximum day water use demand; or,

(b) Causes a decline (estimated or observed) in the existing well yield to a level which is less than ninety (90) percent of maximum day water demand for the adjacent property.

(4) "Allotment" means the maximum amount of water an applicant may extract on a daily basis, as averaged over a thirty (30) day period.

(5) "Applicant means any person as defined who applies for a groundwater extraction permit from the Mendocino City Community Services District.

(6) "Aquifer" means a body of rock, sand and gravel that contains sufficient saturated permeable material to conduct groundwater and to yield economically significant quantities of groundwater to wells and springs.

(7) "Aquifer Test" means physical testing for evaluation of an aquifer to determine the existence of an adequate water supply and to provide data for the hydrological study. Similar to a hydrological study, but generally not as complex. Test to be conducted during hydrological testing period.

(8) "Change in Use" means any change in use of property to a different use category as defined in the Mendocino Town Plan, e.g., from residential to commercial or visitor serving capacity.

(9) "Changed Circumstance" means a hydrological change that diminishes water availability within the boundaries of the Mendocino City Community Services District or any part therein.

(10) "Cleaning" means the removal of silt and other soft materials, but does not include removal of rock or rock materials.

(11) "Cone of Influence" means the depression, roughly conical in shape, produced in a water table by the extraction of water from a well at a given rate. The volume of the cone varies with the rate and duration of withdrawal of water.

(12) "Cumulative Impact" means two (2) or more individual effects which, when considered together, are considerable or which compound or increase other environmental impacts. The individual effects may be changes resulting from a single project or a number of separate projects. The cumulative impact from several projects is the change in the environment which results from the incremental impact of the project when added to other closely related past, present and reasonable foreseeable provable future projects. Cumulative impacts can result from individually minor but collectively significant projects taking place over a period of time. Cumulative impacts shall be discussed when they are significant. The discussion of cumulative impacts shall reflect the severity of the impacts and their likelihood of occurrence, but the discussion need not provide as great detail as is provided of the effects attributable to the project alone. The discussion should be guided by the standards of practicality and reasonableness. The following elements are necessary to an adequate discussion of cumulative impacts: Either:

(a) A list of past, present and reasonably anticipated future impacts, including those projects outside the control of the District, or

(b) A summary of projections contained in an adopted general plan or related planning document which is designed to evaluate regional or area-wide conditions.

(13) "Deplete" means the lowering of ground water levels in an aquifer to the point where there is no longer an adequate water supply for existing uses.

(14) "District" means the Mendocino City Community Services District.

(15) "Emergency" means a sudden, generally unexpected occurrence or set of circumstances demanding immediate action.

(16) "Groundwater" means that part of the subsurface water which is the zone of saturation, including underground streams.

(17) "Hydrological Testing Period" means such time period that may be determined by the District based upon quantity and pattern of rainfall.

(18) "Hydrology" means the science that deals with continental water (both liquid and solid), its properties, circulation and distribution, on and under the Earth's surface and in the atmosphere, from the moment of its precipitation until it is returned to the atmosphere through evapotranspiration or is discharged into the ocean.

(19) "Hydrologist" means any person with a degree in hydrology who has five (5) years professional experience in the field of hydrology or who is a registered engineer or registered geologist with five (5) years professional experience in the field of hydrology.

(20) "Hydrologically Contiguous Wells" means hydrologically contiguous or surrounding wells where there is a reasonable expectation that an impact on those wells may be created by the aquifer test or increase in water extraction.

(21) "Hydrological Study" means a study of the hydrology of a defined area.

(22) "New Development" means any project which requires a building permit according to County regulations other than those that conform to all conditions relating to water use established by County water extraction permits prior to the effective date of this Ordinance. Development of any new water source and any new development or change of use not in conformance to prior County permits shall require District approval.

(23) "Person" includes any state or local governmental agency, private corporation, partnership, individual, group of individuals, owner(s) or developer(s) of a property, subdivision, or, to the extent authorized by law, any federal agency.

(24) "Proof of Water Test" means an abbreviated hydrological quantity test conducted during the hydrological testing period used to determine "adequate water supply" as defined by this Division. Proof of water testing shall be in conformance with procedures as outlined in "Mendocino County Coastal Groundwater Development Division."

(25) "Safe Yield" means the maximum quantity of water that can be withdrawn from an aquifer during the hydrological testing period or during drought without causing an undesirable result.

(26) "Sustained Yield" means the maximum quantity of water which can be withdrawn from a water supply (well) during the hydrological testing period or a drought without causing an undesirable effect.

(27) "Water Meter" means any device used to accurately measure water that is extracted from a groundwater source.

(Ord. No. 3915 (part), adopted 1995.)

(Ord. No. 4395, § 2, 11-17-2017)

(A) A hydrological study shall be required in the Town of Mendocino for all development as defined in Section 20.608.023(C) except as provided in Section 20.744.025.

(B) Hydrological studies required by this Chapter shall be performed during the hydrological testing period by a Qualified Hydrological Consultant.

(C) Hydrological studies required by this Chapter shall be performed according to approved methods and procedures as determined by the District, or the Health Officer, and published in the Mendocino Groundwater Extraction Ordinance or the Mendocino County Division of Environmental Health's "Land Division Development Requirements" as revised.

(D) Hydrological studies shall include, but not be limited to: flow rate measurements of wells and/or springs during the hydrological testing period, monitoring of the drawdown effects on adjacent wells other than the one (1) being tested, calculation of aquifer characteristics, including safe yield, and compilation of the data into a report. This report will be reviewed and interpreted by a third party, qualified hydrologist appointed by the Health Officer or the District. Interpretation of the data in the report shall be made in the most conservative way so as to protect existing uses and insure sound groundwater management.

Qualified hydrological consultants shall certify the following:

(1) (a)

Whether or not there is an adequate water supply during the dry summer months for the proposed development.

(b) Whether or not there is an adequate water supply during drought conditions.

(2) Whether or not the development as proposed will deplete the water supply for hydrologically contiguous wells.

(3) An opinion about the cumulative impacts of the proposed water extraction on the aquifer.

(4) Other findings specified by the District or the Health Officer.

(Ord. No. 3915 (part), adopted 1995.)

(Ord. No. 4395, § 2, 11-17-2017)

New development or a new use shall not be approved if the water needs of such development, as determined by the District or Health Officer, cause any of the following to occur:

(A) The groundwater extraction would have an adverse effect on the ground water supply.

(B) The evidence shows that there is insufficient groundwater to support the change in use and/or new development.

(Ord. No. 3915 (part), adopted 1995.)

(Ord. No. 4395, § 2, 11-17-2017)

A hydrological study will not be required in cases where it has been determined by the District or Health Officer that the development will not have any foreseeable impact on hydrologically contiguous wells.

(Ord. No. 3915 (part), adopted 1995.)

(Ord. No. 4395, § 2, 11-17-2017)

For purposes of this Chapter, Second Residential Units are new developments, and subject to all of the requirements for hydrological studies or proof of water required by other sections of this Chapter.

(Ord. No. 3915 (part), adopted 1995.)