N.M. Admin. Code § 19.25.12.11

Current through Register Vol. 35, No. 21, November 5, 2024

Section 19.25.12.11 - DESIGN OF A DAM

Any person, association or corporation, public or private, the state, or the United States that is intending to construct a dam shall submit an application to construct and operate a dam and supporting documentation acceptable to the state engineer. This section primarily addresses the design and construction of embankment dams. Other types of dams shall conform to sound engineering principles and current state of the practice. Because each site, design and operating practice is unique, waivers of specific requirements in this section will be considered on a case-by-case basis. Request for waiver shall be in writing accompanied with documentation justifying the request. If the request is not justified to the satisfaction of the state engineer the request will be denied. If the supporting documentation for the design of a dam does not meet acceptable engineering standards and does not conform to these regulations, as determined by the state engineer, a quality management plan or third party review may be required by the state engineer. Construction shall not begin until the state engineer has accepted the supporting documentation and approved the application with permit conditions. The application and supporting documentation shall include the information described below.

A. Application: An application form shall be completed with original signature of the dam owner and accompanied with a filing fee in accordance with Subsection A of 19.25.12.8 NMAC. The form will be the only information available to the public before the project is approved for construction. All other supporting documentation is considered draft until accepted by the state engineer. A plan review fee in accordance with Subsection C of 19.25.12.8 NMAC shall accompany the submittal of the design report, construction drawings and specifications. A detailed estimate of the construction cost for the proposed dam and appurtenant structures shall be submitted in support of the plan review fee.

B. Water right: A water right is required for water impounded by the dam. If the dam owner has a permit for the diversion of water, documentation addressing the necessity for storage, diversion periods and release conditions for the reservoir may be required. This requirement is waived for flood control dams that do not detain water longer than 96 hours in accordance with Subparagraph (b) of Paragraph (7) of Subsection C of 19.25.12.11 NMAC or provide documentation that a waiver by the state engineer has been granted. Flood control dams that do not drain within 96 hours require a water right for water permanently stored beyond the 96-hour drain time requirement and for associated losses due to evaporation and other potential depletions to the system unless a waiver in accordance with 19.25.12.11 NMAC is obtained.

C. Design report: A design report, which includes information to evaluate the safe design of the dam and appurtenant structures, shall be submitted in a form acceptable to the state engineer. The final design report shall also be submitted in an electronic format acceptable to the state engineer. The design report may be submitted as a single report or as individual reports documenting the information described below. A professional engineer licensed in the state of New Mexico qualified in the design and construction of dams shall prepare or supervise the preparation of the design report. The front cover shall show the name of the dam, the county in which the dam is located, the dam owner and the type of report. The first page behind the front cover shall show the name of the dam, the county in which the dam is located, a signed certification from the engineer and a certification for the state engineer in accordance with Subsections B and E of 19.25.12.12 NMAC. The design report shall contain the information described below and any other additional information determined necessary by the state engineer to evaluate if the design is safe.

(1) Hazard potential classification. A hazard potential classification shall be based on the dam failure condition that results in the greatest potential for loss of life and property damage. If the state engineer concurs, the classification may be based on the judgment and recommendation of the professional engineer. For all other cases, a low or significant hazard potential classification shall be supported by a dam breach and flood routing analysis, which includes calculations and data that supports the predicted dam failure flood. This analysis shall also address the potential for foreseeable future development. Evaluation of the effects of flooding from dam failure shall extend at least to the location downstream where the classification can be properly identified. The dam breach and flood routing analysis shall include, but not be limited to:

(a) description of the dam breach and flood routing methodology;

(b) a tabulation and justification of parameters used in the analysis;

(c) a sensitivity analysis of the parameters used in the analysis;

(d) references to all computer models, data and supporting justification used in the analysis;

(e) appropriate data sheets, computer program input and output computations and electronic files from computerized analysis;

(f) table of results for the flood routing for the sunny day failure and the failure and no failure scenarios for multiple flood events up to and including the spillway design flood as defined in Subparagraph (a) through (d) of Paragraph (3) of Subsection C of 19.25.12.11 NMAC; the table of results for all critical locations downstream shall include the depth of flow in feet, velocity of flow in feet per second, rate of flow in cubic feet per second and the incremental impacts; and

(g) dam failure inundation maps downstream of the dam for the sunny day failure and failure during the spillway design flood event showing the depth of flow in feet, average velocity in feet per second and rate of flow in cubic feet per second at critical locations downstream.

(2) Hydrologic analysis. The hydrologic analysis shall include a discussion of methodology used to calculate the spillway design flood for determining the available flood storage and spillway capacity. Consideration of how the dam will perform under these hypothetical flood conditions shall be evaluated. The hydrologic analysis shall include, but not be limited to:

(a) a topographic map of the drainage area above the dam with the drainage area and sub-basins delineated and presented on a map of appropriate scale and size;

(b) a description of the topography, soils and vegetative cover and land treatment of the drainage area;

(c) a discussion of the depth, duration and distribution of the spillway design storm;

(d) a tabulation, discussion and justification of all hydrologic parameters and methodology used to calculate runoff from rainfall;

(e) a discussion of the peak inflow, volume of runoff and maximum reservoir water level elevation for the inflow hydrograph;

(f) a plot of the reservoir inflow and outflow hydrographs extended until flow is negligible and plotted on the same figure of appropriate size and scale;

(g) a table showing the reservoir area (in acres) and storage capacity (in acre-feet) for each foot of elevation above the bottom of the reservoir to the dam crest; the table shall be determined from the reservoir topography map; indicate the amount of dead storage, elevation of the invert of the outlet and elevation of the crest of each spillway; all elevations shall be based on North American vertical datum 1988 or more recent adjustment; and

(h) appropriate data sheets and computer program output computations from computerized analysis.

(3) Spillway design flood. The spillway design flood is the flood that a spillway must be capable of conveying without dam failure. For perimeter embankment dams with no spillway and no external drainage area, the dam must be capable of impounding the spillway design flood without dam failure. A spillway design flood less than these requirements is acceptable to the state engineer if an incremental damage analysis is presented to justify the inflow design flood in accordance with Paragraph (4) of Subsection C of 19.25.12.11 NMAC. The spillway design flood is based on size classification and hazard potential classification of the dam as described below.

(a) Dams classified as low hazard potential, regardless of size, shall have spillways designed to pass a flood resulting from a 100-year precipitation event expressed as a percentage of the probable maximum precipitation.

(b) Dams classified as small and intermediate, with a significant hazard potential rating shall have spillways designed to pass a flood resulting from 50 percent of the probable maximum precipitation.

(c) Dams classified as large, with a significant hazard potential rating shall have spillways designed to pass a flood resulting from 75 percent of the probable maximum precipitation.

(d) Dams classified as high hazard potential, regardless of size, shall have spillways designed to pass a flood resulting from the probable maximum precipitation.

(4) Incremental damage assessment. Where spillways are not in compliance with Paragraph (3) of Subsection C of 19.25.12.11 NMAC an incremental damage assessment shall justify the inflow design flood used to size the spillway. The spillway design flood from an incremental damage assessment is the flood above which the incremental increase in downstream water surface elevation due to failure of a dam is no longer considered to present an unacceptable additional downstream threat when compared to the same flood without dam failure. The lower limit is the flood resulting from the 100-year precipitation. The assessment shall compare the incremental impacts on downstream areas including existing and foreseeable future development. The assessment shall include a dam breach and flood routing analysis in accordance with Subparagraphs (a) through (g) of Paragraph (1) of Subsection C of 19.25.12.11 NMAC for the failure and non-failure conditions. Methods for assessing the damage between failure and non-failure conditions shall be fully documented.

(5) Spillway capacity. The spillway capacity shall be adequate to pass the spillway design flood in accordance with Paragraph (3) of Subsection C of 19.25.12.11 NMAC or accepted inflow design flood in accordance with Paragraph (4) of Subsection C of 19.25.12.11 NMAC without failure of the dam. If the outlet works are gated, the design discharge of the outlet works shall not be considered when routing the spillway design flood through the reservoir and spillway. The water level shall be at the normal operating level at the beginning of the spillway design storm. A spillway rating curve and table showing elevation in one-foot increments versus maximum discharge capacity shall be prepared. The rating curve and table shall include data from the crest of the spillway to the dam crest. The parameters used to calculate the spillway capacity shall be justified and appropriate data sheets and computer program output computations from computerized analysis shall be provided. Elevations shall be based on North American vertical datum 1988 or more recent adjustment.

(6) Spillway design. Spillways shall be evaluated for erosion potential during normal operation and the design flood event. Damage to a spillway during the design flood event is acceptable; however, a breach of the spillway is unacceptable. The spillway design shall address the minimum requirements described below.

(a) The material required for spillway lining depends on the spillway location, frequency of discharge and velocity of discharge to adequately address erosion and breach potential. The design shall provide adequate justification for the material selected.

(b) The design shall provide aeration of the nappe for cavitation control where control weirs are used at the spillway crest.

(c) The spillway must discharge away from the toe of the dam and abutment slopes.

(d) The design shall address the potential for the accumulation of debris that may block the spillway.

(e) The design shall address energy dissipation to adequately control erosion of the natural channel due to spillway discharge reasonably expected to occur during the life of the dam.

(f) Channel lining shall be placed on a suitably prepared, stable subgrade. All edges and joints in channel lining material must be designed to prevent undermining and erosion. Concrete channel lining must be provided with adequate jointing to permit thermal expansion and contraction and adequate reinforcing to control thermal cracking. Adequate water stops are required at joints in the spillway lining. Concrete lining shall be adequately anchored against displacement and uplift and shall be provided with adequate subdrainage to relieve hydrostatic pressure and prevent frost heave.

(g) Where training dikes are used to divert the water away from the dam, the dike shall be designed with a compaction to at least 95% of the maximum standard Proctor density, ASTM D 698, or at least 90% of the maximum modified Proctor density, ASTM D 1557. Erosion protection for the dike shall be addressed in accordance with Paragraph (16) of Subsection C of 19.25.12.11 NMAC.

(7) Outlet works capacity. Dams shall be designed with a low level outlet to drain the entire contents above the elevation of the downstream toe of the dam. If environmental consequences prevent draining of the reservoir, the state engineer will grant a waiver if written justification is provided to the satisfaction of the state engineer. The outlet shall be sized to provide adequate capacity to satisfy water rights of downstream priority users. A stage discharge curve and table showing elevation in one-foot increments versus discharge capacity shall be prepared. The rating curve and table shall be from the invert of the outlet to the dam crest. The parameters used to calculate the outlet works capacity shall be justified and appropriate data sheets and computer program output computations from computerized analysis shall be provided. Elevations shall be based on North American vertical datum 1988 or more recent adjustment. The outlet works capacity shall meet the minimum requirements described below.

(a) Outlets for water storage dams shall drain the reservoir in 45 days with supporting calculations provided.

(b) Outlets for flood control dams shall drain the reservoir in 96 hours unless a waiver is granted by the state engineer. The 96-hour time frame begins once the reservoir storage drops to the emergency spillway crest or reaches its peak during the 100-year, 24-hour event. Documentation supporting the waiver shall include the time to drain more frequent events.

(8) Outlet works design. The outlet works design includes the intake structure, conduit and terminal structure. The outlet works design shall meet the minimum requirements described below.

(a) Minimum conduit diameter is 18 inches unless a waiver is granted by the state engineer. Documentation supporting a waiver shall include identification of methods to inspect the interior of the conduit.

(b) Metal conduits used in dams that are classified as significant hazard potential where the sole purpose of the dam is flood control, or in dams classified as low hazard potential, shall have adequate strength after corrosion for a minimum of 200 years, based on corrosivity testing of onsite soils. Cathodic or other protection of metal conduits is permissible and may be considered in this analysis. Metal conduits are not acceptable for dams classified as high hazard potential or dams classified as significant hazard potential with permanent water storage except as interior forms for cast-in-place concrete conduits.

(c) Outlet conduits for storage reservoirs shall be gated at the upstream end unless a waiver is granted by the state engineer. Where gates are located other than at the upstream end of the conduit, a guard gate or bulkhead shall be provided at the upstream end to allow draining of the conduit for inspection, maintenance and repair.

(d) Outlet conduits shall be adequately vented and shall include all supporting calculations. Where the outlet conduit ties directly to a downstream pipe, a by-pass valve shall be provided. An exception to the by-pass valve will be granted when the conduit discharges to an ungated downstream storm drain with adequate access for inspection and maintenance.

(e) Outlet controls and equipment shall be properly designed to be secure from damage due to vandalism, weather, ice, floating debris, wave action, embankment settlement and other reasonably foreseeable causes. The outlet control operators shall remain accessible during outlet works and spillway releases.

(f) Outlets for flood control structures shall be ungated. Where a gate is required to satisfy downstream release restrictions, a waiver from the state engineer is required. The written request for waiver shall include a plan for timely release of the floodwater.

(g) Outlet works intake structures shall be provided with trash racks or grates to prevent clogging with debris. Grate opening area or bar spacing shall be adequate to satisfy applicable public safety requirements, if appropriate. Total area of grate openings must be at least three times the cross-sectional area of the outlet conduit.

(h) The design of the outlet works terminal structure shall address energy dissipation to prevent erosion and shall include supporting calculations.

(i) Outlet conduits shall be designed for full embankment loading and for hydrostatic pressure equal to the maximum reservoir head, acting separately and in combination, with an adequate factor of safety for the conduit material. If future increases in embankment height or reservoir head are foreseeable, allowance shall be made in the design.

(j) The conduit together with all joints and fittings shall be watertight at the design pressure and shall be pressure tested prior to backfilling. Conduits shall be designed for all reasonably foreseeable adverse conditions including corrosion, abrasion, cavitation, embankment settlement and spreading, thermal effects and seismic loading. The ability of the conduit to withstand deflection and separation at the joints shall be addressed in the design of the outlet conduit.

(k) Outlet works shall be supported by stable, well-consolidated foundation materials. Where the conduit is placed in embankment fill or native overburden materials, settlement analysis shall be performed.

(l) Minimizing seepage along conduits shall be addressed including the methods for ensuring compaction of backfill around and beneath the conduit. Seepage collars are not an acceptable design standard for controlling seepage.

(m) All supporting documentation and calculations for the outlet works design shall be provided. The outlet works design shall include all foreseeable loading conditions, including but not limited to ice loading, debris buildup, wave action and embankment settlement. Structural design calculations for the intake structure, conduit and outlet structure shall be submitted.

(9) Geological assessment. A geological assessment of the dam and reservoir site is required for all dams classified as high or significant hazard potential. The geological assessment may be included in the geotechnical investigation or seismic study, or may be submitted as a separate document. The geological assessment shall address regional geologic setting; local and site geology; geologic suitability of the dam foundation; slide potential of the reservoir rim and abutment areas; and seismic history and potential.

(10) Geotechnical investigation. A geotechnical investigation shall assess site conditions and support the design. A professional engineer licensed in the state of New Mexico qualified to provide geotechnical expertise in the design and construction of dams shall prepare, stamp and sign the geotechnical investigation, which may be submitted as a separate report. The scope of the geotechnical investigation is dependent on the size classification, hazard potential classification, anticipated materials and construction methods, site geology and seismicity, anticipated soil strata and other site-specific conditions. The geotechnical investigation shall include a field investigation and laboratory testing. Results of field and laboratory testing shall be presented in a report, including recommended parameters to be used in design and construction of the dam and appurtenant structures. The field investigation and laboratory testing shall include but not be limited to the following:

(a) test borings in the footprint of the embankment, spillway excavations and appurtenant structures extending to bedrock or to a depth equal to at least the height of the dam; where appropriate, borings may include coring of bedrock materials to determine the quality and character of the rock;

(b) standard penetration tests or other field-testing to assess soil character and consistency;

(c) "undisturbed" sampling for further tests such as insitu density, shear strength and compressibility;

(d) supplemental test pits, if deemed necessary, to obtain bulk and undisturbed samples, assess soil layering and measure bedrock orientation;

(e) measurement of water level in drill holes;

(f) field permeability testing, if feasible;

(g) logs of test borings and test pits, location map and profile along dam axis with soil information shown;

(h) testing to determine the relevant properties of the material to be used in construction, including but not limited to shear strength, permeability, compressibility and filter characteristics; the testing method shall conform to accepted industry standards and be appropriate for the material being tested;

(i) evaluation of liquefaction potential and dynamic shear strength testing if deformation analysis is required; and

(j) identification of the location of the borrow material to be used during construction.

(11) Seepage and internal drainage. The effects of seepage and potential for internal erosion shall be evaluated. For dams with aesthetic fill on the downstream slope, the effects of seepage shall be evaluated with and without the aesthetic fill. A seepage analysis shall be performed to address the performance of the embankment under steady-state conditions for dams classified as high or significant hazard potential. All parameters and assumptions used in the analysis shall be summarized in a table and justified in the seepage analysis. A waiver may be requested in writing for flood control dams that drain in 96 hours. The seepage analysis and internal drainage design shall include the minimum requirements described below.

(a) Flow nets of appropriate size and scale shall be prepared. The effects of anisotropy with respect to permeability shall be addressed. Ratios of horizontal to vertical permeability of less than 4 for constructed embankments and less than 9 for native deposits shall be supported by field and laboratory permeability tests. Appropriate data sheets and computer program output computations from computerized analysis shall be provided.

(b) The design shall address the effects of anticipated seepage beneath, around and through the dam. Seepage shall not exit on the dam face and excessive exit seepage gradients are unacceptable. All filter, transition and drainage zones within earth dams shall have a thickness adequate to address constructability and enhance seismic stability with a minimum thickness of 3 feet for each zone.

(c) Collector pipes and conduits for internal drains shall be made of non-corrodible material capable of withstanding the anticipated loads. If possible, pipes shall be located where they can be exposed for repair or replacement without threatening the stability of the dam. Collector pipes for drains shall be enveloped in a free-draining medium meeting filter criteria for adjacent embankment or foundation zones. Where surging or hydraulic gradient reversal is likely, perforation size must be less than the diameter at which 15 percent of the surrounding medium is finer. Where surging or hydraulic gradient reversal are unlikely, the perforation size must be less than the diameter at which 85 percent of the surrounding medium is finer.

(d) Drain pipes shall be sized to provide a flow depth no more than 1/4 of the pipe diameter when carrying the anticipated discharge. Drain pipes shall be at least 6 inches in diameter unless the availability of technology for inspection and maintenance can be demonstrated. Individual pipes shall discharge to a gallery, well, manhole, or to daylight such that the flow of each pipe can be monitored and measured. Manifold connections, tees and wyes are not permitted. A seepage measuring device must be appropriate for the rate of anticipated flow. The measuring device must include an upstream catchment to detect any sediment in the seepage. Where pipes from internal drains are discharged to daylight, a rodent screen shall be provided.

(12) Stability analysis. Cross-sectional design for dams shall be supported by slope stability analysis. For dams with aesthetic fill on the downstream slope, the stability of the downstream slope shall be evaluated with and without the aesthetic fill. Dams classified as low hazard potential with upstream slopes no steeper than 3 horizontal to 1 vertical, downstream slopes no steeper than 2 horizontal to 1 vertical and which are 25 feet or less in height will not require slope stability analysis. Stability analysis of the reservoir rim is required where slopes are steeper than 3 horizontal to 1 vertical. The analysis model shall adequately represent the geometry and zoning, shear strength parameters, material unit weights, pore pressure and seepage conditions, external loading and other relevant factors of the critical cross section or sections. Manual computations in the analysis will be accepted if judged to be sufficiently rigorous. Where appropriate, the analysis shall consider noncircular or block and wedge type failure surfaces as well as circular failures. All parameters and assumptions used in the analysis shall be summarized in a table and justified in the geotechnical investigation. A scale drawing, utilizing the same scale for vertical and horizontal dimensions, shall be provided for each cross-sectional model used in the analysis, with the critical failure surface(s) identified. Appropriate data sheets and computer program output computations from computerized analysis shall be provided. Dams shall be designed to provide the following minimum factors of safety from the stability analysis:

(a) 1.5 for steady state long-term stability;

(b) 1.5 for operational drawdown conditions;

(c) 1.3 for rapid drawdown conditions; and

(d) 1.3 for end of construction.

(13) Seismic design and analysis. Dams and appurtenant structures classified as high or significant hazard potential shall be analyzed for seismic stability. Seismic analysis for water storage dams shall be based on full reservoir under steady state seepage conditions. Flood control dams with ungated outlets that satisfy Subparagraph (b) of Paragraph (7) of Subsection C of 19.25.12.11 NMAC without waiver shall be designed for earthquake loads under empty reservoir conditions and need not consider steady-state seepage. Dams sited on active faults shall obtain a waiver from the state engineer. To obtain a waiver the analysis shall show that the location of the dam is unavoidable and the dam must be designed to withstand anticipated fault movement without compromising its integrity. Appropriate data sheets and computer program output computations from computerized analysis shall be provided. The seismic analysis shall meet the minimum requirements described below.

(a) A seismological investigation for the dam area and reservoir area shall be performed. This study may be part of the geological or geotechnical report for the structure, or may be a separate effort. The study shall determine and justify the appropriate seismic parameters to be used for design. The dam and appurtenant structures shall be capable of withstanding the operating basis earthquake with little to no damage and without interruption of function. The operating basis earthquake has a 50% probability of exceedance during the service life of the dam or appurtenant structures. In no case shall the service life be less than 100 years. The dam and appurtenant structures critical to the safety of the dam shall be capable of withstanding the design earthquake without failure. The seismic parameters shall be based on the design earthquake requirements described below.

(i) Dams classified as high hazard potential other than flood control structures shall be designed for the maximum credible earthquake or for a 1% probability of exceedance in 50 years (approximately 5000-year return frequency).

(ii) Dams classified as significant hazard potential or high hazard potential dams whose sole purpose is for flood control shall be designed for a 2% probability of exceedance in 50 years (approximately 2500-year return frequency).

(b) An analysis of materials in the foundation, reservoir area and proposed embankment shall be completed to determine the potential for liquefaction, earthquake-induced sliding, or other seismic sensitivity, which may be accomplished as part of the geotechnical investigation.

(c) Pseudostatic analysis will be acceptable for the following cases:

(i) the embankment is to be mechanically compacted to at least 95% of the maximum standard Proctor density, ASTM D 698, or at least 90% of the maximum modified Proctor density, ASTM D 1557; no materials prone to liquefaction are present in the foundation and peak ground acceleration is 0.20g or less; or

(ii) the embankment is to be mechanically compacted to at least 95% of the maximum standard Proctor density, ASTM D 698, or at least 90% of the maximum modified Proctor density, ASTM D 1557; potentially submerged portions of the embankment except for internal drain elements are constructed of clayey material; the dam is constructed on clayey soil or bedrock foundation and peak ground acceleration is 0.35g or less; and

(iii) all safety factor requirements in accordance with Subparagraphs (a) through (d) of Paragraph (12) of Subsection C of 19.25.12.11 NMAC are met;

(iv) minimum freeboard requirements in accordance with Subparagraphs (a) through (e) of Paragraph (15) of Subsection C of 19.25.12.11 NMAC are met; and

(v) the pseudostatic coefficient selected for analysis must be at least 50% of the predicted peak ground acceleration, but not less than 0.05g and the factor of safety under pseudostatic analysis shall be 1.1 or greater. In determining the factor of safety for pseudostatic analysis, a search for the critical failure surface shall be made.

(d) For dams not satisfying the requirements for pseudostatic analysis, a deformation analysis is required. The resulting embankment must be capable of withstanding the design earthquake without breaching and with at least 3 feet of freeboard remaining after deformation. The analysis shall also assess the potential for internal erosion as a result of cracking during deformation.

(14) Dam geometry. The dam geometry shall be supported by the stability and seismic analysis and shall meet the minimum requirements described below.

(a) The crest width shall be at least equal to the dam height in feet divided by 5 plus 8 feet, with the minimum permissible crest width being 10 feet and the maximum required crest width being 24 feet.

(b) Roads located on the crest shall have appropriate surfacing to provide a stable base that resists rutting and provides adequate friction for safety in wet conditions.

(c) The crest design shall provide a minimum of 2 feet of cover or the depth of frost penetration; whichever is greater, above clay cores to prevent cracking of the core due to desiccation or frost penetration.

(d) Turnarounds shall be provided on dead-end service roads on dam crests, located in such a manner that backing maneuvers longer than 300 feet are eliminated.

(e) The crest shall be provided with adequate cross slope to prevent ponding.

(f) The slope or slopes to which crest drainage is directed must be provided with adequate erosion protection to accept the crest drainage.

(g) The crest longitudinal profile shall be provided with adequate camber to maintain the profile after embankment settlement. Camber shall be based on a settlement analysis and shall be at least 2 percent of the total embankment height, with a minimum of 1 foot at the highest point of the dam. The tops of internal core zones shall also be provided with camber in a similar manner to the crest of the dam.

(h) In the event that safety berms, street curbs, or other longitudinal features which block, control, or concentrate drainage are required on the dam crest, the design shall provide for collection and conveyance of accumulated water to discharge away from the embankment without erosion.

(15) Freeboard. Dams shall be provided with adequate freeboard. Wave runup shall be determined taking into consideration wind speed, reservoir fetch, embankment slope and roughness of the slope surface. Freeboard shall satisfy the minimum requirements described below.

(a) Anticipated wave runup resulting from a 100 mph wind with reservoir level at the spillway crest will not overtop the dam.

(b) Anticipated wave runup resulting from a 50 mph wind with maximum reservoir level from routed spillway design flood will not overtop the dam.

(c) Clay core cover and capillary rise requirements in accordance with Subparagraph (c) of Paragraph (14) of Subsection C of 19.25.12.11 NMAC are satisfied.

(d) A minimum of 3 feet of freeboard remains after seismic deformation.

(e) In any case, at least 4 feet of freeboard shall be provided. The minimum of 4 feet of freeboard may be waived for perimeter embankment dams with no spillway and no external drainage area, provided a written request is made to the state engineer accompanied with supporting justification.

(16) Erosion protection. Erosion protection shall be addressed to protect the dam and appurtenant structures from erosion that can threaten the safety of the structure. Erosion protection shall address the minimum requirements described below.

(a) Wave erosion. The upstream slope shall be protected from wave erosion. The material selected and area of coverage shall be appropriate for the protection required with justification provided. Flood control dams in compliance with Subparagraph (b) of Paragraph (7) of Subsection C of 19.25.12.11 NMAC without waiver are exempt from wave protection.

(b) Surface erosion. The slope, crest, abutment and groins, toe areas and any other constructed areas associated with the dam and appurtenant structures shall be protected from wind erosion and erosion from concentrated and sheet flows. The material selected and area of coverage shall be appropriate for the protection required with justification provided.

(17) Geotextile design. Geotextiles are an acceptable material for use in dam design only if the geotextile is placed so that it does not jeopardize the dam or appurtenant structures during repair or failure of the geotextile. The geotextile shall be used in accordance with the manufacturer's recommendations and intended use for the product. Geotextile design computations shall be provided. Where a geotextile is used for fluid containment the installation shall be performed by certified personnel and the completed installation shall be certified by a qualified independent entity.

(18) Structural design. The structural design information for all appurtenant structures, addressing water, earth, ice and any other applicable load shall be provided. Reinforced concrete design including assumptions for loads and limiting stresses and sample calculations shall be provided. Appropriate data sheets and computer program output computations from computerized analysis shall be provided.

(19) Utilities design. Utility placement or relocation shall be addressed as applicable. Utilities located in the vicinity of the proposed embankment, spillway and seepage footprint should be relocated and trenches backfilled and compacted with suitable material to the satisfaction of the state engineer. If utilities are allowed to remain, they will be required to satisfy applicable provisions for outlet conduits in accordance with Paragraph (8) of Subsection C of 19.25.12.11 NMAC.

(20) Miscellaneous design. Because each design is unique, all design elements not specifically addressed in these regulations shall be documented and justified with sample calculations and appropriate data sheets and computer program output computations from computerized analysis shall be included in the design report.

D. Construction drawings: Construction drawings shall be submitted in a form acceptable to the state engineer. The final construction drawings shall also be submitted in an electronic format acceptable to the state engineer. A professional engineer licensed in the state of New Mexico qualified in dam design and construction shall prepare the construction drawings. Illegible, mutilated, careless or otherwise poorly prepared drawings are not acceptable for filing with the state engineer. The construction drawings shall contain the information described below and any other additional information determined necessary by the state engineer to evaluate if the construction drawings are consistent with the design.

(1) Quality. Construction drawings and maps shall be made from actual field or photogrammetric surveys of an accuracy acceptable to the state engineer. Construction drawings and maps shall be prepared with permanent black ink on mylar. All original signatures, dates and acknowledgments appearing on the sheet(s) shall be in permanent ink. Construction drawings and maps shall always be rolled, never folded, for transmittal.

(2) Scale and size. Sheets shall range in size from twenty-two (22) to twenty-four (24) inches by thirty-four (34) to thirty-six (36) inches with one (1) inch margins on all sides. The scale(s) used on the drawings may vary according to requirements and space available to show all necessary data in detail clearly in feet and decimals and to be clearly legible when the drawings are reduced to eleven (11) inches by seventeen (17) inches. Detailed dimensions of appurtenant structures shall be given in feet and inches. All sheets shall have bar scales in order to allow scaling of reduced drawings.

(3) Sheet numbers. Each sheet shall be numbered sequentially with the first sheet being sheet number one in conjunction with the total numbered sheets (example Sheet 1 of 5). The sheet number on the last sheet shall equal the total number of sheets.

(4) Engineer's seal and signature. Each sheet shall have the responsible engineer's seal and signature.

Seals and signatures shall be presented in accordance with 16.39.3 NMAC.

(5) Orientation and date. The direction of north and the basis of bearings shall be shown on all maps. The date that field surveys are made or the date of the aerial photography used shall be shown on the maps.

(6) Title sheet. The first sheet of a set of construction drawings is the title sheet. The title sheet shall only contain sufficient information to summarize the scope of the project, the title of the project, signed certifications from the dam owner, engineer and a certification for the state engineer in accordance with Subsections A, B and E of 19.25.12.12 NMAC. The title sheet shall summarize the properties of the dam and shall include the following information, as appropriate:

(a) name of the dam (same as shown on the application);

(b) type of dam (material);

(c) hazard potential classification;

(d) maximum height above the downstream toe in feet;

(e) maximum length in feet;

(f) crest width in feet;

(g) slope of the upstream face (horizontal to 1 vertical);

(h) slope of the downstream face (horizontal to 1 vertical);

(i) elevation of the dam crest in feet;

(j) elevation of spillway crest in feet;

(k) length of the conduit in feet;

(l) invert elevation of the upstream end of the conduit in feet;

(m) invert elevation of the downstream end of the conduit in feet;

(n) freeboard in feet;

(o) residual freeboard in feet;

(p) maximum spillway discharge capacity in cubic feet per second;

(q) type of outlet conduit (give size and material);

(r) maximum outlet conduit discharge capacity in cubic feet per second; and

(s) location of the outlet works intake structure (using latitude and longitude in decimal degrees at least to the fifth place after the decimal).

(7) Vicinity map. A vicinity map of sufficient scale and size to locate the pertinent area shall be shown on the title sheet or second sheet of the drawings.

(8) Site topography. A detailed topography of the dam site including sufficient area upstream and downstream and at the abutments shall be provided. Elevations shall be based on North American vertical datum 1988 or more recent adjustment.

(9) Design details. Detailed information of the various construction features including plan view, elevations, cross-sections at the maximum section and along the outlet works, profile along and section through the centerline of the dam showing the foundation materials, construction features and cross-sections and a profile of the emergency spillway with dimensions and construction details shall be provided. Any other information necessary for the state engineer to determine the feasibility and safety of the dam shall be provided.

(10) Reservoir area, capacity and high water line traverse. The topography of any proposed reservoir site shall be determined to industry standards and a contour map with a contour interval of 1 foot shall be prepared. Elevations of the contours shall be tied to the North American vertical datum of 1988 or more recent adjustment. The elevation of the high water line will be highlighted on the contour map. A curve and table of elevation versus area and storage capacity for the reservoir shall be prepared from the contour map. The curve and table shall be from the bottom of the reservoir to the dam crest. Area shall be provided in acres and storage capacity in acre-feet.

(11) Permanent bench mark. A permanent bench mark shall be established above the high water line at a location unlikely to settle or be disturbed. The North American vertical datum of 1988 or more recent adjustment for the bench mark elevation and the latitude and longitude in decimal degrees at least to the fifth place after the decimal for the bench mark location shall be provided. A detail of construction of the permanent bench mark shall be provided.

E. Specifications: A specification package shall be prepared for each project describing work to be done and materials to be used to supplement construction drawings. Specifications shall be submitted in a form acceptable to the state engineer. The specifications shall also be submitted in an electronic format acceptable to the state engineer. Reference to standard technical specifications is not acceptable. Inclusion of appropriate specification sections derived from model specifications is acceptable. Specifications must be clear and concise. Specifications shall include detailed methods of construction, qualities and sizes of materials, unit amounts to be used, methods and frequency of testing and quality control, construction supervision and frequency of inspection. Specifications shall be prepared by a professional engineer licensed in the state of New Mexico qualified in the design and construction of dams. The specifications shall contain the information described below and any other additional information determined necessary by the state engineer to evaluate if the construction methods are consistent with the design and construction drawings.

(1) The front cover of the specifications shall show the name of the dam (identical to the application) and the county in which the dam is located. The first page behind the front cover shall show the name of the dam (identical to the dam name on the application), the county in which the dam is located, a signed certification from the engineer and a certification for the state engineer in accordance with Subsections B and E of 19.25.12.12 NMAC.

(2) The specifications shall include a table of contents.

(3) The specifications shall be bound and submitted on 8 1/2-inch by 11-inch white paper.

(4) The general conditions shall include a statement that the construction drawings and specifications cannot be changed without the prior written approval of the state engineer and must recognize the authority of the state engineer to perform inspections during construction. An approved model statement is provided below. Changes to the model statement require prior approval of the state engineer. "All construction shall be performed in strict accordance with the accepted construction drawings and specifications. Changes to the accepted construction drawings or specifications require prior written approval of the state engineer. Representatives of the state engineer shall have full authority to perform inspections during construction and shall have full power to act pursuant to the law and in accordance with Title 19, Chapter 25, Part 12, Dam Design, Construction and Dam Safety of the New Mexico Administrative Code if construction drawings and specifications are not followed."

F. Boundary, easement or right of way plat of survey: A plat of survey shall be submitted in a form acceptable to the state engineer. A professional surveyor licensed in the state of New Mexico shall prepare a plat of survey showing the dam owner's property boundaries or easement or right of way granted by the land owner. The plat of survey shall be prepared in conformance with the requirements as set forth in the Minimum Standards for Surveying in New Mexico, 12.8.2 NMAC. The plat of survey shall clearly state to whom an easement is granted and what rights are conveyed with the easement. The plat of survey shall show the footprint of the dam and appurtenant structures and the high water line in the reservoir. The plat of survey shall be recorded with the county clerk of the county or counties in which the survey is located. A certificate signed by the surveyor in accordance with Subsection C of 19.25.12.12 NMAC shall appear on the plat of survey. A certified copy of the recorded plat of survey bearing the recorded page and endorsement of the county clerk shall be submitted to the state engineer for filing. Adequate property ownership, easement or right of way shall be required for the following conditions:

(1) to access the dam and outlet controls during normal and flood events;

(2) to prevent development encroachment into the reservoir area defined by normal operation and the spillway design flood that adversely affects the performance of the dam;

(3) to prevent development in the approach, control and discharge section of the spillway that may restrict flow through the spillway;

(4) to return outlet works and spillway discharge to the natural drainage and allow the outlet works to discharge freely; and

(5) to perform maintenance on the dam, appurtenant structures and surrounding areas to ensure the safe performance of the dam.

G. Dam site security: Dams classified as high or significant hazard potential shall address security at dams to prevent unauthorized operation or access. If in the opinion of the state engineer, the failure of the dam will result in catastrophic consequences, a security and risk management program for the dam will be required. Elements of a security and risk management program are:

(1) threat, vulnerability and risk assessments;

(2) physical security plans; and

(3) integration of security operational procedures.

H. Instrumentation plan: An instrumentation plan shall be submitted in a form acceptable to the state engineer. An instrumentation plan providing the ability to monitor and evaluate the performance of a dam is required for dams classified as high or significant hazard potential. Instrumentation details must be included on construction drawings and specifications must be consistent with the instrumentation plan. The instrumentation plan may be submitted as a separate report or as part of the design report. Minimum requirements of the instrumentation plan shall include:

(1) description and purpose;

(2) detailed description of installations;

(3) calibration and maintenance schedule and instructions;

(4) reading schedule and instructions;

(5) data reduction and interpretation instructions; and

(6) identification of critical readings.

I. Operation and maintenance manual: An operation and maintenance manual is required for dams classified as high or significant hazard potential. The operation and maintenance manual identifies activity necessary to address the continued safe operation, maintenance and overall performance of the dam. Any restrictions imposed by the design shall be addressed in the operation and maintenance manual. The operation and maintenance manual shall conform to the requirements set forth in 19.25.12.17 NMAC.

J. Emergency action plan: An emergency action plan is required for dams classified as high or significant hazard potential. The emergency action plan identifies potential emergency conditions at a dam and specifies preplanned actions to be followed to minimize property damage and loss of life. The emergency action plan shall conform to the requirements set forth in 19.25.12.18 NMAC.

N.M. Admin. Code § 19.25.12.11

19.25.12.11 NMAC - N, 3/31/2005; A, 12/31/2010